71M6521BE-IGT/F - Maxim Integrated

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

GENERAL DESCRIPTION

The TERIDIAN 71M6521BE is a highly integrated SOC with an MPU core,

FLASH and LCD driver. TERIDIAN’s patented Single Converter Technol-

ogy™ with a 22-bit delta-sigma ADC, four analog inputs, digital temperature

compensation, precision voltage reference, battery voltage monitor, and 32-

bit computation engine (CE) supports a wide range of residential metering

applications with very few low-cost external components. A 32kHz crystal

time-base for the entire system further reduces system cost. The IC

supports 2-wire single-phase residential metering along with tamper-

detection mechanisms.

Maximum design flexibility is provided by multiple UARTs, I2C, μWire, up to

14 DIO pins and in-system programmable FLASH memory, which can be

updated with data or application code in operation.

A complete array of ICE and development tools, programming libraries and

reference designs enable rapid development and certification of AMR and

Prepay meters that comply with worldwide electricity metering standards.

MPU

TIMERS

XIN

XOUT

VREF

RX/DIO1

TX/DIO2

COM0..3

V3.3A V3.3

SYS

VBAT

V2.5

VBIAS

SEG0..18

GNDA GNDD

SEG 24..31/

DIO 4..11

SEG 34..37/

DIO 14..17

ICE

LOAD

888888.88

I2C or µWire

EEPROM

POWER

FAULT

AMR

TEST PULSE

COMPARATOR

SENSE

DRIVE/MOD

SERIAL PORTS

OSC/PLL

CONVERTER

DIO, PULSE

COMPUTE

ENGINE

FLASH

RAM

VOLTAGE REF

REGULATOR

POWER SUPPLY

TERIDIAN

71M6521BE

3.3V LCD

TEMP

SENSOR

32 kHz

NEUT

CT/SHUNT

11/14/2007

BLOAD

PWR MODE

CONTROL

WAKE-UP

BATTERY

ICE_E GNDD

V3P3D

SEG 32,33,

FEATURES

• < 0.4% Wh accuracy over 2000:1 current range

and over temperature

• Exceeds IEC62053 / ANSI C12.20 standards

• Voltage reference < 40ppm/°C

• Four sensor inputs—VDD referenced

• Low jitter Wh test output (10kHz maximum)

• Pulse count for Wh pulse output

• Tamper detection: Neutral current with CT or

shunt

• Line frequency count for time keeping

• Digital temperature compensation

• Sag detection for phase A and B

• Independent 32-bit compute engine

• 46-64Hz line frequency range with same

calibration

• Phase compensation (±7°)

• Battery monitor

• Three battery modes w/ wake-up on push-button

or timer:

Brownout mode (48µA)

LCD mode (5.7µA)

Sleep mode (2.9µA)

• Energy display on main power failure

• Wake-up with push-button

• 22-bit delta-sigma ADC

• 8-bit MPU (80515), 1 clock cycle per instruction

w/ integrated ICE for MPU debug

• Hardware watchdog timer, power fail monitor

• LCD driver (up to 140 pixels)

• Up to 14 general purpose I/O pins

• 32kHz time base

• 8KB FLASH with security

• 2KB MPU XRAM

• Two UARTs for IR and AMR

• Digital I/O pins compatible with 5V inputs

• 64-pin LQFP

• Lead Free package

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

Table of Contents

GENERAL DESCRIPTION ............................................................................................................................................1

FEATURES......................................................................................................................................................1

HARDWARE DESCRIPTION.........................................................................................................................................9

Hardware Overview..........................................................................................................................................9

Analog Front End (AFE)...................................................................................................................................9

Input Multiplexer ................................................................................................................................9

A/D Converter (ADC).......................................................................................................................10

FIR Filter..........................................................................................................................................10

Voltage References .........................................................................................................................10

Temperature Sensor........................................................................................................................ 11

Battery Monitor ................................................................................................................................12

Functional Description .....................................................................................................................12

Digital Computation Engine (CE) ................................................................................................................... 12

Meter Equations ..............................................................................................................................13

Real-Time Monitor ...........................................................................................................................13

Pulse Generator ..............................................................................................................................13

CE Functional Overview ..................................................................................................................14

80515 MPU Core ...........................................................................................................................................16

Memory Organization ......................................................................................................................16

Special Function Registers (SFRs).................................................................................................. 18

Special Function Registers (Generic 80515 SFRs) .........................................................................19

Special Function Registers Specific to the 71M6521BE ..................................................................21

Instruction Set..................................................................................................................................22

UART...............................................................................................................................................22

Timers and Counters .......................................................................................................................25

WD Timer (Software Watchdog Timer)............................................................................................27

Interrupts .........................................................................................................................................29

On-Chip Resources .......................................................................................................................................37

Oscillator..........................................................................................................................................37

PLL and Internal Clocks...................................................................................................................37

Temperature Sensor........................................................................................................................ 37

Physical Memory .............................................................................................................................37

Optical Interface ..............................................................................................................................38

Digital I/O.........................................................................................................................................39

LCD Drivers .....................................................................................................................................41

Battery Monitor ................................................................................................................................41

EEPROM Interface .......................................................................................................................... 41

Hardware Watchdog Timer..............................................................................................................45

Program Security.............................................................................................................................45

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

Test Ports ........................................................................................................................................46

FUNCTIONAL DESCRIPTION.....................................................................................................................................47

Theory of Operation .......................................................................................................................................47

System Timing Summary...............................................................................................................................48

Battery Modes................................................................................................................................................49

BROWNOUT Mode .........................................................................................................................50

LCD Mode .......................................................................................................................................51

SLEEP Mode ...................................................................................................................................51

Fault and Reset Behavior ..............................................................................................................................56

Wake Up Behavior .........................................................................................................................................57

Wake on PB.....................................................................................................................................57

Wake on Timer ................................................................................................................................57

Data Flow.......................................................................................................................................................58

CE/MPU Communication ...............................................................................................................................58

Temperature Measurement ...........................................................................................................................59

Temperature Compensation ..........................................................................................................................59

APPLICATION INFORMATION ...................................................................................................................................60

Connection of Sensors (CT, Resistive Shunt)................................................................................................60

Connecting 5V Devices..................................................................................................................................60

Connecting LCDs...........................................................................................................................................61

Connecting I2C EEPROMs ............................................................................................................................63

Connecting Three-Wire EEPROMs................................................................................................................63

UART0 (TX/RX) .............................................................................................................................................64

Optical Interface.............................................................................................................................................64

Connecting V1 and Reset Pins ......................................................................................................................65

Connecting the Emulator Port Pins ................................................................................................................66

Crystal Oscillator............................................................................................................................................ 67

Flash Programming........................................................................................................................................67

MPU Firmware Library ...................................................................................................................................67

Meter Calibration............................................................................................................................................67

FIRMWARE INTERFACE ............................................................................................................................................68

I/O RAM MAP – In Numerical Order ..............................................................................................................68

SFR MAP (SFRs Specific to TERIDIAN 80515) – In Numerical Order ..........................................................69

I/O RAM DESCRIPTION – Alphabetical Order ..............................................................................................70

CE Interface Description ................................................................................................................................76

CE Program.....................................................................................................................................76

Formats ...........................................................................................................................................76

Constants ........................................................................................................................................76

Environment ....................................................................................................................................76

CE Calculations ...............................................................................................................................77

CE STATUS ....................................................................................................................................77

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

CE TRANSFER VARIABLES ..........................................................................................................79

Other CE Parameters ......................................................................................................................80

ELECTRICAL SPECIFICATIONS ................................................................................................................................83

ABSOLUTE MAXIMUM RATINGS ................................................................................................................83

RECOMMENDED EXTERNAL COMPONENTS ...........................................................................................84

RECOMMENDED OPERATING CONDITIONS ............................................................................................84

PERFORMANCE SPECIFICATIONS ............................................................................................................85

INPUT LOGIC LEVELS ...................................................................................................................85

OUTPUT LOGIC LEVELS ...............................................................................................................85

POWER-FAULT COMPARATOR....................................................................................................85

BATTERY MONITOR ......................................................................................................................85

SUPPLY CURRENT........................................................................................................................86

V3P3D SWITCH .............................................................................................................................. 86

2.5V VOLTAGE REGULATOR ........................................................................................................86

LOW POWER VOLTAGE REGULATOR.........................................................................................87

CRYSTAL OSCILLATOR ................................................................................................................87

VREF, VBIAS ..................................................................................................................................87

ADC CONVERTER, V3P3A REFERENCED...................................................................................88

OPTICAL INTERFACE....................................................................................................................88

TEMPERATURE SENSOR .............................................................................................................89

LSB values do not include the 9-bit left shift at CE input. ................................................................89

LCD DRIVERS ................................................................................................................................88

TIMING SPECIFICATIONS ...........................................................................................................................90

RAM AND FLASH MEMORY ..........................................................................................................90

FLASH MEMORY TIMING ..............................................................................................................90

EEPROM INTERFACE....................................................................................................................90

RESET ............................................................................................................................................90

TYPICAL PERFORMANCE DATA ..................................................................................................91

PACKAGE OUTLINE (LQFP 64) ...................................................................................................................92

PINOUT (LQFP-64) .......................................................................................................................................93

PIN DESCRIPTIONS .....................................................................................................................................94

Power/Ground Pins:.........................................................................................................................94

Analog Pins: ....................................................................................................................................94

Digital Pins:......................................................................................................................................95

I/O Equivalent Circuits: ....................................................................................................................96

ORDERING INFORMATION .........................................................................................................................97

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

List of Figures

Figure 1: IC Functional Block Diagram...........................................................................................................................8

Figure 2: General Topology of a Chopped Amplifier .................................................................................................... 11

Figure 3: AFE Block Diagram.......................................................................................................................................12

Figure 4: Samples from Multiplexer Cycle....................................................................................................................14

Figure 5: Accumulation Interval....................................................................................................................................15

Figure 6: Interrupt Structure .........................................................................................................................................36

Figure 7: Optical Interface............................................................................................................................................ 39

Figure 8: Connecting an External Load to DIO Pins.....................................................................................................40

Figure 9: 3-Wire Interface. Write Command, HiZ=0. ....................................................................................................43

Figure 10: 3-Wire Interface. Write Command, HiZ=1 ...................................................................................................43

Figure 11: 3-Wire Interface. Read Command............................................................................................................... 44

Figure 12: 3-Wire Interface. Write Command when CNT=0.........................................................................................44

Figure 13: 3-Wire Interface. Write Command when HiZ=1 and WFR=1....................................................................... 44

Figure 14: Functions defined by V1..............................................................................................................................45

Figure 15: Voltage. Current, Momentary and Accumulated Energy .............................................................................47

Figure 16: Timing Relationship between ADC MUX, Compute Engine, and Serial Transfers. .....................................48

Figure 17: RTM Output Format ....................................................................................................................................49

Figure 18: Operation Modes State Diagram.................................................................................................................50

Figure 19: Functional Blocks in BROWNOUT Mode (inactive blocks grayed out)........................................................52

Figure 20: Functional Blocks in LCD Mode (inactive blocks grayed out)......................................................................53

Figure 21: Functional Blocks in SLEEP Mode (inactive blocks grayed out) .................................................................54

Figure 22: Transition from BROWNOUT to MISSION Mode when System Power Returns .........................................55

Figure 23: Power-Up Timing with V3P3SYS and VBAT tied together .......................................................................... 55

Figure 24: Power-Up Timing with VBAT only ...............................................................................................................56

Figure 25: Wake Up Timing..........................................................................................................................................57

Figure 26: MPU/CE Data Flow .....................................................................................................................................58

Figure 27: MPU/CE Communication ............................................................................................................................58

Figure 28: Resistive Voltage Divider (Left), Current Transformer (Right) .....................................................................60

Figure 29: Resistive Shunt ...........................................................................................................................................60

Figure 30: Connecting LCDs ........................................................................................................................................61

Figure 31: I2C EEPROM Connection............................................................................................................................63

Figure 32: Three-Wire EEPROM Connection...............................................................................................................63

Figure 33: Connections for the RX Pin.........................................................................................................................64

Figure 34: Connection for Optical Components ...........................................................................................................65

Figure 35: Voltage Divider for V1 .................................................................................................................................65

Figure 36: External Components for the RESET Pin: Push-Button (Left), EMI Circuit (Right) .....................................66

Figure 37: External Components for the Emulator Interface ........................................................................................66

Figure 38: Wh Accuracy, 0.1A to 200A at 240V/50Hz and Room Temperature...........................................................91

Figure 39: Meter Accuracy over Harmonics at 240V, 30A............................................................................................91

Figure 40: Typical Meter Accuracy over Temperature Relative to 25°C.......................................................................92

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

List of Tables

Table 1: Inputs Selected in Regular and Alternate Multiplexer Cycles ...........................................................................9

Table 2: CE DRAM Locations for ADC Results............................................................................................................13

Table 3: Memory Map ..........................................................................................................................................16

Table 4: Stretch Memory Cycle Width..........................................................................................................................17

Table 5: Internal Data Memory Map............................................................................................................................. 18

Table 6: Special Function Registers Locations ............................................................................................................18

Table 7: Special Function Registers Reset Values ......................................................................................................19

Table 8: PSW Register Flags .......................................................................................................................................20

Table 9: PSW Bit Functions .........................................................................................................................................20

Table 10: Port Registers ..........................................................................................................................................21

Table 11: Special Function Registers...........................................................................................................................22

Table 12: Baud Rate Generation..................................................................................................................................23

Table 13: UART Modes ..........................................................................................................................................23

Table 14: The S0CON Register ...................................................................................................................................23

Table 15: The S1CON register.....................................................................................................................................23

Table 16: The S0CON Bit Functions ............................................................................................................................24

Table 17: The S1CON Bit Functions ............................................................................................................................24

Table 18: The TCON Register......................................................................................................................................25

Table 19: The TCON Register Bit Functions ................................................................................................................25

Table 20: The TMOD Register .....................................................................................................................................26

Table 21: TMOD Register Bit Description ....................................................................................................................26

Table 22: Timers/Counters Mode Description ..............................................................................................................26

Table 23: Timer Modes ..........................................................................................................................................27

Table 24: The PCON Register .....................................................................................................................................27

Table 25: PCON Register Bit Description.....................................................................................................................27

Table 26: The IEN0 Register (see also Table 32) ........................................................................................................28

Table 27: The IEN0 Bit Functions (see also Table 32).................................................................................................28

Table 28: The IEN1 Register (see also Tables 30/31) .................................................................................................28

Table 29: The IEN1 Bit Functions (see also Tables 31/32) ..........................................................................................28

Table 30: The IP0 Register (see also Table 45)........................................................................................................... 29

Table 31: The IP0 bit Functions (see also Table 45).................................................................................................... 29

Table 32: The WDTREL Register.................................................................................................................................29

Table 33: The WDTREL Bit Functions .........................................................................................................................29

Table 34: The IEN0 Register........................................................................................................................................30

Table 35: The IEN0 Bit Functions ................................................................................................................................30

Table 36: The IEN1 Register........................................................................................................................................30

Table 37: The IEN1 Bit Functions ................................................................................................................................31

Table 38: The IEN2 Register........................................................................................................................................31

Table 39: The IEN2 Bit Functions ................................................................................................................................31

Table 40: The TCON Register......................................................................................................................................31

Table 41: The TCON Bit Functions ..............................................................................................................................31

Table 42: The T2CON Bit Functions ............................................................................................................................32

Table 43: The IRCON Register ....................................................................................................................................32

Table 44: The IRCON Bit Functions.............................................................................................................................32

Table 45: External MPU Interrupts ...............................................................................................................................33

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

Table 46: Interrupt Enable and Flag Bits.....................................................................................................................33

Table 47: Priority Level Groups....................................................................................................................................34

Table 48: The IP0 Register 34

Table 49: The IP1 Register: .........................................................................................................................................34

Table 50: Priority Levels ..........................................................................................................................................35

Table 51: Interrupt Polling Sequence ...........................................................................................................................35

Table 52: Interrupt Vectors ..........................................................................................................................................35

Table 53: Data/Direction Registers and Internal Resources for DIO Pin Groups .........................................................39

Table 54: DIO_DIR Control Bit .....................................................................................................................................40

Table 55: Selectable Controls using the DIO_DIR Bits ................................................................................................41

Table 56: EECTRL Status Bits.....................................................................................................................................42

Table 57: EECTRL bits for 3-wire interface.................................................................................................................43

Table 58: TMUX[4:0] Selections...................................................................................................................................46

Table 59: Available Circuit Functions (“—“ means “not active)..................................................................................... 51

Table 60: LCD and DIO Pin Assignment by LCD_NUM...............................................................................................62

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

MUX

XIN

XOUT

VREF

CKADC

CKTEST/

SEG19

32 bit Compute

Engine

MPU

(80515)

CONTROL

OPT_RX/

DIO1

OPT_TX/

DIO2/

WPULSE/

VARPULSE

RESET

VBIAS

EMULATOR

PORT

CE_BUSY

OPTICAL

UART

XFER BUSY

COM0..3

VLC2

LCD DISPLAY

DRIVER

DATA

00-7F

PROG

000-1FF

DATA

0000-FFFF

PROG

0000-1FFF

0000-

1FFF

MPU XRAM

(2KB)

0000-07FF

DIGITAL I/O

CONFIG

(I/O RAM)

2000-20FF

I/O RAM

CE RAM

(0.5KB)

MEMORY SHARE

1000-11FF

32KHz

MUX_SYNC

CKCE

CKMPU

CK32

CE_E

RTM_E

COMP_STAT

POWER FAULT

LCD_E

LCD_CLK

LCD_MODE

DIO

4.9MH z

<4.9MHz

4.9MHz

GNDD

V3P3A

V3P3D

VBAT

VOLT

REG

2.5V to logic

V2P5

MPU_DIV

SUM_CYCLES

PRE_SAMPS

EQU

CKOUT_E

32KHz

TMUXOUT

MPU_RSTZ

FAULTZ

WAKE

TMUX[4:0]

CONFIGURATION

PARAMETERS

GNDA

VBIAS

TEMP

February 2, 2007

CROSS

CK_GEN

OSC

(32KHz)

CK32

CKOUT_E

MCK

PLL

VREF

VREF_DI S

DIV

ADC

MUX

CTRL

MUX_DIV

CHOP_E

EQU

STRT

MUX

CKFIR

4.9MHz

RTM

SEG34/DIO14 ..

SEG37/DIO17

WPULSE

VARPULSE

WPULSE

VARPULSE

TEST

MODE

LCD_MODE

VLC1

VLC0

LCD_E

<4.9MHz

LCD_NU M

DIO_R

DIO_DIR

LCD_NU M

DIO_PV/PW

MUX_ALT

SEG24/DIO4 ..

SEG31/DIO11

SDCK

SDOUT

SDIN

E_RXTX/SEG38

E_TCLK/SEG33

E_RST/SEG32

FLASH

8KB

FLSH66ZT

V3P3A

FIR_LEN

FIR

SEG0..18

EEPROM

INTERFACE

DIO_EEX

CK_2X

ECK_DIS

OPT_TXE

V3P3D

LCD_GEN

X4MHZ

VBIAS

MEMORY

SEG32,33

SEG19,38

E_RXTX

E_TCLK

E_RST (Open Drain)

ICE_E

DIO1,2

VREF_CAL

ΔΣ ADC

CONVERTER

VREF

ADC_E

RTM_0..3

CE_LCTN

PLS_MAXWIDTH

PLS_INTERVAL

PLS_INV

OPT_TXINV

OPT_TXMOD

OPT_FDC

OPT_RXINV

OPT_RXDIS

LCD_BLKMAP

LCD_SEG

LCD_ Y

SLEEP

LCD_ONLY

V3P3SYS

TEST

MUX

CE_LCTN

Figure 1: IC Functional Block Diagram

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

HARDWARE DESCRIPTION

Hardware Overview

The TERIDIAN 71M6521BE single-chip energy meter integrates all primary functional blocks required to implement a solid-

state electricity meter. Included on chip are an analog front end (AFE), an independent digital computation engine (CE), an

8051-compatible microprocessor (MPU) which executes one instruction per clock cycle (80515), a voltage reference, a

temperature sensor, LCD drivers, RAM, Flash memory, and a variety of I/O pins. Various current sensor technologies are

supported including Current Transformers (CT) and Resistive Shunts.

In a typical application, the 32-bit compute engine (CE) of the 71M6521BE sequentially processes the samples from the

voltage inputs on pins IA, VA, IB, VB1 and performs calculations to measure active energy (Wh). This measurement is then

accessed by the MPU, processed further and output using the peripheral devices available to the MPU.

Measurements can be displayed on 3.3V LCD commonly used in low temperature environments. Flexible mapping of LCD

display segments will facilitate integration of existing custom LCD. Design trade-off between the number of LCD segments vs.

DIO pins can be implemented in software to accommodate various requirements.

The on-chip digital temperature compensation mechanism includes a temperature sensor and associated controls for

correction of unwanted temperature effects on measurement. Temperature dependent external components such as crystal

oscillator, current sensors, and their corresponding signal conditioning circuits can be characterized and their correction factors

can be programmed to produce electricity meters with exceptional accuracy over the industrial temperature range.

One of the two internal UARTs is adapted to support an Infrared LED with internal drive and sense configuration, and can also

function as a standard UART. The optical output can be modulated at 38kHz. This flexibility makes it possible to implement

AMR meters with an IR interface. A block diagram of the IC is shown in Figure 1. A detailed description of various functional

blocks follows.

Analog Front End (AFE)

The AFE of the 71M6521BE is comprised of an input multiplexer, a delta-sigma A/D converter and a voltage reference.

Input Multiplexer

The input multiplexer supports up to four input signals that are applied to pins IA, VA, IB and VB1 of the device. Additionally,

using the alternate multiplexer selection, it has the ability to select temperature and the battery voltage. The multiplexer can be

operated in two modes:

• During a normal multiplexer cycle, the signals from the IA, IB, VA, and VB pins are selected.

• During the alternate (ALT) multiplexer cycle, the temperature signal (TEMP) and the battery monitor are selected,

along with the signal sources shown in Table 1. To prevent unnecessary drainage on the battery, the battery monitor

is enabled only with the BME bit (0x2020[6]) in the I/O RAM.

The alternate multiplexer cycles are usually performed infrequently (e. g. every second or so) by the MPU. In order to prevent

disruption of the voltage tracking PLL and voltage allpass networks, VA is not replaced in the ALT multiplexer selections.

Missing samples due to an ALT multiplexer sequence are filled in by the CE.

Regular MUX Sequence ALT MUX Sequence

Mux State Mux State

EQU 0 1 2 3 0 1 2 3

0 IA VA IB VB TEMP VA IB VBAT

Table 1: Inputs Selected in Regular and Alternate Multiplexer Cycles

1: VB is available, but not used in typical 1-phase, 2-wire meters

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

In a typical application, IA and IB are connected to current transformers that sense the current on each phase of the line

voltage. VA is typically connected to a voltage sensor (resistor divider).

The multiplexer control circuit handles the setting of the multiplexer. The function of the multiplexer control circuit is governed

by the I/O RAM registers MUX_ALT, MUX_DIV and EQU. MUX_DIV controls the number of samples per cycle. It can request 2,

3, or 4 multiplexer states per cycle. Multiplexer states above 4 are reserved and must not be used. The multiplexer always

starts at the beginning of its list and proceeds until MUX_DIV states have been converted.

The MUX_ALT bit requests an alternative multiplexer frame. The bit may be asserted on any MPU cycle and may be

subsequently de-asserted on any cycle including the next one. A rising edge on MUX_ALT will cause the multiplexer control

circuit to wait until the next multiplexer cycle and implement a single alternate cycle.

The multiplexer control circuit also controls the FIR filter initiation and the chopping of the ADC reference voltage, VREF. The

multiplexer control circuits clocked by CK32, the 32768Hz clock from the PLL block, and launches each pass through the CE

program.

A/D Converter (ADC)

A single delta-sigma A/D converter digitizes the voltage and current inputs to the 71M6521BE. The resolution of the ADC is

programmable using the FIR_LEN register as shown in the I/O RAM section. ADC resolution can be selected to be 21 bits

(FIR_LEN=0), or 22 bits (FIR_LEN=1). Conversion time is two cycles of CK32 with FIR_LEN = 0 and three cycles with FIR_LEN

= 1.

In order to provide the maximum resolution, the ADC should be operated with FIR_LEN = 1. Accuracy and timing

specifications in this data sheet are based on FIR_LEN = 1.

Initiation of each ADC conversion is controlled by the multiplexer control circuit as described previously. At the end of each

ADC conversion, the FIR filter output data is stored into the CE DRAM location determined by the multiplexer selection.

FIR Filter

The finite impulse response filter is an integral part of the ADC and it is optimized for use with the multiplexer. The purpose of

the FIR filter is to decimate the ADC output to the desired resolution. At the end of each ADC conversion, the output data is

stored into the fixed CE DRAM location determined by the multiplexer selection. FIR data is stored LSB justified, but shifted left

by nine bits.

Voltage References

The device includes an on-chip precision bandgap voltage reference that incorporates auto-zero techniques. The reference is

trimmed to minimize errors caused by component mismatch and drift. The result is a voltage output with a predictable

temperature coefficient.

The amplifier within the reference is chopper stabilized, i.e. the polarity can be switched by the MPU using the I/O RAM

register CHOP_E (0x2002[5:4]). The two bits in the CHOP_E register enable the MPU to operate the chopper circuit in regular

or inverted operation, or in “toggling” mode. When the chopper circuit is toggled in between multiplexer cycles, DC offsets on

the measured signals will automatically be averaged out.

The general topology of a chopped amplifier is given in Figure 2.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

inp

outp

outn

inn

CROSS

Figure 2: General Topology of a Chopped Amplifier

It is assumed that an offset voltage Voff appears at the positive amplifier input. With all switches, as controlled by CROSS in

the “A” position, the output voltage is:

Voutp – Voutn = G (Vinp + Voff – Vinn) = G (Vinp – Vinn) + G Voff

With all switches set to the “B” position by applying the inverted CROSS signal, the output voltage is:

Voutn – Voutp = G (Vinn – Vinp + Voff) = G (Vinn – Vinp) + G Voff, or

Voutp – Voutn = G (Vinp – Vinn) - G Voff

Thus, when CROSS is toggled, e.g. after each multiplexer cycle, the offset will alternately appear on the output as positive and

negative, which results in the offset effectively being eliminated, regardless of its polarity or magnitude.

When CROSS is high, the hookup of the amplifier input devices is reversed. This preserves the overall polarity of that

amplifier gain, it inverts its input offset. By alternately reversing the connection, the amplifier’s offset is averaged to zero. This

removes the most significant long-term drift mechanism in the voltage reference. The CHOP_E bits control the behavior of

CROSS. The CROSS signal will reverse the amplifier connection in the voltage reference in order to negate the effects of its

offset. On the first CK32 rising edge after the last mux state of its sequence, the mux will wait one additional CK32 cycle

before beginning a new frame. At the beginning of this cycle, the value of CROSS will be updated according to the CHOP_E

bits. The extra CK32 cycle allows time for the chopped VREF to settle. During this cycle, MUXSYNC is held high. The

leading edge of muxsync initiates a pass through the CE program sequence. The beginning of the sequence is the serial

readout of the 4 RTM words.

CHOP_E has 3 states: positive, reverse, and chop. In the ‘positive’ state, CROSS is held low. In the ‘reverse’ state, CROSS is

held high. In the ‘chop’ state, CROSS is toggled near the end of each Mux Frame, as described above. It is desirable that

CROSS take on alternate values at the beginning of each Mux cycle. For this reason, if ‘chop’ state is selected, CROSS will

not toggle at the end of the last Mux cycle in a SUM cycle.

The internal bias voltage VBIAS (typically 1.6V) is used by the ADC when measuring the temperature and battery monitor

signals.

Temperature Sensor

The 71M6521BE includes an on-chip temperature sensor implemented as a bandgap reference. It is used to determine the die

temperature The MPU may request an alternate multiplexer cycle containing the temperature sensor output by asserting

MUX_ALT.

The primary use of the temperature data is to determine the magnitude of compensation required to offset the thermal drift in

the system (see section titled “Temperature Compensation”).

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Battery Monitor

The battery voltage is measured by the ADC during alternative multiplexer frames if the BME (Battery Measure Enable) bit in

the I/O RAM is set. While BME is set, an on-chip 45kΩ load resistor is applied to the battery, and a scaled fraction of the

battery voltage is applied to the ADC input. After each alternative MUX frame, the result of the ADC conversion is available at

CE DRAM address 07. BME is ignored and assumed zero when system power is not available (V1 < VBIAS). See the Battery

Monitor section of the Electrical Specifications for details regarding the ADC LSB size and the conversion accuracy.

Functional Description

The AFE functions as a data acquisition system, controlled by the MPU. The main signals (IA, VA, IB, VB) are sampled and

the ADC counts obtained are stored in CE DRAM where they can be accessed by the CE and, if necessary, by the MPU.

Alternate multiplexer cycles are initiated less frequently by the MPU to gather access to the slow temperature and battery

signals.

MUX

VREF

4.9MHz

VBIAS

CROSS

CK32

VREF

VREF_DIS

MUX

CTRL

MUX_DIV

CHOP_E

EQU

MUX

MUX_ALT

V3P3A

FIR_LEN

FIR

VBIAS

VREF_ CAL

ΔΣ ADC

CONVERTER

VREF

ADC_E

TEMP

VBAT

FIR_DONE

FIR_START

Figure 3: AFE Block Diagram

Digital Computation Engine (CE)

The CE, a dedicated 32-bit signal processor, performs the precision computations necessary to accurately measure energy.

The CE calculations and processes include:

• Multiplication of each current sample with its associated voltage sample to obtain the energy per sample (when

multiplied with the constant sample time).

• Frequency-insensitive delay cancellation on all channels (to compensate for the delay between samples caused by

the multiplexing scheme).

• Pulse generation.

• Monitoring of the input signal frequency (for frequency and phase information).

• Monitoring of the input signal amplitude (for sag detection).

• Scaling of the processed samples based on calibration coefficients.

The CE program resides in flash memory. Common access to flash memory by CE and MPU is controlled by a memory share

circuit. Each CE instruction word is two bytes long. Allocated flash space for the CE program cannot exceed 1024 words

(2KB). The CE program counter begins a pass through the CE code each time multiplexer state 0 begins. The code pass ends

when a HALT instruction is executed. For proper operation, the code pass must be completed before the multiplexer cycle

ends (see System Timing Summary in the Functional Description Section).

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The CE program must begin on a 1Kbyte boundary of the flash address. The I/O RAM register CE_LCTN[4:0] defines which

1KB boundary contains the CE code. Thus, the first CE instruction is located at 1024*CE_LCTN[4:0].

The CE DRAM can be accessed by the FIR filter block, the RTM circuit, the CE, and the MPU. Assigned time slots are re-

served for FIR, RTM, and MPU, respectively, to prevent bus contention for CE DRAM data access. Holding registers are used

to convert 8-bit wide MPU data to/from 32-bit wide CE DRAM data, and wait states are inserted as needed, depending on the

frequency of CKMPU.

The CE DRAM is 128 32-bit words. The MPU can read and write the CE DRAM as the primary means of data communication

between the two processors.

Table 2 shows the CE DRAM addresses allocated to analog inputs from the AFE.

Address (HEX) Name Description

00 IA Phase A current

01 VA Phase A voltage

02 IB Phase B current

03 VB (Phase B voltage – not used)

04 - Not used

05 - Not used

06 TEMP Temperature

07 VBAT Battery Voltage

Table 2: CE DRAM Locations for ADC Results

The CE of the 71M6521BE is aided by support hardware that facilitates implementation of equations, pulse counters, and

accumulators. This support hardware is controlled through I/O RAM locations EQU (equation assist), DIO_PV and DIO_PW

(pulse count assist), and PRE_SAMPS and SUM_CYCLES (accumulation assist). PRE_SAMPS and SUM_CYCLES support a dual

level accumulation scheme where the first accumulator accumulates results from PRE_SAMPS samples and the second accu-

mulator accumulates up to SUM_CYCLES of the first accumulator results. The integration time for each energy output is

PRE_SAMPS * SUM_CYCLES/2520.6 (with MUX_DIV = 1). CE hardware issues the XFER_BUSY interrupt when the

accumulation is complete.

Meter Equations

Compute Engine (CE) firmware for residential meter configurations implements the calculations for equation 0 for a single-

element, 2-wire, 1-phase meter with neutral current sense and tamper detection. The energy for element 0 is determined by

VA*IA, and the energy for element 1 is determined by VA*IB.

Real-Time Monitor

The CE contains a Real-Time Monitor (RTM), which can be programmed through the UART to monitor four selectable CE

DRAM locations at full sample rate. The four monitored locations are serially output to the TMUXOUT pin via the digital output

multiplexer at the beginning of each CE code pass. The RTM can be enabled and disabled with RTM_EN. The RTM output is

clocked by CKTEST. Each RTM word is clocked out in 35 cycles and contains a leading flag bit. See the Functional

Description section for the RTM output format. RTM is low when not in use.

Pulse Generator

The chip contains a pulse generator that creates low-jitter Wh pulses at a rate set by the CE.

The I/O RAM bit DIO_PW, as described in the Digital I/O section, can be programmed to route WPULSE to the output pin

DIO6. Pulses can also be output on OPT_TX (see OPT_TXE[1:0] for details).

The value of PLS_INTERVAL depends on the sample rate (nominal 2520Hz) and the number of times the pulse generator is

executed in the CE code. Changing these values would require redesign of all CE filters and/or modification of the CE pulse

generator code. Since these numbers are fixed for the CE code supplied by TERIDIAN, the value of PLS_INTERVAL is also

fixed, to a value of 0x81.

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On-chip hardware provides a maximum pulse width feature: PLS_MAXWIDTH[7:0] selects a maximum negative pulse width to

be ‘Nmax’ updates according to the formula: Nmax = (2*PLS_MAXWIDTH+1). If PLS_MAXWIDTH = 255, no width checking is

performed.

Given that PLS_INTERVAL = 81, the maximum pulse width is determined by:

Maximum Pulse Width = (2 * PLS_MAXWIDTH +1) * 81*4*203ns = 65.8µs + PLS_MAXWIDTH * 131.5µs

The CE pulse output polarity is programmable to be either positive or negative. Pulse polarity may be inverted with PLS_INV.

When this bit is set, the pulses are active high, rather than the more usual active low.

CE Functional Overview

The ADC processes one sample per channel per multiplexer cycle. Figure 4 shows the timing of the samples taken during one

multiplexer cycle.

The number of samples processed during one accumulation cycle is controlled by the I/O RAM registers PRE_SAMPS

(0x2001[7:6]) and SUM_CYCLES (0x2001[5:0]). The integration time for each energy output is

PRE_SAMPS * SUM_CYCLES / 2520.6, where 2520.6 is the sample rate [Hz]

For example, PRE_SAMPS = 42 and SUM_CYCLES = 50 will establish 2100 samples per accumulation cycle. PRE_SAMPS = 100

and SUM_CYCLES = 21 will result in the exact same accumulation cycle of 2100 samples or 833ms. After an accumulation

cycle is completed, the XFER_BUSY interrupt signals to the MPU that accumulated data are available.

1/32768Hz =

30.518µs

13/32768Hz = 397µs

per mux cycle

Figure 4: Samples from Multiplexer Cycle

The end of each multiplexer cycle is signaled to the MPU by the CE_BUSY interrupt. At the end of each multiplexer cycle,

status information, such as sag data and the digitized input signal, is available to the MPU.

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XFER_BUSY

Interrupt to MPU

20ms

833ms

Figure 5: Accumulation Interval

Figure 5 shows the accumulation interval resulting from PRE_SAMPS = 42 and SUM_CYCLES = 50, consisting of 2100 samples

of 397µs each, followed by the XFER_BUSY interrupt. The sampling in this example is applied to a 50Hz signal.

There is no correlation between the line signal frequency and the choice of PRE_SAMPS or SUM_CYCLES (even though when

SUM_CYCLES = 42 one set of SUM_CYCLES happens to sample a period of 16.6ms). Furthermore, sampling does not have to

start when the line voltage crosses the zero line, and the length of the accumulation interval need not be an integer multiple of

the signal cycles.

It is important to note that the length of the accumulation interval, as determined by NACC, the product of SUM_CYCLES and

PRE_SAMPS, is not an exact multiple of 1000ms. For example, if SUM_CYCLES = 60, and PRE_SAMPS = 00 (42), the

resulting accumulation interval is:

ACC 75.999

62.2520

2520

32768

4260 ==

⋅

This means that accurate time measurements should be not be based on the accumulation interval without correction.

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80515 MPU Core

The 71M6521BE includes an 80515 MPU (8-bit, 8051-compatible) that processes most instructions in one clock cycle. Using a

5MHz clock results in a processing throughput of 5 MIPS. The 80515 architecture eliminates redundant bus states and im-

plements parallel execution of fetch and execution phases. Normally a machine cycle is aligned with a memory fetch, there-

fore, most of the 1-byte instructions are performed in a single cycle. This leads to an 8x performance (in average) improvement

(in terms of MIPS) over the Intel 8051 device running at the same clock frequency.

Actual processor clocking speed can be adjusted to the total processing demand of the application (metering calculations,

AMR management, memory management, LCD driver management and I/O management) using the I/O RAM register

MPU_DIV[2:0].

Typical measurement and metering functions based on the results provided by the internal 32-bit compute engine (CE) are

available for the MPU as part of TERIDIAN’s standard library. A standard ANSI “C” 80515-application programming interface

library is available to help reduce design cycle.

Memory Organization

The 80515 MPU core incorporates the Harvard architecture with separate code and data spaces.

Memory organization in the 80515 is similar to that of the industry standard 8051. There are three memory areas: Program

memory (Flash), external data memory (XRAM), physically consisting of XRAM, CE DRAM, and I/O RAM, and internal data

memory (Internal RAM). Table 3 shows the memory map.

Address

(hex)

Memory

Technology Memory Type Typical Usage Wait States

(at 5MHz)

Memory Size

(bytes)

0000-1FFF Flash Memory Non-volatile MPU Program and non-

volatile data 0 8K

on 1K

boundary Flash Memory Non-volatile CE program 0 2K

0000-07FF Static RAM Volatile MPU data XRAM, 0 2K

1000-11FF Static RAM Volatile CE data 6 512

2000-20FF Static RAM Volatile Configuration RAM

I/O RAM 0 256

Table 3: Memory Map

Internal and External Data Memory: Both internal and external data memory are physically located on the 71M6521BE IC.

“External” data memory is only external to the 80515 MPU core.

Program Memory: The 80515 can theoretically address up to 64KB of program memory space from 0x0000 to 0xFFFF.

Program memory is read when the MPU fetches instructions or performs a MOVC operation.

After reset, the MPU starts program execution from location 0x0000. The lower part of the program memory includes reset and

interrupt vectors. The interrupt vectors are spaced at 8-byte intervals, starting from 0x0003.

External Data Memory: While the 80515 is capable of addressing up to 64KB of external data memory in the space from

0x0000 to 0xFFFF, only the memory ranges shown in Error! Reference source not found. contain physical memory. The

80515 writes into external data memory when the MPU executes a MOVX @Ri,A or MOVX @DPTR,A instruction. The MPU

reads external data memory by executing a MOVX A,@Ri or MOVX A,@DPTR instruction (SFR USR2 provides the upper 8

bytes for the MOVX A,@Ri instruction).

Clock Stretching: MOVX instructions can access fast or slow external RAM and external peripherals. The three low order bits

of the CKCON register define the stretch memory cycles. Setting all the CKCON stretch bits to one allows access to very slow

external RAM or external peripherals.

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Table 4 shows how the signals of the External Memory Interface change when stretch values are set from 0 to 7. The widths of

the signals are counted in MPU clock cycles. The post-reset state of the CKCON register, which is in bold in the table, performs

the MOVX instructions with a stretch value equal to 1.

CKCON register Read signals width Write signal width

CKCON.2 CKCON.1 CKCON.0

Stretch Value

memaddr memrd memaddr memwr

0 0 0 0 1 1 2 1

0 0 1 1 2 2 3 1

0 1 0 2 3 3 4 2

0 1 1 3 4 4 5 3

1 0 0 4 5 5 6 4

1 0 1 5 6 6 7 5

1 1 0 6 7 7 8 6

1 1 1 7 8 8 9 7

Table 4: Stretch Memory Cycle Width

There are two types of instructions, differing in whether they provide an eight-bit or sixteen-bit indirect address to the external

data RAM.

In the first type (MOVX A,@Ri), the contents of R0 or R1, in the current register bank, provide the eight lower-ordered bits of

address. The eight high-ordered bits of address are specified with the USR2 SFR. This method allows the user paged access

(256 pages of 256 bytes each) to all ranges of the external data RAM. In the second type of MOVX instruction (MOVX

A,@DPTR), the data pointer generates a sixteen-bit address. This form is faster and more efficient when accessing very large

data arrays (up to 64 Kbytes), since no additional instructions are needed to set up the eight high ordered bits of address.

It is possible to mix the two MOVX types. This provides the user with four separate data pointers, two with direct access and

two with paged access to the entire 64KB of external memory range.

Dual Data Pointer: The Dual Data Pointer accelerates the block moves of data. The standard DPTR is a 16-bit register that is

used to address external memory or peripherals. In the 80515 core, the standard data pointer is called DPTR, the second data

pointer is called DPTR1. The data pointer select bit chooses the active pointer. The data pointer select bit is located at the LSB

of the DPS register (DPS.0). DPTR is selected when DPS.0 = 0 and DPTR1 is selected when DPS.0 = 1.

The user switches between pointers by toggling the LSB of the DPS register. All DPTR-related instructions use the currently

selected data pointer for any activity.

The second data pointer may not be supported by certain compilers.

Internal Data Memory: The Internal data memory provides 256 bytes (0x00 to 0xFF) of data memory. The internal data

memory address is always one byte wide and can be accessed by either direct or indirect addressing. The Special Function

Registers occupy the upper 128 bytes. This SFR area is available only by direct addressing. Indirect addressing

accesses the upper 128 bytes of Internal RAM.

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Internal Data Memory: The lower 128 bytes contain working registers and bit-addressable memory. The lower 32 bytes form

four banks of eight registers (R0-R7). Two bits on the program memory status word (PSW) select which bank is in use. The

next 16 bytes form a block of bit-addressable memory space at bit addressees 0x00-0x7F. All of the bytes in the lower 128

bytes are accessible through direct or indirect addressing. Table 5 shows the internal data memory map.

Address Direct addressing Indirect addressing

0xFF

0x80

Special Function Registers

(SFRs) RAM

0x7F

0x30

Byte-addressable area

0x2F

0x20

Bit-addressable area

0x1F

0x00 Register banks R0…R7

Table 5: Internal Data Memory Map

Special Function Registers (SFRs)

A map of the Special Function Registers is shown in Table 6.

Bit-address-

able Byte-addressable

Hex\Bin

X000 X001 X010 X011 X100 X101 X110 X111

Bin/Hex

F8 INTBITS

F0 B

E8 WDI

E0 A

D8 WDCON

D0 PSW

C8 T2CON CF

C0 IRCON

B8 IEN1 IP1 S0RELH S1RELH USR2

B0 FLSHCTL PGADR B7

A8 IEN0 IP0 S0RELL

A0 P2 DIR2 DIR0

98 S0CON S0BUF IEN2 S1CON

S1BUF S1RELL

EEDATA EECTRL 9F

90 P1 DIR1 DPS

ERASE

88 TCON TMOD TL0 TL1

TH0 TH1

CKCON 8F

80 P0 SP DPL DPH

DPL1 DPH1

WDTREL PCON 87

Table 6: Special Function Registers Locations

Only a few addresses are occupied, the others are not implemented. SFRs specific to the 6521BE are shown in bold print. Any

read access to unimplemented addresses will return undefined data, while any write access will have no effect. The registers at

0x80, 0x88, 0x90, etc., are bit-addressable, all others are byte-addressable.

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Special Function Registers (Generic 80515 SFRs)

Table 7 shows the location of the SFRs and the value they assume at reset or power-up.

Name Location Reset Value Description

P0 0x80 0xFF Port 0

SP 0x81 0x07 Stack Pointer

DPL 0x82 0x00 Data Pointer Low 0

DPH 0x83 0x00 Data Pointer High 0

DPL1 0x84 0x00 Data Pointer Low 1

DPH1 0x85 0x00 Data Pointer High 1

WDTREL 0x86 0x00 Watchdog Timer Reload register

PCON 0x87 0x00 UART Speed Control

TCON 0x88 0x00 Timer/Counter Control

TMOD 0x89 0x00 Timer Mode Control

TL0 0x8A 0x00 Timer 0, low byte

TL1 0x8B 0x00 Timer 1, high byte

TH0 0x8C 0x00 Timer 0, low byte

TH1 0x8D 0x00 Timer 1, high byte

CKCON 0x8E 0x01 Clock Control (Stretch=1)

P1 0x90 0xFF Port 1

DPS 0x92 0x00 Data Pointer select Register

S0CON 0x98 0x00 Serial Port 0, Control Register

S0BUF 0x99 0x00 Serial Port 0, Data Buffer

IEN2 0x9A 0x00 Interrupt Enable Register 2

S1CON 0x9B 0x00 Serial Port 1, Control Register

S1BUF 0x9C 0x00 Serial Port 1, Data Buffer

S1RELL 0x9D 0x00 Serial Port 1, Reload Register, low byte

P2 0xA0 0x00 Port 2

IEN0 0xA8 0x00 Interrupt Enable Register 0

IP0 0xA9 0x00 Interrupt Priority Register 0

S0RELL 0xAA 0xD9 Serial Port 0, Reload Register, low byte

IEN1 0xB8 0x00 Interrupt Enable Register 1

IP1 0xB9 0x00 Interrupt Priority Register 1

S0RELH 0xBA 0x03 Serial Port 0, Reload Register, high byte

S1RELH 0xBB 0x03 Serial Port 1, Reload Register, high byte

USR2 0xBF 0x00 User 2 Port, high address byte for MOVX@Ri

IRCON 0xC0 0x00 Interrupt Request Control Register

T2CON 0xC8 0x00 Polarity for INT2 and INT3

PSW 0xD0 0x00 Program Status Word

WDCON 0xD8 0x00 Baud Rate Control Register (only WDCON.7 bit used)

A 0xE0 0x00 Accumulator

B 0xF0 0x00 B Register

Table 7: Special Function Registers Reset Values

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Accumulator (ACC, A): ACC is the accumulator register. Most instructions use the accumulator to hold the operand. The

mnemonics for accumulator-specific instructions refer to accumulator as “A”, not ACC.

B Register: The B register is used during multiply and divide instructions. It can also be used as a scratch-pad register to hold

temporary data.

Program Status Word (PSW):

MSB LSB

CV AC F0 RS1 RS OV - P

Table 8: PSW Register Flags

Bit Symbol Function

PSW.7 CV Carry flag

PSW.6 AC Auxiliary Carry flag for BCD operations

PSW.5 F0 General purpose Flag 0 available for user.

F0 is not to be confused with the F0 flag in the CE STATUS register.

PSW.4 RS1

PSW.3 RS0

RS1/RS0 Bank selected Location

00 Bank 0 (0x00 – 0x07)

01 Bank 1 (0x08 – 0x0F)

10 Bank 2 (0x10 – 0x17)

11 Bank 3 (0x18 – 0x1F)

PSW.2 OV Overflow flag

PSW.1 - User defined flag

PSW.0 P Parity flag, affected by hardware to indicate odd / even number of “one” bits in the

Accumulator, i.e. even parity.

Table 9: PSW Bit Functions

Stack Pointer (SP): The stack pointer is a 1-byte register initialized to 0x07 after reset. This register is incremented before

PUSH and CALL instructions, causing the stack to begin at location 0x08.

Data Pointer: The data pointer (DPTR) is 2 bytes wide. The lower part is DPL, and the highest is DPH. It can be loaded as two

registers (e.g. MOV DPL,#data8). It is generally used to access external code or data space (e.g. MOVC A,@A+DPTR or

MOVX A,@DPTR respectively).

Program Counter: The program counter (PC) is 2 bytes wide initialized to 0x0000 after reset. This register is incremented

when fetching operation code or when operating on data from program memory.

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Port Registers: The I/O ports are controlled by Special Function Registers P0, P1, and P2. The contents of the SFR can be

observed on corresponding pins on the chip. Writing a ‘1’ to any of the ports (see Table 10) causes the corresponding pin to be

at high level (V3P3), and writing a ‘0’ causes the corresponding pin to be held at low level (GND). The data direction registers

DIR0, DIR1, and DIR2 define individual pins as input or output pins (see section Digital I/O for details).

Address R/W Description

P0 0x80 R/W Register for port 0 read and write operations (pins DIO4…DIO7)

DIR0 0xA2 R/W Data direction register for port 0. Setting a bit to 1 means that the corresponding pin is

an output.

P1 0x90 R/W Register for port 1 read and write operations (pins DIO8…DIO11, DIO14…DIO15)

DIR1 0x91 R/W Data direction register for port 1.

P2 0xA0 R/W Register for port 2 read and write operations (pins DIO16…DIO17)

DIR2 0xA1 R/W Data direction register for port 2.

Table 10: Port Registers

All DIO ports on the chip are bi-directional. Each of them consists of a Latch (SFR ‘P0’ to ‘P2’), an output driver, and an input

buffer, therefore the MPU can output or read data through any of these ports. Even if a DIO pin is configured as an output, the

state of the pin can still be read by the MPU, for example when counting pulses issued via DIO pins that are under

CE control.

The technique of reading the status of or generating interrupts based on DIO pins configured as outputs, can be

used to implement pulse counting.

Special Function Registers Specific to the 71M6521BE

Table 11 shows the location and description of the 71M6521BE-specific SFRs.

Name

SFR

Address

R/W Description

ERASE FLSH_ERASE 0x94 W

This register is used to initiate either the Flash Mass Erase cycle or

the Flash Page Erase cycle. Specific patterns are expected for

FLSH_ERASE in order to initiate the appropriate Erase cycle (default =

0x00).

0x55 – Initiate Flash Page Erase cycle. Must be preceded by a write

to FLSH_PGADR @ SFR 0xB7.

0xAA – Initiate Flash Mass Erase cycle. Must be preceded by a write

to FLSH_MEEN @ SFR 0xB2 and the debug port must be

enabled.

Any other pattern written to FLSH_ERASE will have no effect.

PGADDR FLSH_PGADR 0xB7 R/W

Flash Page Erase Address register containing the flash memory page

address (page 0 thru 127) that will be erased during the Page Erase

cycle (default = 0x00).

Must be re-written for each new Page Erase cycle.

EEDATA 0x9E R/W I2C EEPROM interface data register

EECTRL 0x9F R/W

I2C EEPROM interface control register. If the MPU wishes to write a

byte of data to EEPROM, it places the data in EEDATA and then

writes the ‘Transmit’ code to EECTRL. The write to EECTRL initiates

the transmit sequence. See the EEPROM Interface section for a

description of the command and status bits available for EECTRL.

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FLSHCRL 0xB2

R/W

Bit 0 (FLSH_PWE): Program Write Enable:

0 – MOVX commands refer to XRAM Space, normal operation

(default).

1 – MOVX @DPTR,A moves A to Program Space (Flash) @

DPTR.

This bit is automatically reset after each byte written to flash. Writes

to this bit are inhibited when interrupts are enabled.

Bit 1 (FLSH_MEEN): Mass Erase Enable:

0 – Mass Erase disabled (default).

1 – Mass Erase enabled.

Must be re-written for each new Mass Erase cycle.

Bit 6 (SECURE):

Enables security provisions that prevent external reading of flash

memory and CE program RAM. This bit is reset on chip reset and

may only be set. Attempts to write zero are ignored.

Bit 7 (PREBOOT):

Indicates that the preboot sequence is active.

WDI 0xE8

R/W

Only byte operations on the whole WDI register

should be used when writing. The byte must have all

bits set except the bits that are to be cleared.

The multi-purpose register WDI contains the following bits:

Bit 0 (IE_XFER): XFER Interrupt Flag:

This flag monitors the XFER_BUSY interrupt. It is set by hardware

and must be cleared by the interrupt handler

Bit 1: Reserved

Bit 7 (WD_RST): WD Timer Reset:

Read: Reads the PLL_FALL interrupt flag

Write 0: Clears the PLL_FALL interrupt flag

Write 1: Resets the watch dog timer

INTBITS INT0…INT6 0xF8 R Interrupt inputs. The MPU may read these bits to see the input to

external interrupts INT0, INT1, up to INT6. These bits do not have

any memory and are primarily intended for debug use

Table 11: Special Function Registers

Instruction Set

All instructions of the generic 8051 microcontroller are supported. A complete list of the instruction set and of the associated

op-codes is contained in the 71M6521 Software User’s Guide (SUG).

UART

The 71M6521BE includes a UART (UART0) that can be programmed to communicate with a variety of AMR modules. A

second UART (UART1) is connected to the optical port, as described in the optical port description.

The UART is a dedicated 2-wire serial interface, which can communicate with an external host processor at up to 38,400 bits/s

((with MPU clock = 1.2288MHz). The operation of each pin is as follows:

RX: Serial input data are applied at this pin. Conforming to RS-232 standard, the bytes are input LSB first.

TX: This pin is used to output the serial data. The bytes are output LSB first.

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The 71M6521BE has several UART-related registers for the control and buffering of serial data. All UART transfers are pro-

grammable for parity enable, parity, 2 stop bits/1 stop bit and XON/XOFF options for variable communication baud rates from

300 to 38400 bps. Table 12 shows how the baud rates are calculated. Table 13 shows the selectable UART operation modes.

Using Timer 1 Using Internal Baud Rate Generator

UART0 2SMOD * fCKMPU/ (384 * (256-TH1)) 2 SMOD * fCKMPU/(64 * (210-S0REL))

UART1 N/A fCKMPU/(32 * (210-S1REL))

Note: S0REL and S1REL are 10-bit values derived by combining bits from the respective timer reload registers. SMOD is the SMOD bit in the

SFR PCON. TH1 is the high byte of timer 1.

Table 12: Baud Rate Generation

UART 0 UART 1

Mode 0 N/A Start bit, 8 data bits, parity, stop bit, variable baud

rate (internal baud rate generator)

Mode 1 Start bit, 8 data bits, stop bit, variable baud

rate (internal baud rate generator or timer 1)

Start bit, 8 data bits, stop bit, variable baud rate

(internal baud rate generator)

Mode 2 Start bit, 8 data bits, parity, stop bit, fixed

baud rate 1/32 or 1/64 of fCKMPU N/A

Mode 3 Start bit, 8 data bits, parity, stop bit, variable

baud rate (internal baud rate generator or

timer 1)

N/A

Table 13: UART Modes

Parity of serial data is available through the P flag of the accumulator. Seven-bit serial modes with parity, such as

those used by the FLAG protocol, can be simulated by setting and reading bit 7 of 8-bit output data. Seven-bit serial

modes without parity can be simulated by setting bit 7 to a constant 1. 8-bit serial modes with parity can be simulated

by setting and reading the 9th bit, using the control bits TB80 (S0CON.3) and TB81 (S1CON.3) in the S0CON and S1CON

SFRs for transmit and RB81 (S1CON.2) for receive operations. SM20 (S0CON.5) and SM21 (S1CON.5) can be used as

handshake signals for inter-processor communication in multi-processor systems.

Serial Interface 0 Control Register (S0CON).

The function of the UART0 depends on the setting of the Serial Port Control Register S0CON.

MSB LSB

SM0 SM1 SM20 REN0 TB80 RB80 TI0 RI0

Table 14: The S0CON Register

Serial Interface 1 Control Register (S1CON).

The function of the serial port depends on the setting of the Serial Port Control Register S1CON.

MSB LSB

SM - SM21 REN1 TB81 RB81 TI1 RI1

Table 15: The S1CON register

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Bit Symbol Function

S0CON.7 SM0

S0CON.6 SM1

These two bits set the UART0 mode:

Mode Description SM0 SM1

0 N/A 0 0

1 8-bit UART 0 1

2 9-bit UART 1 0

3 9-bit UART 1 1

S0CON.5 SM20 Enables the inter-processor communication feature.

S0CON.4 REN0 If set, enables serial reception. Cleared by software to disable reception.

S0CON.3 TB80 The 9th transmitted data bit in Modes 2 and 3. Set or cleared by the

MPU, depending on the function it performs (parity check, multiprocessor

communication etc.)

S0CON.2 RB80 In Modes 2 and 3 it is the 9th data bit received. In Mode 1, if SM20 is 0,

RB80 is the stop bit. In Mode 0 this bit is not used. Must be cleared by

software

S0CON.1 TI0 Transmit interrupt flag, set by hardware after completion of a serial

transfer. Must be cleared by software.

S0CON.0 RI0 Receive interrupt flag, set by hardware after completion of a serial

reception. Must be cleared by software

Table 16: The S0CON Bit Functions

Bit Symbol Function

S1CON.7 SM Sets the baud rate for UART1

SM Mode Description Baud Rate

0 A 9-bit UART variable

1 B 8-bit UART variable

S1CON.5 SM21 Enables the inter-processor communication feature.

S1CON.4 REN1 If set, enables serial reception. Cleared by software to disable reception.

S1CON.3 TB81 The 9th transmitted data bit in Mode A. Set or cleared by the MPU,

depending on the function it performs (parity check, multiprocessor

communication etc.)

S1CON.2 RB81 In Modes A and B, it is the 9th data bit received. In Mode B, if SM21 is 0,

RB81 is the stop bit. Must be cleared by software

S1CON.1 TI1 Transmit interrupt flag, set by hardware after completion of a serial

transfer. Must be cleared by software.

S1CON.0 RI1 Receive interrupt flag, set by hardware after completion of a serial

reception. Must be cleared by software

Table 17: The S1CON Bit Functions

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Timers and Counters

The 80515 has two 16-bit timer/counter registers: Timer 0 and Timer 1. These registers can be configured for counter or timer

operations.

In timer mode, the register is incremented every machine cycle meaning that it counts up after every 12 periods of the MPU

clock signal.

In counter mode, the register is incremented when the falling edge is observed at the corresponding input signal T0 or T1 (T0

and T1 are the timer gating inputs derived from certain DIO pins, see the DIO Ports chapter). Since it takes two machine

cycles to recognize a 1-to-0 event, the maximum input count rate is 1/2 of the oscillator frequency. There are no restrictions on

the duty cycle, however to ensure proper recognition of 0 or 1 state, an input should be stable for at least 1 machine cycle.

The timers/counters are controlled by the TCON Register

Timer/Counter Control Register (TCON)

MSB LSB

TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0

Table 18: The TCON Register

Bit Symbol Function

TCON.7 TF1

The Timer 1 overflow flag is set by hardware when Timer 1 overflows. This flag

can be cleared by software and is automatically cleared when an interrupt is

processed.

TCON.6 TR1

Timer 1 Run control bit. If cleared, Timer 1 stops.

TCON.5 TF0

Timer 0 overflow flag set by hardware when Timer 0 overflows. This flag can be

cleared by software and is automatically cleared when an interrupt is processed.

TCON.4 TR0

Timer 0 Run control bit. If cleared, Timer 0 stops.

TCON.3 IE1

Interrupt 1 edge flag is set by hardware when the falling edge on external pin

int1 is observed. Cleared when an interrupt is processed.

TCON.2 IT1

Interrupt 1 type control bit. Selects either the falling edge or low level on input

pin to cause an interrupt.

TCON.1 IE0

Interrupt 0 edge flag is set by hardware when the falling edge on external pin

int0 is observed. Cleared when an interrupt is processed.

TCON.0 IT0

Interrupt 0 type control bit. Selects either the falling edge or low level on input

pin to cause interrupt.

Table 19: The TCON Register Bit Functions

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Four operating modes can be selected for Timer 0 and Timer 1. Two Special Function Registers (TMOD and TCON) are used

to select the appropriate mode.

Timer/Counter Mode Control register (TMOD):

MSB LSB

GATE C/T M1 M0 GATE C/T M1 M0

Timer 1 Timer 0

Table 20: The TMOD Register

Bits TR1 (TCON.6) and TR0 (TCON.4) in the TCON register (see Table 18 and Table 19) start their associated timers when set.

Bit Symbol Function

TMOD.7

TMOD.3 Gate If set, enables external gate control (pin int0 or int1 for Counter 0 or 1,

respectively). When int0 or int1 is high, and TRX bit is set (see TCON register), a

counter is incremented every falling edge on T0 or T1 input pin

TMOD.6

TMOD.2 C/T Selects Timer or Counter operation. When set to 1, a Counter operation is

performed. When cleared to 0, the corresponding register will function as a Timer.

TMOD.5

TMOD.1 M1 Selects the mode for Timer/Counter 0 or Timer/Counter 1, as shown in TMOD

description.

TMOD.4

TMOD.0 M0 Selects the mode for Timer/Counter 0 or Timer/Counter 1, as shown in TMOD

description.

Table 21: TMOD Register Bit Description

M1 M0 Mode Function

0 0 Mode 0 13-bit Counter/Timer with 5 lower bits in the TL0 or TL1 register and the

remaining 8 bits in the TH0 or TH1 register (for Timer 0 and Timer 1,

respectively). The 3 high order bits of TL0 and TL1 are held at zero.

0 1 Mode 1 16-bit Counter/Timer.

1 0 Mode 2 8-bit auto-reload Counter/Timer. The reload value is kept in TH0 or TH1,

while TL0 or TL1 is incremented every machine cycle. When TL(x) overflows,

a value from TH(x) is copied to TL(x).

1 1 Mode 3 If Timer 1 M1 and M0 bits are set to '1', Timer 1 stops. If Timer 0 M1 and M0

bits are set to '1', Timer 0 acts as two independent 8-bit Timer/Counters.

Table 22: Timers/Counters Mode Description

Note: In Mode 3, TL0 is affected by TR0 and gate control bits, and sets the TF0 flag on overflow, while

TH0 is affected by the TR1 bit, and the TF1 flag is set on overflow.

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Table 23 specifies the combinations of operation modes allowed for timer 0 and timer 1:

Timer 1

Mode 0 Mode 1 Mode 2

Timer 0 - mode 0 YES YES YES

Timer 0 - mode 1 YES YES YES

Timer 0 - mode 2 Not allowed Not allowed YES

Table 23: Timer Modes

Timer/Counter Mode Control register (PCON):

MSB LSB

SMOD -- -- -- -- -- -- --

Table 24: The PCON Register

The SMOD bit in the PCON register doubles the baud rate when set.

Bit Symbol Function

PCON.7 SMOD

Table 25: PCON Register Bit Description

WD Timer (Software Watchdog Timer)

The software watchdog timer is a 16-bit counter that is incremented once every 24 or 384 clock cycles. After a reset, the

watchdog timer is disabled and all registers are set to zero. The watchdog consists of a 16-bit counter (WDT), a reload register

(WDTREL), prescalers (by 2 and by 16), and control logic. Once the watchdog is started, it cannot be stopped unless the

internal reset signal becomes active.

Note: It is recommended to use the hardware watchdog timer instead of the software watchdog timer.

WD Timer Start Procedure: The WDT is started by setting the SWDT flag. When the WDT register enters the state 0x7CFF,

an asynchronous WDTS signal will become active. The signal WDTS sets bit 6 in the IP0 register and requests a reset state.

WDTS is cleared either by the reset signal or by changing the state of the WDT timer.

Refreshing the WD Timer: The watchdog timer must be refreshed regularly to prevent the reset request signal from becoming

active. This requirement imposes an obligation on the programmer to issue two instructions. The first instruction sets WDT and

the second instruction sets SWDT. The maximum delay allowed between setting WDT and SWDT is 12 clock cycles. If this

period has expired and SWDT has not been set, the WDT is automatically reset, otherwise the watchdog timer is reloaded with

the content of the WDTREL register and the WDT is automatically reset. Since the WDT requires exact timing, firmware needs

to be designed with special care in order to avoid unwanted WDT resets.

TERIDIAN strongly discourages the use of the software WDT.

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Special Function Registers for the WD Timer

Interrupt Enable 0 Register (IEN0):

MSB LSB

EAL WDT ET2 ES0 ET1 EX1 ET0 EX0

Table 26: The IEN0 Register (see also Table 32)

Bit Symbol Function

IEN0.6 WDT Watchdog timer refresh flag.

Set to initiate a refresh of the watchdog timer. Must be set directly before SWDT is

set to prevent an unintentional refresh of the watchdog timer. WDT is reset by

hardware 12 clock cycles after it has been set.

Table 27: The IEN0 Bit Functions (see also Table 32)

Note: The remaining bits in the IEN0 register are not used for watchdog control

Interrupt Enable 1 Register (IEN1):

MSB LSB

EXEN2 SWDT EX6 EX5 EX4 EX3 EX2

Table 28: The IEN1 Register (see also Tables 30/31)

Bit Symbol Function

IEN1.6 SWDT Watchdog timer start/refresh flag.

Set to activate/refresh the watchdog timer. When directly set after setting WDT, a

watchdog timer refresh is performed. Bit SWDT is reset by the hardware 12 clock

cycles after it has been set.

Table 29: The IEN1 Bit Functions (see also Tables 31/32)

Note: The remaining bits in the IEN1 register are not used for watchdog control

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Interrupt Priority 0 Register (IP0):

MSB LSB

-- WDTS IP0.5 IP0.4 IP0.3 IP0.2 IP0.1 IP0.0

Table 30: The IP0 Register (see also Table 45)

Bit Symbol Function

IP0.6 WDTS Watchdog timer status flag. Set when the watchdog timer was started. Can be

read by software.

Table 31: The IP0 bit Functions (see also Table 45)

Note: The remaining bits in the IP0 register are not used for watchdog control

Watchdog Timer Reload Register (WDTREL):

MSB LSB

7 6 5 4 3 2 1 0

Table 32: The WDTREL Register

Bit Symbol Function

WDTREL.7 7 Prescaler select bit. When set, the watchdog is clocked through an additional

divide-by-16 prescaler

WDTREL.6

WDTREL.0

6-0

Seven bit reload value for the high-byte of the watchdog timer. This value is

loaded to the WDT when a refresh is triggered by a consecutive setting of bits

WDT and SWDT.

Table 33: The WDTREL Bit Functions

The WDTREL register can be loaded and read at any time.

Interrupts

The 80515 provides 11 interrupt sources with four priority levels. Each source has its own request flag(s) located in a special

function register (TCON, IRCON, and SCON). Each interrupt requested by the corresponding flag can be individually enabled or

disabled by the enable bits in SFRs IEN0, IEN1, and IEN2.

External interrupts are the interrupts external to the 80515 core, i.e. signals that originate in other parts of the

71M6521BE, for example the CE, DIO, EEPROM interface.

Interrupt Overview

When an interrupt occurs, the MPU will vector to the predetermined address as shown in Table 52. Once interrupt service has

begun, it can be interrupted only by a higher priority interrupt. The interrupt service is terminated by a return from instruction,

"RETI". When an RETI is performed, the processor will return to the instruction that would have been next when the interrupt

occurred.

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When an interrupt occurs, the MPU will vector to the predetermined address as shown in Table 52. Once interrupt service has

begun, it can be interrupted only by a higher priority interrupt. The interrupt service is terminated by a return from instruction,

"RETI". When a RETI instruction is performed, the processor will return to the instruction that would have been next when the

interrupt occurred.

When the interrupt condition occurs, the processor will also indicate this by setting a flag bit. This bit is set regardless of

whether the interrupt is enabled or disabled. Each interrupt flag is sampled once per machine cycle, then samples are polled

by the hardware. If the sample indicates a pending interrupt when the interrupt is enabled, then the interrupt request flag is set.

On the next instruction cycle, the interrupt will be acknowledged by hardware forcing an LCALL to the appropriate vector

address, if the following conditions are met:

• No interrupt of equal or higher priority is already in progress.

• An instruction is currently being executed and is not completed.

• The instruction in progress is not RETI or any write access to the registers IEN0, IEN1, IEN2, IP0 or IP1.

Special Function Registers for Interrupts:

Interrupt Enable 0 register (IE0)

MSB LSB

EAL WDT ES0 ET1 EX1 ET0 EX0

Table 34: The IEN0 Register

Bit Symbol Function

IEN0.7 EAL EAL=0 – disable all interrupts

IEN0.6 WDT Not used for interrupt control

IEN0.5 -

IEN0.4 ES0 ES0=0 – disable serial channel 0 interrupt

IEN0.3 ET1 ET1=0 – disable timer 1 overflow interrupt

IEN0.2 EX1 EX1=0 – disable external interrupt 1

IEN0.1 ET0 ET0=0 – disable timer 0 overflow interrupt

IEN0.0 EX0 EX0=0 – disable external interrupt 0

Table 35: The IEN0 Bit Functions

Interrupt Enable 1 Register (IEN1)

MSB LSB

SWDT EX6 EX5 EX4 EX3 EX2

Table 36: The IEN1 Register

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Bit Symbol Function

IEN1.7 -

IEN1.6 SWDT Not used for interrupt control

IEN1.5 EX6 EX6=0 – disable external interrupt 6

IEN1.4 EX5 EX5=0 – disable external interrupt 5

IEN1.3 EX4 EX4=0 – disable external interrupt 4

IEN1.2 EX3 EX3=0 – disable external interrupt 3

IEN1.1 EX2 EX2=0 – disable external interrupt 2

IEN1.0 -

Table 37: The IEN1 Bit Functions

Interrupt Enable 2 register (IE2)

MSB LSB

- - - - - - - ES1

Table 38: The IEN2 Register

Bit Symbol Function

IEN2.0 ES1 ES1=0 – disable serial channel 1 interrupt

Table 39: The IEN2 Bit Functions

Timer/Counter Control register (TCON)

MSB LSB

TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0

Table 40: The TCON Register

Bit Symbol Function

TCON.7 TF1 Timer 1 overflow flag

TCON.6 TR1 Not used for interrupt control

TCON.5 TF0 Timer 0 overflow flag

TCON.4 TR0 Not used for interrupt control

TCON.3 IE1 External interrupt 1 flag

TCON.2 IT1 External interrupt 1 type control bit

TCON.1 IE0 External interrupt 0 flag

TCON.0 IT0 External interrupt 0 type control bit

Table 41: The TCON Bit Functions

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Timer2/Counter2 Control register (T2CON):

Bit Symbol Function

T2CON.7 -- Not used

T2CON.6 I3FR Polarity control for INT3: 0 - falling edge, 1 – rising edge

T2CON.5 I2FR Polarity control for INT3: 0 - falling edge, 1 – rising edge

TCON.4 …

T2CON0 -- Not used

Table 42: The T2CON Bit Functions

Interrupt Request register (IRCON)

MSB LSB

EX6 IEX5 IEX4 IEX3 IEX2

Table 43: The IRCON Register

Bit Symbol Function

IRCON.7 -

IRCON.6 -

IRCON.5 IEX6 External interrupt 6 edge flag

IRCON.4 IEX5 External interrupt 5 edge flag

IRCON.3 IEX4 External interrupt 4 edge flag

IRCON.2 IEX3 External interrupt 3 edge flag

IRCON.1 IEX2 External interrupt 2 edge flag

IRCON.0 -

Table 44: The IRCON Bit Functions

Note: Only TF0 and TF1 (timer 0 and timer 1 overflow flag) will be automatically cleared by hardware when the

service routine is called (Signals T0ACK and T1ACK – port ISR – active high when the service routine is called).

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External Interrupts

The 71M6521BE MPU allows seven external interrupts. These are connected as shown in Table 45. The direction of interrupts

2 and 3 is programmable in the MPU. Interrupts 2 and 3 should be programmed for falling sensitivity. The generic 8051 MPU

literature states that interrupt 4 through 6 are defined as rising edge sensitive. Thus, the hardware signals attached to

interrupts 5 and 6 are inverted to achieve the edge polarity shown in Table 45.

External

Interrupt Connection Polarity Flag Reset

0 Digital I/O High Priority see DIO_Rx automatic

1 Digital I/O Low Priority see DIO_Rx automatic

2 FWCOL0, FWCOL1 falling automatic

3 CE_BUSY falling automatic

4 PLL_OK (rising), PLL_OK (falling) rising automatic

5 EEPROM busy falling automatic

6 XFER_BUSY falling manual

Table 45: External MPU Interrupts

FWCOLx interrupts occur when the CE collides with a flash write attempt. See the flash write description for more detail.

SFR (special function register) enable bits must be set to permit any of these interrupts to occur. Likewise, each interrupt has

its own flag bit, which is set by the interrupt hardware, and reset by the MPU interrupt handler. Note that XFER_BUSY,

FWCOL0, FWCOL1, PLLRISE, PLLFALL, have their own enable and flag bits in addition to the interrupt 6, 4, and 2 enable and

flag bits.

IE0 through IEX6 are cleared automatically when the hardware vectors to the interrupt handler. The other flags, IE_XFER

through IE_PB, are cleared by writing a zero to them. Since these bits are in a bit-addressable SFR byte, common practice

would be to clear them with a bit operation. This is to be avoided. The hardware implements bit operations as a byte wide read-

modify-write hardware macro. If an interrupt occurs after the read, but before the write, its flag will be cleared unintentionally.

The proper way to clear the flag bits is to write a byte mask consisting of all ones except for a zero in the location of the bit to

be cleared. The flag bits are configured in hardware to ignore ones written to them.

Interrupt Enable Interrupt Flag

Name Location Name Location

Interrupt Description

EX0 SFR A8[[0] IE0 SFR 88[1] External interrupt 0

EX1 SFR A8[2] IE1 SFR 88[3] External interrupt 1

EX2 SFR B8[1] IEX2 SFR C0[1] External interrupt 2

EX3 SFR B8[2] IEX3 SFR C0[2] External interrupt 3

EX4 SFR B8[3] IEX4 SFR C0[3] External interrupt 4

EX5 SFR B8[4] IEX5 SFR C0[4] External interrupt 5

EX6 SFR B8[5] IEX6 SFR C0[5] External interrupt 6

EX_XFER 2002[0] IE_XFER SFR E8[0] XFER_BUSY interrupt (int 6)

IE_FWCOL0 SFR E8[3] FWCOL0 interrupt (int 2)

EX_FWCOL 2007[4] IE_FWCOL1 SFR E8[2] FWCOL1 interrupt (int 2)

IE_PLLRISE SFRE8[6] PLL_OK rise interrupt (int 4)

EX_PLL 2007[5] IE_PLLFALL SFRE8[7] PLL_OK fall interrupt (int 4)

IE_WAKE SFRE8[5] AUTOWAKE flag

IE_PB SFRE8[4] PB flag

Table 46: Interrupt Enable and Flag Bits

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The AUTOWAKE and PB flag bits are shown in Table 46 because they behave similarly to interrupt flags, even though they are

not actually related to an interrupt. These bits are set by hardware when the MPU wakes from a push button or wake timeout.

The bits are reset by writing a zero. Note that the PB flag is set whenever the PB is pushed, even if the part is already awake.

Each interrupt has its own flag bit, which is set by the interrupt hardware and is reset automatically by the MPU interrupt

handler (0 through 5). XFER_BUSY has its own enable and flag bit in addition to the interrupt 6 enable and flag bit (see Table

46), and these interrupts must be cleared by the MPU software.

The external interrupts are connected as shown in Table 46. The polarity of interrupts 2 and 3 is programmable in the MPU via

the I3FR and I2FR bits in T2CON. Interrupts 2 and 3 should be programmed for falling sensitivity. The generic 8051 MPU

literature states that interrupts 4 through 6 are defined as rising edge sensitive. Thus, the hardware signals attached to

interrupts 5 and 6 are inverted to achieve the edge polarity shown in Table 46.

SFR (special function register) enable bits must be set to permit any of these interrupts to occur. Likewise, each interrupt has

its own flag bit that is set by the interrupt hardware and is reset automatically by the MPU interrupt handler (0 through 5).

Interrupt Priority Level Structure

All interrupt sources are combined in groups, as shown in Table 47.

Each group of interrupt sources can be programmed individually to one of four priority levels by setting or clearing one bit in the

special function register IP0 and one in IP1. If requests of the same priority level are received simultaneously, an internal

polling sequence as per Table 51 determines which request is serviced first.

An overview of the interrupt structure is given in Figure 6.

Group

0 External interrupt 0 Serial channel 1 interrupt

1 Timer 0 interrupt - External interrupt 2

2 External interrupt 1 - External interrupt 3

3 Timer 1 interrupt - External interrupt 4

4 Serial channel 0 interrupt - External interrupt 5

5 - - External interrupt 6

Table 47: Priority Level Groups

IEN enable bits must be set to permit any of these interrupts to occur. Likewise, each interrupt has its own flag bit that is set by

the interrupt hardware and is reset automatically by the MPU interrupt handler (0 through 5). XFER_BUSY has its own enable

and flag bit in addition to the interrupt 6 enable and flag bit (see Table 46) and this interrupt must be cleared by the MPU

software.

Interrupt Priority 0 Register (IP0)

MSB LSB

-- WDTS IP0.5 IP0.4 IP0.3 IP0.2 IP0.1 IP0.0

Table 48: The IP0 Register

Note: WDTS is not used for interrupt controls

Interrupt Priority 1 Register (IP1)

MSB LSB

- - IP1.5 IP1.4 IP1.3 IP1.2 IP1.1 IP1.0

Table 49: The IP1 Register:

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IP1.x IP0.x Priority Level

0 0 Level0 (lowest)

0 1 Level1

1 0 Level2

1 1 Level3 (highest)

Table 50: Priority Levels

External interrupt 0

Serial channel 1 interrupt

Timer 0 interrupt

External interrupt 2

External interrupt 1

External interrupt 3

Timer 1 interrupt

External interrupt 4

Serial channel 0 interrupt

External interrupt 5

External interrupt 6

Polling sequence

Table 51: Interrupt Polling Sequence

Interrupt Sources and Vectors

Table 52 shows the interrupts with their associated flags and vector addresses.

Interrupt Request Flag Description Interrupt Vector Address

IE0 External interrupt 0 0x0003

TF0 Timer 0 interrupt 0x000B

IE1 External interrupt 1 0x0013

TF1 Timer 1 interrupt 0x001B

RI0/TI0 Serial channel 0 interrupt 0x0023

RI1/TI1 Serial channel 1 interrupt 0x0083

IEX2 External interrupt 2 0x004B

IEX3 External interrupt 3 0x0053

IEX4 External interrupt 4 0x005B

IEX5 External interrupt 5 0x0063

IEX6 External interrupt 6 0x006B

Table 52: Interrupt Vectors

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IE0

Individual

Interrupt

Flags

RI1

TI1

General

Interrupt

Flags

Internal/

External

Source

>=1

TF0

INT2

IE1

INT3

TF1

INT4

RI0

TI0

>=1

INT5

INT6

IRCON.1

I2FR

IRCON.2

I3FR

IRCON.3

IRCON.4

IRCON.5

IEN0.7

IP1.0/

IP0.0

IP1.1/

IP0.1

IP1.2/

IP0.2

IP1.3/

IP0.3

IP1.4/

IP0.4

IP1.5/

IP0.5

Interrupt

Control

Priority

Assignment

Interrupt

Vector

Polling Sequence

Interrupt

Enable

Logic and

Polarity

Selection

DIO

UART1

(optical)

Timer 0

DIO

Timer 1

CE_BUSY

UART0

EEPROM/

I2C

XFER_BUSY

RTC_1S

IEN0.0

IEN2.0

IEN0.1

IEN1.1

IEN0.2

IEN1.2

IEN0.3

IEN1.3

IEN0.4

IEN1.4

IEN1.5

IE_XFER

IE_RTC

Flash Write

Collision

IE_FWCOL0

IE_FWCOL1

PLL OK

IE_PLLRISE

IE_PLLFALL

Figure 6: Interrupt Structure

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On-Chip Resources

Oscillator

The 71M6521BE oscillator drives a standard 32.768kHz watch crystal. These crystals are accurate and do not require a high-

current oscillator circuit. The 71M6521BE oscillator has been designed specifically to handle these crystals and is compatible

with their high impedance and limited power handling capability.

PLL and Internal Clocks

Timing for the device is derived from the 32.768kHz oscillator output. On-chip timing functions include the MPU master clock

and the delta-sigma sample clock. In addition, the MPU has two general counter/timers (see MPU section).

The ADC master clock, CKADC, is generated by an on-chip PLL. It multiplies the oscillator output frequency (CK32) by 150.

The CE clock frequency is always CK32 * 150, or 4.9152MHz, where CK32 is the 32kHz clock. The MPU clock frequency is

determined by MPU_DIV and can be 4.9152MHz *2-MPU_DIV Hz where MPU_DIV varies from 0 to 7 (MPU_DIV is 0 on power-

up). This makes the MPU clock scalable from 4.9152MHz down to 38.4kHz. The circuit also generates a 2x MPU clock for use

by the emulator. This clock is not generated when ECK_DIS is asserted by the MPU.

The setting of MPU_DIV is maintained when the device transitions to BROWNOUT mode, but the time base in BROWNOUT

mode is 28,672Hz.

Temperature Sensor

The device includes an on-chip temperature sensor for determining the temperature of the bandgap reference. The MPU may

request an alternate multiplexer frame containing the temperature sensor output by asserting MUX_ALT. The primary use of

the temperature data is to determine the magnitude of compensation required to offset the thermal drift in the system (see

section titled “Temperature Compensation”).

Physical Memory

Flash Memory: The 71M6521 includes 8KB of on-chip flash memory. The flash memory primarily contains MPU and CE

program code. It also contains images of the CE DRAM, MPU RAM, and I/O RAM. On power-up, before enabling the CE, the

MPU copies these images to their respective locations.

Allocated flash space for the CE program cannot exceed 1024 words (2KB). The CE program must begin on a 1KB boundary

of the flash address. The CE_LCTN[4:0] word defines which 1KB boundary contains the CE code. Thus, the first CE instruction

is located at 1024*CE_LCTN[4:0]. The CE_LCTN[4:0] register must be set before the CE is enabled.

The flash memory is segmented into 512 byte individually erasable pages.

The CE engine cannot access its program memory when flash write occurs. Thus, the flash write procedure is to begin a

sequence of flash writes when CE_BUSY falls (CE_BUSY interrupt) and to make sure there is sufficient time to complete the

sequence before CE_BUSY rises again. The actual time for the flash write operation will depend on the exact number of cycles

required by the CE program. Typically (CE program is 512 instructions, mux frame is 13 CK32 cycles), there will be 200µs of

flash write time, enough for 4 bytes of flash write. If the CE code is shorter, there will be even more time.

Two interrupts warn of collisions between the 8051 firmware and the CE timing. If a flash write is attempted while the CE is

busy, the flash write will not execute and the FW_COL0 interrupt will be issued. If a flash write is still in progress when the CE

would otherwise begin a code pass, the code pass is skipped, the write is completed, and the FW_COL1 interrupt is issued.

The bit FLASH66Z (see I/O RAM table) defines the speed for accessing flash memory. To minimize supply current draw, this bit

should be set to 1.

Flash erasure is initiated by writing a specific data pattern to specific SFR registers in the proper sequence. These special

pattern/sequence requirements prevent inadvertent erasure of the flash memory.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

The mass erase sequence is:

1. Write 1 to the FLSH_MEEN bit (SFR address 0xB2[1].

2. Write pattern 0xAA to FLSH_ERASE (SFR address 0x94)

The mass erase cycle can only be initiated when the ICE port is enabled.

The page erase sequence is:

1. Write the page address to FLSH_PGADR (SFR address 0xB7[7:1]

2. Write pattern 0x55 to FLSH_ERASE (SFR address 0x94)

The MPU may write to the flash memory. This is one of the non-volatile storage options available to the user in addition to

external EEPROM.

FLSH_PWE (flash program write enable) differentiates 80515 data store instructions (MOVX@DPTR,A) between Flash and

XRAM writes.

Updating individual bytes in flash memory:

The original state of a flash byte is 0xFF (all ones). Once, a value other than 0xFF is written to a flash memory cell, overwriting

with a different value usually requires that the cell is erased first. Since cells cannot be erased individually, the page has to be

copied to RAM, followed by a page erase. After this, the page can be updated in RAM and then written back to the flash

memory.

MPU RAM: The 71M6521BE includes 2K-bytes of static RAM memory on-chip (XRAM) plus 256-bytes of internal RAM in the

MPU core. The 2K-bytes of static RAM are used for data storage during normal MPU operations.

CE DRAM: The CE DRAM is the working data memory of the CE (128 32-bit words). The MPU can read and write the CE

DRAM as the primary means of data communication between the two processors.

Optical Interface

The device includes an interface to implement an IR/optical port. The pin OPT_Tx is designed to directly drive an external LED

for transmitting data on an optical link. The pin OPT_RX is designed to sense the input from an external photo detector used

as the receiver for the optical link. These two pins are connected to a dedicated UART port (UART1).

The OPT_TX and OPT_RX pins can be inverted with configuration bits OPT_TXINV and OPT_RXINV, respectively.

Additionally, the OPT_TX output may be modulated at 38kHz. Modulation is available when system power is present (i.e. not

in BROWNOUT mode). The OPT_TXMOD bit enables modulation. Duty cycle is controlled by OPT_FDC[1:0], which can select

50%, 25%, 12.5%, and 6.25% duty cycle. 6.25% duty cycle means OPT_TX is low for 6.25% of the period. Figure 7 illustrates

the OPT_TX generator.

When not needed for the optical UART, the OPT_TX pin can alternatively be configured as DIO2 or WPULSE. The

configuration bits are OPT_TXE[1:0]. Likewise, OPT_RX can alternately be configured as DIO_1. Its control is OPT_RXDIS.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

OPT_TXINV

from OPT_TX UART MOD

EN DUTY

OPT_TX

OPT_TXMOD

OPT_FDC

OPT_TXE[1:0]

V3P3

Internal

OPT_TXMOD=0

OPT_TXMOD=1,

OPT_FDC=2 (25%)

1/38kHz

DIO2

WPULSE

Figure 7: Optical Interface

Digital I/O

The device includes up to 14 pins of general purpose digital I/O. These pins are compatible with 5V inputs (no current-limiting

resistors are needed). Some are dual function that can alternatively be used as LCD drivers (DIO4-11, 14-17) and some share

functions with the optical port (DIO1, DIO2). On reset or power-up, all DIO pins are inputs until they are configured for the

desired direction under MPU control. The pins are configured by the DIO registers and by the five bits of the LCD_NUM

register (located in I/O RAM). Once declared as DIO, each pin can be configured independently as an input or output with the

DIO_DIRn bits. A 3-bit configuration word, DIO_Rx, can be used for certain pins, when configured as DIO, to individually assign

an internal resource such as an interrupt or a timer control. Table 53 lists the direction registers and configurability associated

with each group of DIO pins. Table 54 shows the configuration for a DIO pin through its associated bit in its DIO_DIR register.

Tables showing the relationship between LCD_NUM and the available segment/DIO pins can be found in the Applications

section and in the I/O RAM Description under LCD_NUM[4:0].

DIO PB 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Pin number 62 57 3 -- 37 38 39 40 41 42 43 44 -- -- 20 21

0 1 2 -- 4 5 6 7 0 1 2 3 -- -- 6 7

Data Register DIO0=P0 (SFR 0x80) DIO1=P1 (SFR 0x90)

0 1 2 -- 4 5 6 7 0 1 2 3 -- -- 6 7

Direction Register DIO_DIR0 (SFR 0xA2) DIO_DIR1 (SFR 0x91)

Internal Resources

Configurable Y Y Y -- Y Y Y Y Y Y Y Y -- -- -- --

DIO 16 17 18 19 20 21 22 23

Pin number 22 12 -- -- -- -- -- --

0 1 -- -- -- -- -- --

Data Register DIO2=P2 (SFR 0xA0)

0 1 -- -- -- -- -- --

Direction Register DIO_DIR2 (SFR 0xA1)

Internal Resources

Configurable N N -- -- -- -- -- --

Table 53: Data/Direction Registers and Internal Resources for DIO Pin Groups

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DIO_DIR [n]

0 1

DIO Pin n Function Input Output

Table 54: DIO_DIR Control Bit

Additionally, if DIO6 is declared an output, it can be configured as dedicated pulse output (WPULSE = DIO6) using the

DIO_PW register. In this case, DIO6 is under CE control. DIO4 and DIO5 can be configured to implement the EEPROM

Interface.

The PB pin is a dedicated digital input. If the optical UART is not used, OPT_TX and OPT_RX can be configured as dedicated

DIO pins (DIO1, DIO2, see Optical Interface section).

A 3-bit configuration word, I/O RAM register, DIO_Rx (0x2009[2:0] through 0x200E[6:4]) can be used for certain pins, when

configured as DIO, to individually assign an internal resource such as an interrupt or a timer control (see Table 55 for DIO pins

available for this option). This way, DIO pins can be tracked even if they are configured as outputs.

Tracking DIO pins configured as outputs is useful for pulse counting without external hardware.

When driving LEDs, relay coils etc., the DIO pins should sink the current into GNDD (as shown in Figure 8,

right), not source it from V3P3D (as shown in Figure 8, left). This is due to the resistance of the internal

switch that connects V3P3D to either V3P3SYS or VBAT.

When configured as inputs, the dual-function (DIO/SEG) pins should not be pulled above V3P3SYS in

MISSION and above VBAT in LCD and BROWNOUT modes. Doing so will distort the LCD waveforms of the

other pins. This limitation applies to any pin that can be configured as a LCD driver.

71M6521B

Not recommended

DIO1

V3P3D

LED

V3P3SYS 3.3V

DGND

VBAT

71M6521B

Not recommended

DIO1

V3P3D

LED

V3P3SYS

Recommended

LED

3.3V

DGND

VBAT

Figure 8: Connecting an External Load to DIO Pins

The PB pin is a dedicated digital input. In addition, if the optical UART is not used, OPT_TX and OPT_RX can be configured

as dedicated DIO pins DIO1 and DIO2. Thus, in addition to the 12 general-purpose DIO pins (DIO4…DIO11, DIO14…DIO17),

there are three additional pins that can be used for digital input and output.

DIO1

V3P3D

71M6521B

V3P3SYS

DGND

VBAT

3.3V

Recommended

LED

DIO1

V3P3D

71M6521B

V3P3SYS

DGND

VBAT

3.3V

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Energy Meter IC

DATA SHEET

JANUARY 2008

The control resources selectable for the DIO pins are listed in Table 55. If more than one input is connected to the same

resource, the resources are combined using a logical OR.

DIO_R Value Resource Selected for DIO Pin

0 NONE

1 Reserved

2 T0 (counter0 clock)

3 T1 (counter1 clock)

4 High priority I/O interrupt (INT0 rising)

5 Low priority I/O interrupt (INT1 rising)

6 High priority I/O interrupt (INT0 falling)

7 Low priority I/O interrupt (INT1 falling)

Table 55: Selectable Controls using the DIO_DIR Bits

LCD Drivers

The device contains 20 dedicated LCD segment drivers in addition to the 15 multi-use pins described above. Thus, the device

is capable of driving between 80 to 140 pixels of LCD display with 25% duty cycle (or 60 to 105 pixels with 33% duty cycle). At

eight pixels per digit, this corresponds to 10 to 17 digits.

The LCD drivers are grouped into 4 commons and 35 segment drivers. The LCD interface is flexible and can drive either digit

segments or enunciator symbols.

Segment drivers SEG18 and SEG19 can be configured to blink at either 0.5Hz or 1Hz. The blink rate is controlled by LCD_Y.

There can be up to four pixels/segments connected to each of these drivers. LCD_BLKMAP18[3:0] and LCD_BLKMAP19[3:0]

identify which pixels, if any, are to blink.

LCD interface memory is powered by the non-volatile supply. The bits of the LCD memory are preserved in

LCD and SLEEP modes, even if their pin is not configured as SEG. In this case, they can be useful as general-

purpose non-volatile storage.

Battery Monitor

The battery voltage is measured by the ADC during alternative MUX frames if the BME (Battery Measure Enable) bit is set.

While BME is set, an on-chip 45kΩ load resistor is applied to the battery and a scaled fraction of the battery voltage is applied

to the ADC input. After each alternative MUX frame, the result of the ADC conversion is available at CE DRAM address 0x07.

BME is ignored and assumed zero when system power is not available. See the Battery Monitor section of the Electrical

Specification section for details regarding the ADC LSB size and the conversion accuracy.

EEPROM Interface

The 71M6521BE provides hardware support for either type of EEPROM interface, a two-pin interface and a three-pin interface.

The interfaces use the EECTRL and EEDATA registers for communication.

Two-Pin EEPROM Interface

The dedicated 2-pin serial interface communicates with external EEPROM devices. The interface is multiplexed onto DIO4

(SCK) and DIO5 (SDA) controlled by the DIO_EEX bit (see I/O RAM Table). The MPU communicates with the interface

through two SFR registers: EEDATA and EECTRL. If the MPU wishes to write a byte of data to EEPROM, it places the data in

EEDATA and then writes the ‘Transmit’ command (CMD = 0011) to EECTRL. The write to EECTRL initiates the transmit

operation. The transmit operation is finished when the BUSY bit falls. INT5 is also asserted when BUSY falls. The MPU can

then check the RX_ACK bit to see if the EEPROM acknowledged the transmission.

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A byte is read by writing the ‘Receive’ command (CMD = 0001) to EECTRL and waiting for the BUSY bit to fall. Upon comple-

tion, the received data is in EEDATA. The serial transmit and receive clock is 78kHz during each transmission, and the clock is

held in a high state until the next transmission. The bits in EECTRL are shown in Table 56.

The EEPROM interface can also be operated by controlling the DIO4 and DIO5 pins directly. However, controlling

DIO4 and DIO5 directly is discouraged, because it may tie up the MPU to the point where it may become too

busy to process interrupts.

Status

Bit Name Read/

Write

Reset

State Polarity Description

7 ERROR R 0 Positive 1 when an illegal command is received.

6 BUSY R 0 Positive 1 when serial data bus is busy.

5 RX_ACK R 1 Negative 0 indicates that the EEPROM sent an ACK bit.

4 TX_ACK R 1 Negative 0 indicates when an ACK bit has been sent to the EEPROM

3-0 CMD[3:0] W 0000

Positive,

see CMD

Table

CMD Operation

0000 No-op. Applying the no-op command will stop the I2C clock

(SCK, DIO4). Failure to issue the no-op command will keep

the SCK signal toggling.

0010 Receive a byte from EEPROM and send ACK.

0011 Transmit a byte to EEPROM.

0101 Issue a ‘STOP’ sequence.

0110 Receive the last byte from EEPROM and do not send ACK.

1001 Issue a ‘START’ sequence.

Others No Operation, set the ERROR bit.

Table 56: EECTRL Status Bits

Three-Wire EEPROM Interface

A 500kHz three-wire interface, using SDATA, SCK, and a DIO pin for CS is available. The interface is selected with

DIO_EEX=3. The same 2-wire EECTRL register is used, except the bits are reconfigured, as shown in Table 57. When EECTRL

is written, up to 8 bits from EEDATA are either written to the EEPROM or read from the EEPROM, depending on the values of

the EECTRL bits.The timing diagrams in Figure 9 through Figure 13 describe the 3-wire EEPROM interface behavior. All

commands begin when the EECTRL register is written. Transactions start by first raising the DIO pin that is connected to CS.

Multiple 8-bit or less commands such as those shown in Figure 9 through Figure 13 are then sent via EECTRL and EEDATA.

When the transaction is finished, CS must be lowered. At the end of a Read transaction, the EEPROM will be driving SDATA,

but will transition to HiZ (high impedance) when CS falls. The firmware should then immediately issue a write command with

CNT=0 and HiZ=0 to take control of SDATA and force it to a low-Z state.

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Energy Meter IC

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Control

Bit Name Read/Write Description

7 WFR W

Wait for Ready. If this bit is set, the trailing edge of BUSY will be delayed

until a rising edge is seen on the data line. This bit can be used during the

last byte of a Write command to cause the INT5 interrupt to occur when the

EEPROM has finished its internal write sequence. This bit is ignored if

HiZ=0.

6 BUSY R Asserted while serial data bus is busy. When the BUSY bit falls, an INT5

interrupt occurs.

5 HiZ W Indicates that the SD signal is to be floated to high impedance immediately

after the last SCK rising edge.

4 RD W Indicates that EEDATA is to be filled with data from EEPROM.

3-0 CNT[3:0] W

Specifies the number of clocks to be issued. Allowed values are 0 through

8. If RD=1, CNT bits of data will be read MSB first, and right justified into

the low order bits of EEDATA. If RD=0, CNT bits will be sent MSB first to

EEPROM, shifted out of EEDATA’s MSB. If CNT is zero, SDATA will

simply obey the HiZ bit.

Table 57: EECTRL bits for 3-wire interface

SCLK (output)

BUSY (bit)

CNT Cycles (6 shown)

SDATA (output)

Write -- No HiZ

D2D3D4D5D6D7

EECTRL Byte Written INT5

SDATA output Z (LoZ)

Figure 9: 3-Wire Interface. Write Command, HiZ=0.

CNT Cycles (6 shown)

Write -- With HiZ

INT5

EECTRL Byte Written

SCLK (output)

BUSY (bit)

SDATA (output)

D2D3D4D5D6D7

(HiZ)(LoZ)

SDATA output Z

Figure 10: 3-Wire Interface. Write Command, HiZ=1

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Energy Meter IC

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CNT Cycles (8 shown)

READ

D0D1D2D3D4D5

INT5

D6D7

EECTRL Byte Written

SCLK (output)

BUSY (bit)

SDATA (input)

SDATA output Z

(HiZ)

Figure 11: 3-Wire Interface. Read Command.

CNT Cycles (0 shown)

Write -- No HiZ

INT5 not issued

CNT Cycles (0 shown)

Write -- HiZ

INT5 not issued

EECTRL Byte Written EECTRL Byte Written

SCLK (output)

BUSY (bit)

SDATA (output)

SCLK (output)

BUSY (bit)

SDATA (output)

(HiZ)

SDATA output ZSDATA output Z

(LoZ)

Figure 12: 3-Wire Interface. Write Command when CNT=0

CNT Cycles (6 shown)

Write -- With HiZ and WFR

EECTRL Byte Written

SCLK (output)

BUSY (bit)

SDATA (out/in) D2D3D4D5D6D7 BUSY READY

(From EEPROM)

INT5

(From 6520)

SDATA output Z (HiZ)(LoZ)

Figure 13: 3-Wire Interface. Write Command when HiZ=1 and WFR=1.

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Energy Meter IC

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Hardware Watchdog Timerre Watchdog Timer

In addition to the basic watchdog timer included in the 80515 MPU, an independent,

robust, fixed-duration, watchdog timer (WDT) is included in the device. It uses the crystal

oscillator as its time base and must be refreshed by the MPU firmware at least every 1.5

seconds. When not refreshed on time the WDT overflows, and the part is reset as if the

RESET pin were pulled high, except that the I/O RAM bits will be in the same state as after

a wake-up from SLEEP or LCD modes (see the I/O RAM description for a list of I/O RAM

bit states after RESET and wake-up). 4100 oscillator cycles (or 125ms) after the WDT

overflow, the MPU will be launched from program address 0x0000.

V3P3

V3P3 -

400mV

V3P3 - 10mV

VBIAS

Battery

modes

Normal

operation,

WDT

enabled

WDT dis-

abled

A status bit, WD_OVF, is set when WDT overflow occurs. This bit is powered by the

nonvolatile supply and can be read by the MPU when WAKE rises to determine if the part

is initializing after a WD overflow event or after a power-up. After it is read, MPU firmware

must clear WD_OVF. The WD_OVF bit is cleared by the RESET pin

There is no internal digital state that deactivates the WDT. For debug purposes, however,

the WDT can be disabled by tying the V1 pin to V3P3 (see Figure 35). Of course, this also

deactivates V1 power fault detection. Since there is no firmware way to disable the crystal

oscillator or the WDT, it is guaranteed that whatever state the part might find itself in, upon

watchdog overflow, the part will be reset to a known state.

Asserting ICE_E will also deactivate the WDT. This is the only method that will work in

BROWNOUT mode.

In normal operation, the WDT is reset by periodically writing a one to the WDT_RST bit. The

watchdog timer is also reset when the internal signal WAKE=0 (see section on Wake Up

Behavior).

Figure 14: Functions defined by V1.

Program Security

When enabled, the security feature limits the ICE to global flash erase operations only. All other ICE operations are blocked.

This guarantees the security of the user’s MPU and CE program code. Security is enabled by MPU code that is executed in a

32 cycle preboot interval before the primary boot sequence begins. Once security is enabled, the only way to disable it is to

perform a global erase of the flash, followed by a chip reset.

The first 32 cycles of the MPU boot code are called the preboot phase because during this phase the ICE is inhibited. A read-

only status bit, PREBOOT, identifies these cycles to the MPU. Upon completion of preboot, the ICE can be enabled and is

permitted to take control of the MPU.

SECURE, the security enable bit, is reset whenever the chip is reset. Hardware associated with the bit permits only ones to be

written to it. Thus, preboot code may set SECURE to enable the security feature but may not reset it. Once SECURE is set, the

preboot code is protected and no external read of program code is possible

Specifically, when SECURE is set:

• The ICE is limited to bulk flash erase only.

• Page zero of flash memory, the preferred location for the user’s preboot code, may not be page-erased by either

MPU or ICE. Page zero may only be erased with global flash erase.

• Writes to page zero, whether by MPU or ICE are inhibited.

The SECURE bit is to be used with caution! Inadvertently setting this bit will inhibit access to the part via the ICE

interface, if no mechanism for actively resetting the part between reset and erase operations is provided (see ICE

Interface description).

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Energy Meter IC

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Test Ports

TMUXOUT Pin: One out of 16 digital or 8 analog signals can be selected to be output on the TMUXOUT pin. The function of

the multiplexer is controlled with the I/O RAM register TMUX (0x20AA[4:0]), as shown in Table 58.

TMUX[4:0] Mode Function

0 Analog DGND

1 Analog Reserved

2 Analog DGND

3-5 Analog Reserved

6 Analog VBIAS

7 Analog Not used

8-0x0F -- Reserved

0x10 – 0x13 -- Not used

0x14 Digital RTM (Real time output from CE)

0x15 Digital WDTR_EN (Comparator 1 Output AND V1LT3)

0x16 – 0x17 Not used

0x18 Digital RXD (from Optical interface, w/ optional inversion)

0x19 Digital MUX_SYNC

0x1A Digital CK_10M

0x1B Digital CK_MPU

0x1C -- Reserved

0X1E Digital CE_BUSY

0X1F Digital XFER_BUSY

Table 58: TMUX[4:0] Selections

71M6521BE

Energy Meter IC

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FUNCTIONAL DESCRIPTION

Theory of Operation

The energy delivered by a power source into a load can be expressed as:

∫

tdttItVE

)()(

Assuming phase angles are constant, the following formulae apply:

 P = Real Energy [Wh] = V * A * cos φ* t

 Q = Reactive Energy [VARh] = V * A * sin φ * t

 S = Apparent Energy [VAh] = 22 QP +

For a practical meter, not only voltage and current amplitudes, but also phase angles and harmonic content may change

constantly. Thus, simple RMS measurements are inherently inaccurate. A modern solid-state electricity meter IC such as the

TERIDIAN 71M6521BE functions by emulating the integral operation above, i.e. it processes current and voltage samples

through an ADC at a constant frequency. As long as the ADC resolution is high enough and the sample frequency is beyond

the harmonic range of interest, the current and voltage samples, multiplied with the time period of sampling will yield an

accurate quantity for the momentary energy. Summing up the momentary energy quantities over time will result in accumulated

energy.

-500

-400

-300

-200

-100

100

200

300

400

500

0 5 10 15 20

Current [A]

Voltage [V]

Energy per Interval [Ws]

Accumulated Energy [Ws]

Figure 15: Voltage. Current, Momentary and Accumulated Energy

Figure 15 shows the shapes of V(t), I(t), the momentary power and the accumulated energy, resulting from 50 samples of the

voltage and current signals over a period of 20ms. The application of 240VAC and 100A results in an accumulation of 480Ws

(= 0.133Wh) over the 20ms period, as indicated by the Accumulated Energy curve.

The described sampling method works reliably, even in the presence of dynamic phase shift and harmonic distortion.

71M6521BE

Energy Meter IC

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System Timing Summary

Figure 16 summarizes the timing relationships between the input MUX states, the CE_BUSY signal, and the two serial output

streams. In this example, MUX_DIV=4 and FIR_LEN=1 (384). The duration of each MUX frame is 1 + MUX_DIV * 2 if

FIR_LEN=288, and 1 + MUX_DIV * 3 if FIR_LEN=384. An ADC conversion will always consume an integer number of CK32

clocks. Followed by the conversions is a single CK32 cycle where the bandgap voltage is allowed to recover from the change

in CROSS.

Each CE program pass begins when ADC0 (channel IA) conversion begins. Depending on the length of the CE program, it

may continue running until the end of the ADC3 (VB) conversion. CE opcodes are constructed to ensure that all CE code

passes consume exactly the same number of cycles. The result of each ADC conversion is inserted into the CE DRAM when

the conversion is complete. The CE is written to tolerate sudden changes in ADC data. The exact CK count when each ADC

value is loaded into DRAM is shown in Figure 16.

Figure 16 also shows that the serial RTM data stream begins transmitting at the beginning of state ‘S.’ RTM, consisting of 140

CK cycles, will always finish before the next code pass starts.

CK32

MUX STATE 0

MUX_DIV Conversions, MUX_DIV=1 (4 conversions) is shown Settle

ADC MUX Frame

ADC EXECUTION

MUX_SYNC

CE_EXECUTION

RTM

140

MAX CK COUNT

0 450

150

900 1350 1800

ADC0 ADC1 ADC2 ADC3

CK COUNT = CE_CYCLES + floor((CE_CYCLES + 2) / 5)

NOTES:

1. ALL DIMENSIONS ARE 5MHZ CK COUNTS.

2. THE PRECISE FREQUENCY OF CK IS 150*CRYSTAL FREQUENCY = 4.9152MHz.

3. XFER_BUSY OCCURS ONCE EVERY (PRESAMPS * SUM_CYCLES) CODE PASSES.

CE_BUSY

XFER_BUSY

INITIATED BY A CE OPCODE AT END OF SUM INTERVAL

ADC TIMING

CE TIMING

RTM TIMING

123

Figure 16: Timing Relationship between ADC MUX, Compute Engine, and Serial Transfers.

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CKTEST

TMUXOUT/RTM

FLAG

RTM DATA0 (32 bi ts)

LSB

SIGN

LSB

SIGN

RTM DATA1 (32 bi ts)

LSB

SIGN

RTM DATA2 (32 bi ts)

RTM DATA3 (32 bi ts)

0130 31 0130 31 0130 31 0130 31

FLAG FLAG FLAG

MUX_SYNC

CK32

Figure 17: RTM Output Format

Battery Modes

Shortly after system power (V3P3SYS) is applied, the part will be in MISSION mode. MISSION mode means that the part is

operating with system power and that the internal PLL is stable. This mode is the normal operation mode where the part is

capable of measuring energy.

When system power is not available (i.e. when V1<VBIAS), the 71M6521DE/FE can be in one of three battery modes, i.e.

BROWNOUT, LCD, or SLEEP mode. As soon as V1 falls below VBIAS or when the part wakes up under battery power (with

sufficient voltage margin), the part will automatically enter BROWNOUT mode (see Wake Up Behavior section). From

BROWNOUT mode, the MPU may enter either LCD mode or SLEEP mode by setting either the LCD_ONLY or SLEEP I/O RAM

bits (only one bit can be set at the same time in BROWNOUT mode, since setting one bit will already force the part into SLEEP

or LCD mode, disabling the MPU).

Figure 18 shows a state diagram of the various operation modes, with the possible transitions between modes. For information

on the timing of mode transitions refer to Figure 22 through Figure 24.

When V1 falls below VBIAS or the part wakes up under battery power, the part will automatically enter BROWNOUT mode

(see Wake Up Behavior section). From BROWNOUT mode, the part may choose to enter either LCD mode or SLEEP mode,

as controlled by the MPU via the I/O RAM bits LCD_ONLY and SLEEP.

Meters that do not require functionality in the battery modes still need to contain code that brings the chip from

BROWNOUT mode to SLEEP mode. Otherwise, the chip remains in BROWNOUT mode, once the system power is

missing, and consumes more current than intended.

Similarly, meters equipped with batteries need to contain code that transitions the chip to SLEEP mode as soon as the

battery is attached in production. Otherwise, remaining in BROWNOUT mode would add unnecessary drain to the

battery.

The transition from MISSION mode to BROWNOUT mode is signaled by the IE_PLLFALL interrupt flag (in SFR 0xE8[7]). The

transition in the other direction is signaled by the IE_PLLRISE interrupt flag (SFR 0xE8[6]), when the PLL becomes stable.

Transitions from both LCD and SLEEP mode are initiated by wake-up timer timeout conditions or pushbutton events. When the

PB pin is pulled high (pushbutton is pressed), the IE_PB interrupt flag (SFR 0xE8[4]) is set, and when the wake-up timer times

out, the IE_WAKE interrupt flag (SFR 0xE8[5]) is set.

In the absence of system power, if the voltage margin for the LDO regulator providing 2.5V to the internal circuitry becomes too

low to be safe, the part automatically enters sleep mode (BAT_OK false). The battery voltage must stay above 3V to ensure

that BAT_OK remains true. Under this condition, the 71M6521BE stays in SLEEP mode, even if the voltage margin for the

LDO improves (BAT_OK true).

Table 59 shows the circuit functions available in each operating mode.

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BROWNOUT Mode

In BROWNOUT mode, most non-metering digital functions, as shown in Table 59, are active, including ICE, UART, EEPROM,

and LCD. In BROWNOUT mode, a low bias current regulator will provide 2.5 Volts to V2P5 and the nonvolatile V2P5 net. The

regulator has an output called BAT_OK to indicate that it has sufficient overhead. When BAT_OK = 0, the part will enter

SLEEP mode.

The V3P3D output pin is active in BROWNOUT mode, and low-current external components, such as EEPROMs can be

supplied with the current from this pin while the chip is in BROWNOUT mode.

From BROWNOUT mode, the processor can voluntarily enter LCD or SLEEP modes. When system power is restored, the part

will automatically transition from any of the battery modes to mission mode, once the PLL has settled.

The MPU will run at crystal clock rate in BROWNOUT mode. The value of MPU_DIV will be remembered (not changed) as the

part enters and exits BROWNOUT.

While PLL_OK = 0, the I/O RAM bits ADC_E and CE_E are held in zero state disabling both ADC and CE. When PLL_OK falls,

the CE program counter is cleared immediately and all FIR processing halts. Figure 19 shows the functional blocks active in

BROWNOUT mode.

V3P3SYS

rises

V3P3SYS

falls

MISSION

BROWNOUT

LCD

SLEEP or

V1 > VBIAS

V1 <= VBIAS

LCD_ONLY

RESET &

VBAT_OK

RESET

IE_PLLRISE

-> 1 IE_PLLFALL

-> 1

IE_PB -> 1 IE_WAKE ->

timer

RESET &

V3P3SYS

rises

V3P3SYS

rises

VBAT_OK

SLEEP

Figure 18: Operation Modes State Diagram

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

LCD Mode

In LCD mode, the data contained in the LCD_SEG registers is displayed, i.e. up to four LCD segments connected to each of the

pins SEG18 and SEG19 can be made to blink without the involvement of the MPU, which is disabled in LCD mode. The

V3P3D output pin is inactive in LCD mode.

This mode can be exited only by system power up, a timeout of the wake-up timer, or a push button. Figure 20 shows the

functional blocks active in LCD mode.

SLEEP Mode

In SLEEP mode, the battery current is minimized and only the Oscillator is active. The V3P3D output pin is inactive in LCD

mode. This mode can be exited only by system power-up, a timeout of the wake-up timer, or a push button event. Figure 21

shows the functional blocks active in SLEEP mode.

System Power Battery Power (nonvolatile Supply)

Circuit Function

MISSION BROWNOUT LCD SLEEP

CE Yes -- -- --

CE Data RAM Yes Yes -- --

FIR Yes -- -- --

Analog circuits:

PLL, ADC, VREF, BME, etc. Yes -- -- --

MPU clock rate 4.92MHz

(from PLL)

28.672kHz

(7/8 of 32768Hz) -- --

MPU_DIV Yes Yes -- --

ICE Yes Yes -- --

DIO Pins Yes Yes -- --

Watchdog Timer Yes Yes -- --

LCD Yes Yes Yes --

EEPROM Interface (2-wire) Yes Yes (8kb/s) -- --

EEPROM Interface (3-wire) Yes Yes (16kb/s) -- --

UART Yes Yes -- --

Optical TX modulation Yes -- -- --

Flash Read Yes Yes -- --

Flash Page Erase Yes Yes -- --

Flash Write Yes -- -- --

RAM Read and Write Yes Yes -- --

Wakeup Timer Yes Yes Yes Yes

Crystal oscillator Yes Yes Yes Yes

DRAM data preservation Yes Yes -- --

V3P3D voltage output Yes Yes -- --

Table 59: Available Circuit Functions (“—“ means “not active)

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

MUX

XIN

XOUT

VREF

CKADC

CKTEST/

SEG19

32 bit Compute

Engine

MPU

(80515)

CONTROL

OPT_RX/

DIO1

OPT_TX/

DIO2/

WPULSE/

VARPULSE

RESET

VBIAS

EMULATOR

PORT

CE_BUSY

OPTICAL

UART

XFER BUSY

COM0..3

VLC2

LCD DISPLAY

DRIVER

DATA

00-7F

PROG

000-7FF

DATA

0000-FFFF

PROG

0000-1FFF

0000-

1FFF

MPU XRAM

(2KB)

0000-07FF

DIGITAL I/O

CONFIG

(I/O RAM)

2000-20FF

I/O RAM

CE RAM

(0.5KB)

MEMORY SHARE

1000-11FF

32KHz

MUX_SYNC

CKCE

CKMPU

CK32

CE_E

RTM_E

COMP_STAT

POWER FAULT

LCD_E

LCD_CLK

LCD_MODE

DIO

4.9MHz

<4.9MHz

4.9MH z

GNDD

V3P3A

V3P3D

VBAT

VOLT

REG

2.5V to logic

V2P5

MPU_DIV

SUM_CYCLES

PRE_SAMPS

EQU

CKOUT_E

32KHz

TMUXOUT

MPU_RSTZ

FAULTZ

WAKE

TMUX[4:0]

CONFIGURATION

PARAMETERS

GNDA

VBIAS

February 2, 2007

CROSS

CK_GEN

OSC

(32KHz)

CK32

CKOUT_E

MCK

PLL

VREF

VREF_D IS

DIV

ADC

MUX

CTRL

MUX_DIV

CHOP_E

EQU

STRT

MUX

CKFIR

4.9MH z

RTM

SEG34/DIO14 ..

SEG37/DIO17

WPULSE

VARPULSE

WPULSE

VARPULSE

TEST

MODE

LCD_MODE

VLC1

VLC0

LCD_E

<4.9MHz

LCD_NUM

DIO_R

DIO_DIR

LCD_NUM

DIO_PV/PW

MUX_AL T

SEG24/DIO4 ..

SEG31/DIO11

SDCK

SDOUT

SDIN

E_RXTX/SEG38

E_TCLK/SEG33

E_RST/SEG32

FLASH

(8KB)

FLSH66ZT

V3P3A

FIR_LEN

FIR

SEG0..18

EEPROM

INTERFACE

DIO_EE X

CK_2X

ECK_DIS

OPT_TXE

V3P3D

LCD_GEN

X4MHZ

VBIAS

MEMORY

SEG32,33

SEG19,38

E_RXTX

E_TCLK

E_RST (Open Drain)

ICE_E

DIO1,2

VREF_CAL

ΔΣ ADC

CONVERTER

VREF

ADC_E

RTM_0..3

CE_LCTN

PLS_MAXWIDTH

PLS_INTERVAL

PLS_INV

OPT_TXINV

OPT_RXINV

OPT_RXDIS

LCD_BLKMAP

LCD_SEG

LCD_Y

SLEEP

LCD_ONLY

V3P3SYS

TEST

MUX

V3P3D

TEMP VBAT

VBAT

MOD

OPT_TXMOD

OPT_FDC CE_LCTN

Figure 19: Functional Blocks in BROWNOUT Mode (inactive blocks grayed out)

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

MUX

XIN

XOUT

VREF

CKADC

CKTEST/

SEG19

32 bit Compute

Engine

MPU

(80515)

CONTROL

OPT_RX/

DIO1

OPT_TX/

DIO2/

WPULSE/

VARPULSE

RESET

VBIAS

EMULATOR

PORT

CE_BUSY

OPTICAL

UART

XFER BUSY

COM0..3

VLC2

LCD DISPLAY

DRIVER

DATA

00-7F

PROG

000-1FF

DATA

0000-FFFF

PROG

0000-1FFF

0000-

1FFF

MPU

XRAM

(2KB)

0000-07FF

DIGITAL I/O

CONFIG

(I/O RAM)

2000-20FF

I/O RAM

CE RAM

(0.5KB)

MEMORY SHARE

1000-11FF

32KHz

MUX_SYNC

CKCE

CKMPU

CK32

CE_E

RTM_E

COMP_STAT

POWER FAULT

LCD_E

LCD_CLK

LCD_MODE

DIO

4.9MHz

<4.9MHz

4.9MH z

GNDD

V3P3A

V3P3D

VBAT

VOLT

REG

2.5V to logic

V2P5

MPU_DIV

SUM_CYCLES

PRE_SAMPS

EQU

CKOUT_E

32KHz

TMUXOUT

MPU_RSTZ

FAULTZ

WAKE

TMUX[4:0]

CONFIGURATION

PARAMETERS

GNDA

VBIAS

February 2, 2007

CROSS

CK_GEN

OSC

(32KHz)

CK32

CKOUT_E

MCK

PLL

VREF

VREF_D IS

DIV

ADC

MUX

CTRL

MUX_DIV

CHOP_E

EQU

STRT

MUX

CKFIR

4.9MH z

RTM

SEG34/DIO14 ..

SEG37/DIO17

WPULSE

VARPULSE

WPULSE

VARPULSE

TEST

MODE

LCD_MODE

VLC1

VLC0

LCD_E

<4.9MHz

LCD_NUM

DIO_R

DIO_DIR

LCD_NUM

DIO_PV/PW

MUX_AL T

SEG24/DIO4 ..

SEG31/DIO11

SDCK

SDOUT

SDIN

E_RXTX/SEG38

E_TCLK/SEG33

E_RST/SEG32

FLASH

(8KB)

FLSH66ZT

V3P3A

FIR_LEN

FIR

SEG0..18

EEPROM

INTERFACE

DIO_EE X

CK_2X

ECK_DIS

OPT_TXE

V3P3D

LCD_GEN

X4MHZ

VBIAS

MEMORY

SEG32,33

SEG19,38

E_RXTX

E_TCLK

E_RST (Open Drain)

ICE_E

DIO1,2

VREF_CAL

ΔΣ ADC

CONVERTER

VREF

ADC_E

RTM_0..3

CE_LCTN

PLS_MAXWIDTH

PLS_INTERVAL

PLS_INV

OPT_TXINV

OPT_RXINV

OPT_RXDIS

LCD_BLKMAP

LCD_SEG

LCD_Y

SLEEP

LCD_ONLY

V3P3SYS

TEST

MUX

V3P3D

TEMP VBAT

VBAT

MOD

OPT_TXMOD

OPT_FDC

Figure 20: Functional Blocks in LCD Mode (inactive blocks grayed out)

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

MUX

XIN

XOUT

VREF

CKADC

CKTEST/

SEG19

32 bit Compute

Engine

MPU

(80515)

CONTROL

OPT_RX/

DIO1

OPT_TX/

DIO2/

WPULSE/

VARPULSE

RESET

VBIAS

EMULATOR

PORT

CE_BUSY

OPTICAL

UART

XFER BUSY

COM0..3

VLC2

LCD DISPLAY

DRIVER

DATA

00-7F

PROG

000-1FF

DATA

0000-FFFF

PROG

0000-1FFF

0000-

1FFF

MPU

XRAM

(2KB)

0000-07FF

DIGITAL I/O

CONFIG

(I/O RAM)

2000-20FF

I/O RAM

CE RAM

(0.5KB)

MEMORY SHARE

1000-11FF

32KHz

MUX_SYNC

CKCE

CKMPU

CK32

CE_E

RTM_E

COMP_STAT

POWER FAULT

LCD_E

LCD_CLK

LCD_MODE

DIO

4.9MHz

<4.9MHz

4.9MH z

GNDD

V3P3A

V3P3D

VBAT

VOLT

REG

2.5V to logic

V2P5

MPU_DIV

SUM_CYCLES

PRE_SAMPS

EQU

CKOUT_E

32KHz

TMUXOUT

MPU_RSTZ

FAULTZ

WAKE

TMUX[4:0]

CONFIGURATION

PARAMETERS

GNDA

VBIAS

February 2, 2007

CROSS

CK_GEN

OSC

(32KHz)

CK32

CKOUT_E

MCK

PLL

VREF

VREF_D IS

DIV

ADC

MUX

CTRL

MUX_DIV

CHOP_E

EQU

STRT

MUX

CKFIR

4.9MH z

RTM

SEG34/DIO14 ..

SEG37/DIO17

WPULSE

VARPULSE

WPULSE

VARPULSE

TEST

MODE

LCD_MODE

VLC1

VLC0

LCD_E

<4.9MHz

LCD_NUM

DIO_R

DIO_DIR

LCD_NUM

DIO_PV/PW

MUX_AL T

SEG24/DIO4 ..

SEG31/DIO11

SDCK

SDOUT

SDIN

E_RXTX/SEG38

E_TCLK/SEG33

E_RST/SEG32

FLASH

(8KB)

FLSH66ZT

V3P3A

FIR_LEN

FIR

SEG0..18

EEPROM

INTERFACE

DIO_EE X

CK_2X

ECK_DIS

OPT_TXE

V3P3D

LCD_GEN

X4MHZ

VBIAS

MEMORY

SEG32,33

SEG19,38

E_RXTX

E_TCLK

E_RST (Open Drain)

ICE_E

DIO1,2

VREF_CAL

ΔΣ ADC

CONVERTER

VREF

ADC_E

RTM_0..3

CE_LCTN

PLS_MAXWIDTH

PLS_INTERVAL

PLS_INV

OPT_TXINV

OPT_RXINV

OPT_RXDIS

LCD_BLKMAP

LCD_SEG

LCD_Y

SLEEP

LCD_ONLY

V3P3SYS

TEST

MUX

V3P3D

TEMP VBAT

VBAT

MOD

OPT_TXMOD

OPT_FDC

Figure 21: Functional Blocks in SLEEP Mode (inactive blocks grayed out)

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

time

System

Power

(V3P3SYS)

MPU Mode

Battery

Current

Transition

MPU Clock

Source Xtal PLL

(4.2MHz/MUX_DIV)

PLL_OK

MISSION

2048...4096

CK32 cycles

300nA

13..14 CK

cycles

WAKE

BROWNOUT

V1_OK

Figure 22: Transition from BROWNOUT to MISSION Mode when System Power Returns

time

V3P3SYS

and VBAT

MPU Mode

Battery

Current

MPU Clock

Source

Xtal PLL

(4.2MHz)

PLL_OK

MISSION

300nA

WAKE

Internal

RESETZ

BROWN-

OUT

1024 CK32

cycles

14.5 CK32

cycles

4096 CK32

cycles

V1_OK

Figure 23: Power-Up Timing with V3P3SYS and VBAT tied together

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

time

VBAT

MPU Mode

Battery

Current

MPU Clock

Source

Xtal

PLL_OK

WAKE

Internal

RESETZ

1024 CK32

cycles

BROWNOUT

14.5 CK32

cycles

VBAT_OK

Figure 24: Power-Up Timing with VBAT only

Fault and Reset Behavior

Reset Mode: When the RESET pin is pulled high all digital activity stops. The oscillator module continues to run. Additionally,

all I/O RAM bits are set to their default states. As long as V1, the input voltage at the power fault block, is greater than VBIAS,

the internal 2.5V regulator will continue to provide power to the digital section.

Once initiated, the reset mode will persist until the reset timer times out, signified by WAKE rising. This will occur in 4100

cycles of the real time clock after RESET goes low, at which time the MPU will begin executing its preboot and boot sequences

from address 00. See the security section for more description of preboot and boot.

If system power is not present, the reset timer duration will be 2 cycles of the crystal clock, at which time the MPU will begin

executing in BROWNOUT mode, starting at address 00.

Power Fault Circuit: The 71M6521BE includes a comparator to monitor system power fault conditions. When the output of

the comparator falls (V1<VBIAS), the I/P RAM bits PLL_OK is zeroed and the part switches to BROWNOUT mode if a battery

is present. Once, system power returns, the MPU remains in reset and does not start Mission Mode until 4100 oscillator clocks

later, when PLL_OK rises. If a battery is not present, indicated by BAT_OK=0, WAKE will fall and the part will enter SLEEP

mode.

There are several conditions the part could be in as system power returns. If the part is in BROWNOUT mode, it will auto-

matically switch to mission mode when PLL_OK rises. It will receive an interrupt indicating this. No configuration bits will be

reset or reconfigured during this transition.

If the part is in LCD or SLEEP mode when system power returns, it will also switch to mission mode when PLL_OK rises. In

this case, all configuration bits will be in the reset state due to WAKE having been zero. The MPU RAM must be re-initialized.

The hardware watchdog timer will become active when the part enters MISSION mode.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

If there is no battery when system power returns, the part will switch to mission mode when PLL_OK rises. All configuration

bits will be in reset state, and MPU RAM data will be unknown and must be initialized by the MPU.

Wake Up Behavior

As described above, the part will always wake up in mission mode when system power is restored. Additionally, the part will

wake up in BROWNOUT mode when PB rises (push button pressed) or when a timeout of the wake-up timer occurs.

Wake on PB

If the part is in SLEEP or LCD mode, it can be awakened by a rising edge on the PB pin. This pin is normally pulled to GND

and can be pulled high by a push button depression. Before the PB signal rises, the MPU is in reset due to WAKE being low.

When PB rises, WAKE rises and within three crystal cycles, the MPU begins to execute. The MPU can determine whether the

PB signal woke it up by checking the IE_PB flag.

For debouncing, the PB pin is monitored by a state machine operating from a 32Hz clock. This circuit will reject between 31ms

and 62ms of noise. Detection hardware will ignore all transitions after the initial rising edge. This will continue until the MPU

clears the IE_PB bit.

time

System

Power

(V3P3SYS)

MPU Mode

PLL_OK

15 CK32

cycles

WAKE

LCD

PB or wake-

up timer

BROWNOUT

Figure 25: Wake Up Timing

Wake on Timer

If the part is in SLEEP or LCD mode, it can be awakened by the wake-up timer. Until this timer times out, the MPU is in reset

due to WAKE being low. When the wake-up timer times out, the WAKE signal rises and within three crystal cycles, the MPU

begins to execute. The MPU can determine whether the timer woke it by checking the AUTOWAKE interrupt flag (IE_WAKE).

The wake-up timer begins timing when the part enters LCD or SLEEP mode. Its duration is controlled by WAKE_PRD[2:0] and

WAKE_RES. WAKE_RES selects a timer LSB of either 1 minute (WAKE_RES=1) or 2.5 seconds (WAKE_RES=0).

WAKE_PRD[2:0] selects a duration of from 1 to 7 LSBs.

The timer is armed by WAKE_ARM=1. It must be armed at least three crystal clock cycles before SLEEP or LCD_ONLY is

initiated. Setting WAKE_ARM presets the timer with the values in WAKE_RES and WAKE_PRD and readies the timer to start

when the processor writes to SLEEP or LCD_ONLY. The timer is reset and disarmed whenever the processor is awake. Thus, if

it is desired to wake the MPU periodically (every 5 seconds, for example) the timer must be rearmed every time the MPU is

awakened.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

Data Flow

The data flow between CE and MPU is shown in Figure 26. In a typical application, the 32-bit compute engine (CE) sequen-

tially processes the samples from the voltage inputs on pins IA, VA, IB, and VB, performing calculations to measure active

power (Wh). These measurements are then accessed by the MPU, processed further and output using the peripheral devices

available to the MPU.

CE MPU

Pre-

Processor

Post-

Processor

IRQ

Processed

Metering

Data

Pulse

I/O RAM (Configuration RAM)

Samples Data

Figure 26: MPU/CE Data Flow

CE/MPU Communication

Figure 27 shows the functional relationship between CE and MPU. The CE is controlled by the MPU via shared registers in the

I/O RAM and by registers in the CE DRAM. The CE outputs two interrupt signals to the MPU: CE_BUSY and XFER_BUSY,

which are connected to the MPU interrupt service inputs as external interrupts. CE_BUSY indicates that the CE is actively

processing data. This signal will occur once every multiplexer cycle. XFER_BUSY indicates that the CE is updating data to the

output region of the CE DRAM. This will occur whenever the CE has finished generating a sum by completing an accumulation

interval determined by SUM_CYCLES * PRE_SAMPS samples. Interrupts to the MPU occur on the falling edges of the

XFER_BUSY and CE_BUSY signals.

MPU

WPULSE

INTERRUPTS

DISPLAY (me-

mory-mapped

LCD segments)

DIO

EEPROM

(I2C)

SERIAL

(UART0/1)

SAMPLES

(DIO6)

WSUM

ADC

CE_BUSY

XFER_BUSY

Mux Ctrl.

DATA

SAG CONTROL

I/O RAM (CONFIGURATION RAM)

Figure 27: MPU/CE Communication

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

Temperature Measurement

Measurement of absolute temperature uses the on-chip temperature sensor while applying the following formula:

SNTN

T+

−

=))((

In the above formula T is the temperature in °C, N(T) is the ADC count at temperature T, Nn is the ADC count at 25°C, Sn is

the sensitivity in LSB/°C as stated in the Electrical Specifications, and Tn is +25°C.

Example: At 25°C a temperature sensor value of 518,203,584 (Nn) is read by the ADC. At an unknown temperature T the

value 449.648.000 is read at (N(T)). The absolute temperature is then determined by dividing both Nn and N(T) by 512 to

account for the 9-bit shift of the ADC value and then inserting the results into the above formula, using –2220 for LSB/°C:

CCT °=+

−⋅

=3.8525

)2220( 512 4518,203,58-0449.648.00

It is recommended to base temperature measurements on TEMP_RAW_X which is the sum of two consecutive temperature

readings thus being higher by a factor of two than the raw sensor readings.

Temperature Compensation

Temperature Coefficients: The internal voltage reference is calibrated during device manufacture.

The temperature coefficients TC1 and TC2 are given as constants that represent typical component behavior (in µV/°C and

µV/°C2, respectively).

Since TC1 and TC2 are given in µV/°C and µV/°C2, respectively, the value of the VREF voltage (1.195V) has to be

taken into account when transitioning to PPM/°C and PPM/°C2. This means that PPMC = 26.84*TC1/1.195, and

PPMC2 = 1374*TC2/1.195).

Temperature Compensation: The CE provides the bandgap temperature to the MPU, which then may digitally compensate

the power outputs for the temperature dependence of VREF, using the CE register GAIN_ADJ. Since the band gap amplifier is

chopper-stabilized via the CHOP_EN bits, the most significant long-term drift mechanism in the voltage reference is removed.

The MPU, not the CE, is entirely in charge of providing temperature compensation. The MPU applies the following formula to

determine GAIN_ADJ (address 0x12). In this formula TEMP_X is the deviation from nominal or calibration temperature

expressed in multiples of 0.1°C:

14 22_

16385_ PPMCXTEMPPPMCXTEMP

ADJGAIN ⋅

⋅

In a production electricity meter, the 71M6521BE is not the only component contributing to temperature dependency. A whole

range of components (e.g. current transformers, resistor dividers, power sources, filter capacitors) will contribute temperature

effects.

Since the output of the on-chip temperature sensor is accessible to the MPU, temperature-compensation mechanisms

with great flexibility are possible. MPU access to GAIN_ADJ permits a system-wide temperature correction over the

entire meter rather than local to the chip.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

APPLICATION INFORMATION

Connection of Sensors (CT, Resistive Shunt)

Figure 28 and Figure 29 show how resistive dividers, current transformers, and restive shunts are connected to the voltage and

current inputs of the 71M6521BE.

Vout = R * I

out

= R * I

VA = Vin * Rout/(Rout + Rin)

Vin Rin Rout

Figure 28: Resistive Voltage Divider (Left), Current Transformer (Right)

Vout = R * I

out

V3P3

Figure 29: Resistive Shunt

Connecting 5V Devices

All digital input pins of the 71M6521BE are compatible with external 5V devices. I/O pins configured as inputs do not require

current-limiting resistors when they are connected to external 5V devices.

See the cautionary note on the restrictions for combined SEG/DIO pins configured as digital inputs in the Digital I/O

Section.

out

1/N

out

core

out

V3P3

Filter

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

Connecting LCDs

The 71M6521BE has a LCD controller on-chip capable of controlling static or multiplexed LCDs. Figure 30 shows the basic

connection for a LCD.

segments

6521

LCD

commons

Figure 30: Connecting LCDs

Nineteen pins are dedicated LCD segment pins (SEG0 to SEG18). If more pins are needed to drive segments, the dual-

function pins CKTEST/SEG19, E_RXTX/SEG38, E_TCLK/SEG33, and E_RST/SEG32 can be used.

Even more segment pins are available in the form of combined DIO and segment pins (SEG24/DIO4 to SEG31/DIO11,

SEG34/DIO14 to SEG37/DIO17).

The split between DIO and LCD use of the combined pins is controlled with the DIO register LCD_NUM. LCD_NUM can be

assigned any number between 0 and 18. The first dual-purpose pin to be allocated as LCD is SEG37/DIO17. Thus if

LCD_NUM=5, SEG37 will be configured as LCD. The remaining SEG36 to SEG24 will be configured as DIO16 to DIO4. DIO1

and DIO2 are always available, if not used for the optical port.

Pins CKTEST/SEG19, E_RXTX/SEG38, E_TCLK/SEG33, and E_RST/SEG32 are not affected by LCD_NUM.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

LCD_NUM SEG in Addition

to SEG0-SEG19

Total Number of LCD

Segment Pins In-

cluding SEG0-SEG19

DIO Pins in Addition

to DIO1-DIO2

Total Number of DIO

Pins Including DIO1,

DIO2

0 - 19 4-11, 14-17 14

1 - 19 4-11, 14-17 14

2 - 19 4-11, 14-17 14

3 - 19 4-11, 14-17 14

4 - 19 4-11, 14-17 14

5 37 20 4-11, 14-16 13

6 36-37 21 4-11, 14-15 12

7 35-37 22 4-11, 14 11

8 34-37 23 4-11 10

9 34-37 23 4-11 10

10 34-37 23 4-11 10

11 31, 34-37 24 4-10 9

12 30-31, 34-37 25 4-9 8

13 29-31, 34-37 26 4-8 7

14 28-31, 34-37 27 4-7 6

15 27-31, 34-37 28 4-6 5

16 26-31, 34-37 29 4-5 4

17 25-31, 34-37 30 4 3

18 24-31, 34-37 31 None 2

LCD segment numbers are given without CKTEST/SEG19, E_RXTX/SEG38, E_TCLK/SEG33, and

E_RST/SEG32.

Table 60: LCD and DIO Pin Assignment by LCD_NUM

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Connecting I2C EEPROMs

I2C EEPROMs or other I2C compatible devices should be connected to the DIO pins DIO4 and DIO5, as shown in Figure 31.

Pull-up resistors of roughly 10kΩ to V3P3D (to ensure operation in BROWNOUT mode) should be used for both SCL and SDA

signals. The DIO_EEX register in I/O RAM must be set to 01 in order to convert the DIO pins DIO4 and DIO5 to I2C pins SCL

and SDA.

DIO4

DIO5

6521B

EEPROM

SCL

SDA

V3P3D

10kΩ

DIO4

DIO5

6521B

EEPROM

SCL

SDA

V3P3D

10kΩ

Figure 31: I2C EEPROM Connection

Connecting Three-Wire EEPROMs

µWire EEPROMs and other compatible devices should be connected to the DIO pins DIO4 and DIO5, as shown in Figure 32.

DIO5 connects to both the DI and DO pins of the three-wire device. The CS pin must be connected to a vacant DIO pin of the

71M6521BE. A pull-up resistor of roughly 10kΩ to V3P3D (to ensure operation in BROWNOUT mode) should be used for the

DI/DO signals, and the CS pin should be pulled down with a resistor to prevent that the three-wire device is selected on power-

up, before the 71M6521BE can establish a stable signal for CS. The DIO_EEX register in I/O RAM must be set to 10 in order to

convert the DIO pins DIO4 and DIO5 to uWire pins. The pull-up resistor for DIO5 may not be necessary.

10kΩ

DIO4

DIO5

6521B

EEPROM

SCLK

V3P3D

10kΩ

DIOn

10kΩ

DIO4

DIO5

6521B

EEPROM

SCLK

V3P3D

10kΩ

DIOn

10kΩ

Figure 32: Three-Wire EEPROM Connection

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Energy Meter IC

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UART0 (TX/RX)

The RX pin should be pulled down by a 10kΩ resistor and additionally protected by a 100pF ceramic capacitor, as shown in

Figure 33.

71M6521BE

10kΩ

100pF

71M6521BE

RX 10kΩ

100pF RX

Figure 33: Connections for the RX Pin

Optical Interface

The pins OPT_TX and OPT_RX can be used for a regular serial interface, e.g. by connecting a RS-232 transceiver, or they

can be used to directly operate optical components, e.g. an infrared diode and phototransistor implementing a FLAG interface.

Figure 34 shows the basic connections. The OPT_TX pin becomes active when the I/O RAM register OPT_TXDIS is set to 0.

The polarity of the OPT_TX and OPT_RX pins can be inverted with configuration bits OPT_TXINV and OPT_RXINV, re-

spectively.

The OPT_TX output may be modulated at 38kHz when system power is present. Modulation is not available in BROWNOUT

mode. The OPT_TXMOD bit enables modulation. The duty cycle is controlled by OPT_FDC[1:0], which can select 50%, 25%,

12.5%, and 6.25% duty cycle. A 6.25% duty cycle means OPT_TX is low for 6.25% of the period.

The receive pin (OPT_RX) may need an analog filter when receiving modulated optical signals.

With modulation, an optical emitter can be operated at higher current than nominal, enabling it to increase the distance

along the optical path.

If operation in BROWNOUT mode is desired, the external components should be connected to V3P3D.

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OPT_TX

OPT_RX

V3P3SYS

71M6521BE

V3P3SYS

Phototransistor

LED

10kΩ

100pF

OPT_TX

OPT_RX

V3P3SYS

71M6521BE

10kΩ

100pF

V3P3SYS

Phototransistor

LED

Figure 34: Connection for Optical Components

Connecting V1 and Reset Pins

A voltage divider should be used to establish that V1 is in a safe range when the meter is in mission mode (V1 must be lower

than 2.9V in all cases in order to keep the hardware watchdog timer enabled). For proper debugging or loading code into the

71M6521BE mounted on a PCB, it is necessary to have a provision like the header shown above R1 in Figure 35. A shorting

jumper on this header pulls V1 up to V3P3 disabling the hardware watchdog timer.

The parallel impedance of R1 and R2 should be approximately 20 to 30kΩ in order to provide hysteresis for the power fault

monitor.

V3P3

5kΩ

100pF

GND

V3P3

5kΩ

100pF

GND

Figure 35: Voltage Divider for V1

Even though a functional meter will not necessarily need a reset switch, it is useful to have a reset pushbutton for prototyping,

as shown in Figure 36, left side. The RESET signal may be sourced from V3P3SYS (functional in MISSION mode only),

V3P3D (MISSION and BROWNOUT modes), VBAT (all modes, if battery is present), or from a combination of these sources,

depending on the application. When the 71M6521BE is used in an EMI environment, the RESET pin should be protected by

the external components shown in Figure 36, right side. R1 should be in the range of 100Ω and mounted as closely as possible

to the IC.

Since the 71M6521BE generates its own power-on reset, a reset button or circuitry, as shown in Figure 36, left side, is

only required for test units and prototypes.

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Energy Meter IC

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RESET

71M6521

DGND

100Ω

RESET

71M6521

DGND

100Ω

RESET

71M6521

DGND

V3P3D

VBAT/

V3P3D R

Reset

Switch

1kΩ

1nF

10kΩ

RESET

71M6521

DGND

V3P3D

VBAT/

V3P3D R

Reset

Switch

1kΩ

1nF

10kΩ

Figure 36: External Components for the RESET Pin: Push-Button (Left), EMI Circuit (Right)

Connecting the Emulator Port Pins

Capacitors to ground must be used for protection from EMI. Production boards should have the ICE_E pin connected to

ground.

If the ICE pins are used to drive LCD segments, the pull-up resistors should be omitted, as shown in Figure 37, and 22pF

capacitors to GNDD should be used for protection from EMI.

It is important to bring out the ICE_E pin to the programming interface in order to create a way for reprogramming

parts that have the flash SECURE bit (SFR 0xB2[6]) set. Providing access to ICE_E ensures that the part can be reset

between erase and program cycles, which will enable programming devices to reprogram the part. The reset required is im-

plemented with a watchdog timer reset (i.e. the hardware WDT must be enabled).

LCD Segments

(optional)

E_RST

71M6521B

E_RXTX

E_TCLK

62Ω

22pF22pF

ICE_E

V3P3D

E_RST

LCD Segments

(optional) 71M6521B

E_RXTX

E_TCLK

62Ω

22pF 22pF

ICE_E

V3P3D

Figure 37: External Components for the Emulator Interface

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Crystal Oscillator

The oscillator of the 71M6521BE drives a standard 32.768kHz watch crystal. The oscillator has been designed specifically to

handle these crystals and is compatible with their high impedance and limited power handling capability. The oscillator power

dissipation is very low to maximize the lifetime of any battery backup device attached to VBAT.

Board layouts with minimum capacitance from XIN to XOUT will require less battery current. Good layouts will have XIN and

XOUT shielded from each other.

Since the oscillator is self-biasing, an external resistor must not be connected across the crystal.

With a typical 32kHz crystal, the 71M6521BE needs 600 to 650 milliseconds to stabilize the oscillator clock after power-up.

This time is added to the 125ms (4096 CK32 cycles) for the PLL_OK signal to become true which is required for the part to

enter MISSION mode.

Flash Programming

Operational or test code can be programmed into the flash memory using either an in-circuit emulator or the Flash

Programmer Module (TFP-1) available from TERIDIAN. The flash programming procedure uses the E_RST, E_RXTX, and

E_TCLK pins.

MPU Firmware Library

All application-specific MPU functions mentioned above under “Application Information” are available from TERIDIAN as a

standard ANSI C library and as ANSI “C” source code. The code is available as part of the Demonstration Kit for the

71M6521BE IC. The Demonstration Kits come with the 71M6521BE IC preprogrammed with demo firmware mounted on a

functional sample meter PCB (Demo Board). The Demo Boards allow for quick and efficient evaluation of the IC without having

to write firmware or having to supply an in-circuit emulator (ICE).

Meter Calibration

Once the TERIDIAN 71M6521BE energy meter device has been installed in a meter system, it has to be calibrated for

tolerances of the current sensors, voltage dividers and signal conditioning components. The device can be calibrated using the

gain and phase adjustment factors accessible to the CE. The gain adjustment is used to compensate for tolerances of

components used for signal conditioning, especially the resistive components. Phase adjustment is provided to compensate for

phase shifts introduced by the current sensors.

Due to the flexibility of the MPU firmware, any calibration method, such as calibration based on energy, or current and voltage

can be implemented. It is also possible to implement segment-wise calibration (depending on current range).

The 71M6521BE supports common industry standard calibration techniques, such as single-point (energy-only), multi-point

(energy, Vrms, Irms), and auto-calibration.

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FIRMWARE INTERFACE

I/O RAM MAP – In Numerical Order

‘Not Used’ bits are grayed out, contain no memory and are read by the MPU as zero. RESERVED bits may be in use and

should not be changed. This table lists only the SFR registers that are not generic 8051 SFR registers.

Name Addr Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Configuration:

CE0 2000 EQU[2:0] CE_E Reserved

CE1 2001 PRE_SAMPS[1:0] SUM_CYCLES[5:0]

CE2 2002 MUX_DIV[1:0] CHOP_E[1:0] RTM_E WD_OVF

Reserved* EX_XFR

COMP0 2003 Not Used PLL_OK Not Used Reserved Reserved Reserved

COMP_STAT[0]

CONFIG0 2004 VREF_CAL PLS_INV CKOUT_E[1:0] VREF_DIS MPU_DIV[2:0]

CONFIG1 2005 Reserved Reserved ECK_DIS FIR_LEN ADC_E MUX_ALT FLSH66Z Reserved

VERSION 2006 VERSION[7:0]

CONFIG2 2007 OPT_TXE[1:0] EX_PLL EX_FWCOL Reserved OPT_FDC[1:0]

CE3 20A8 Not Used Not Used Not Used CE_LCTN[4:0]

WAKE 20A9

WAKE_ARM SLEEP LCD_ONLY Not Used WAKE_RES WAKE_PRD[2:0]

TMUX 20AA Not Used Not Used Not Used TMUX[4:0]

Digital I/O:

DIO0 2008 DIO_EEX[1:0] OPT_RXDIS OPT_RXINV DIO_PW DIO_PV

OPT_TXMOD OPT_TXINV

DIO1 2009 Not Used DIO_R1[2:0] Not Used DI_RPB[2:0]

DIO2 200A Not Used Reserved Not Used DIO_R2[2:0]

DIO3 200B Not Used DIO_R5[2:0] Not Used DIO_R4[2:0]

DIO4 200C Not Used DIO_R7[2:0] Not Used DIO_R6[2:0]

DIO5 200D Not Used DIO_R9[2:0] Not Used DIO_R8[2:0]

DIO6 200E Not Used DIO_R11[2:0] Not Used DIO_R10[2:0]

WE 201F Reserved

LCD Display Interface:

LCDX 2020 Not Used BME Reserved LCD_NUM[4:0]

LCDY 2021 Not Used LCD_Y LCD_E LCD_MODE[2:0] LCD_CLK[1:0]

LCDZ 2022 Not Used Not Used Not Used Reserved

LCD0 2030 Not Used LCD_SEG0[3:0]

… … Not Used …

LCD19 2043 Not Used LCD_SEG19[3:0]

LCD24 2048 Not Used LCD_SEG24[3:0]

… … Not Used …

LCD38 2056 Not Used LCD_SEG38[3:0]

LCD_BLNK

205A LCD_BLKMAP19[3:0] LCD_BLKMAP18[3:0]

* Must be set to 0 (CE2 bit 1)

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RTM Probes:

RTM0 2060 RTM0[7:0]

RTM1 2061 RTM1[7:0]

RTM2 2062 RTM2[7:0]

RTM3 2063 RTM3[7:0]

Pulse Generator:

PLS_W 2080 PLS_MAXWIDTH[7:0]

PLS_I 2081 PLS_INTERVAL[7:0]

SFR MAP (SFRs Specific to TERIDIAN 80515) – In Numerical Order

‘Not Used’ bits are blacked out and contain no memory and are read by the MPU as zero. RESERVED bits are in use and

should not be changed. This table lists only the SFR registers that are not generic 8051 SFR registers

Name SFR Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Digital I/O:

DIO7 80 DIO_0[7:4] (Port 0) Reserved DIO_0[2:1] PB

DIO8 A2 DIO_DIR0[7:4] Reserved DIO_DIR0[2:1] Reserved

DIO9 90 DIO_1[7:6] Reserved DIO_1[3:0] (Port 1)

DIO10 91 DIO_DIR1[7:6] Reserved DIO_DIR1[3:0]

DIO11 A0 Not Used Not Used Reserved Reserved DIO_2[1:0] (Port 2)

DIO12 A1 Not Used Not Used Reserved Reserved DIO_DIR2[1:0]

Interrupts and WD Timer:

INTBITS F8 INT6 INT5 INT4 INT3 INT2 INT1 INT0

IFLAGS E8

IE_PLLFALL

WD_RST IE_PLLRISE IE_WAKE IE_PB IE_FWCOL1 IE_FWCOL0 Reserved IE_XFER

Flash:

ERASE 94 FLSH_ERASE[7:0]

FLSHCTL B2 PREBOOT SECURE Not Used Not Used Not Used Not Used FLSH_MEEN FLSH_PWE

PGADR B7 FLSH_PGADR[6:0] Not Used

Serial EEPROM:

EEDATA 9E EEDATA[7:0]

EECTRL 9F EECTRL[7:0]

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I/O RAM DESCRIPTION – Alphabetical Order

Bits with a W (write) direction are written by the MPU into configuration RAM. Typically, they are initially stored in flash memory

and copied to the configuration RAM by the MPU. Some of the more frequently programmed bits are mapped to the MPU SFR

memory space. The remaining bits are mapped to 2xxx. Bits with R (read) direction can be read by the MPU. Columns labeled

Rst and Wk describe the bit values upon reset and wake, respectively. No entry in one of these columns means the bit is

either read-only or is powered by the nonvolatile supply and is not initialized. Write only bits will return zero when they are read.

Name Location Rst Wk Dir Description

ADC_E 2005[3] 0 0 R/W Enables ADC and VREF. When disabled, removes bias current

BME 2020[6] 0 - R/W Battery Measure Enable. When set, a load current is immediately

applied to the battery and it is connected to the ADC to be measured

on Alternative Mux Cycles. See MUX_ALT bit.

CE_E 2000[4] 0 0 R/W CE enable.

CE_LCTN[4:0] 20A8[4:0] 1F 1F

R/W CE program location. The starting address for the CE program is

1024*CE_LCTN. CE_LCTN must be defined before the CE is

started.

CHOP_E[1:0] 2002[5:4] 0 0 R/W

Chop enable for the reference bandgap circuit. The value of CHOP

will change on the rising edge of MUXSYNC according to the value

in CHOP_E:

00-toggle1 01-positive 10-reversed 11-toggle

1except at the mux sync edge at the end of SUMCYCLE.

CKOUT_E[1:0] 2004[5,4] 00 00 R/W

CKTEST Enable. The default is 00

00-SEG19,

01-CK_FIR (5MHz Mission, 32kHz Brownout)

10-Not allowed (reserved for production test)

11-Same as 10.

COMP_STAT[0] 2003[0] -- -- R The status of the power fail comparator for V1.

DI_RPB[2:0]

DIO_R1[2:0]

DIO_R2[2:0]

DIO_R4[2:0]

DIO_R5[2:0]

DIO_R6[2:0]

DIO_R7[2:0]

DIO_R8[2:0]

DIO_R9[2:0]

DIO_R10[2:0]

DIO_R11[2:0]

2009[2:0]

2009[6:4]

200A[2:0]

200B[2:0]

200B[6:4]

200C[2:0]

200C[6:4]

200D[2:0]

200D[6:4]

200E[2:0]

200E[6:4]

R/W Connects dedicated I/O pins DIO2 and DIO4 through DIO11 as well

as input pins PB and OPT_RX/DIO1 to internal resources. If more

than one input is connected to the same resource, the ‘MULTIPLE’

column below specifies how they are combined.

DIO_Rx Resource MULTIPLE

000 NONE --

001 Reserved OR

010 T0 (Timer0 clock or gate) OR

011 T1 (Timer1 clock or gate) OR

100 High priority IO interrupt (int0 rising) OR

101 Low priority IO interrupt (int1 rising) OR

110 High priority IO interrupt (int0 falling) OR

111 Low priority IO interrupt (int1 falling) OR

DIO_DIR0[7:4,2:1] SFRA2

[7:4,2:0] 0 0 R/W Programs the direction of pins DIO7-DIO4 and DIO2-DIO1. 1 indi-

cates output. Ignored if the pin is not configured as I/O. See

DIO_PV and DIO_PW for special option for DIO6 and DIO7 outputs.

See DIO_EEX for special option for DIO4 and DIO5.

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Energy Meter IC

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DIO_DIR1[7:6,

3:0] SFR91

[7:6,3:0] 0 0 R/W Programs the direction of pins DIO15-DIO14, DIO11-DIO8. 1 indi-

cates output. Ignored if the pin is not configured as I/O.

DIO_DIR2

[5:3,2:1] SFRA1

[5:3,2:1]

0 0

R/W Programs the direction of pins DIO17-DIO16. 1 indicates output.

Ignored if the pin is not configured as I/O.

DIO_0[7:4,2:0]

SFR80

[7:4,2:0]

0 0

R/W The value on the pins DIO7-DIO4 and DIO2-DIO1. Pins configured

as LCD will read zero. When written, changes data on pins confi-

gured as outputs. Pins configured as LCD or input will ignore write

operations. The pushbutton input PB is read on DIO_0[0].

DIO_1[7:6,3:0]

SFR90

[7:6,3:0]

0 0

R/W The value on the pins DIO15-DIO14 and DIO11-DIO8. Pins con-

figured as LCD will read zero. When written, changes data on pins

configured as outputs. Pins configured as LCD or input will ignore

write operations.

DIO_2[5:3,1:0] SFRA0

[5:3,1:0]

0 0

R/W The value on the pins DIO17-DIO16. Pins configured as LCD will

read zero. When written, changes data on pins configured as out-

puts. Pins configured as LCD or input will ignore write operations.

DIO_EEX[1:0] 2008[7:6] 0 0 R/W

When set, converts DIO4 and DIO5 to interface with external

EEPROM. DIO4 becomes SDCK and DIO5 becomes bi-directional

SDATA. LCD_NUM must be less than or equal to 18.

DIO_EEX[1:0] Function

00 Disable EEPROM interface

01 2-Wire EEPROM interface

10 3-Wire EEPROM interface

11 --not used--

DIO_PW 2008[3] 0 0 R/W Causes WPULSE to be output on DIO6, if DIO6 is configured as

output. LCD_NUM must be less than 16.

EEDATA[7:0] SFR9E 0 0 R/W Serial EEPROM interface data

EECTRL[7:0] SFR9F 0 0 R/W Serial EEPROM interface control

ECK_DIS 2005[5] 0 0 R/W Emulator clock disable. When one, the emulator clock is disabled.

This bit is to be used with caution! Inadvertently

setting this bit will inhibit access to the part with the

ICE interface and thus preclude flash erase and pro-

gramming operations. If ECK_DIS is set to zero, it should be done

at least 1000ms after power-up to give emulators and programming

devices enough time to complete an erase operation.

EQU[2:0] 2000[7:5] 0 0 R/W Specifies the power equation to be used by the CE.

EX_XFR

Reserved

EX_FWCOL

EX_PLL

2002[0]

2001[1]

2007[4]

2007[5]

R/W Interrupt enable bits. These bits enable the XFER_BUSY, the

Firmware Collision, and PLL interrupts. Note that if one of these

interrupts is to be enabled, its corresponding 8051 EX enable must

also be set. See the Interrupts section for details. Note that bit

2001[1] must always be 0.

FIR_LEN 2005[4] 0 0 R/W The length of the ADC decimation FIR filter.

1-384 cycles, 0-288 cycles

When FIR_LEN=1, the ADC has 2.370370x higher gain.

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FLSH_ERASE[7:0] SFR94[7:0] 0 0 W Flash Erase Initiate

FLSH_ERASE is used to initiate either the Flash Mass Erase cycle or

the Flash Page Erase cycle. Specific patterns are expected for

FLSH_ERASE in order to initiate the appropriate Erase cycle.

(default = 0x00).

0x55 – Initiate Flash Page Erase cycle. Must be proceeded by a

write to FLSH_PGADR @ SFR 0xB7.

0xAA – Initiate Flash Mass Erase cycle. Must be proceeded by a

write to FLSH_MEEN @ SFR 0xB2 and the debug (CC)

port must be enabled.

Any other pattern written to FLSH_ERASE will have no effect.

FLSH_MEEN SFRB2[1] 0 0 W Mass Erase Enable

0 – Mass Erase disabled (default).

1 – Mass Erase enabled.

Must be re-written for each new Mass Erase cycle.

FLSH_PGADR[6:0] SFRB7[7:1] 0 0 W Flash Page Erase Address

FLSH_PGADR[6:0] – Flash Page Address (page 0 thru 127) that will

be erased during the Page Erase cycle. (default = 0x00).

Must be re-written for each new Page Erase cycle.

FLSH_PWE SFRB2[0] 0 0 R/W Program Write Enable

0 – MOVX commands refer to XRAM Space, normal operation

(default).

1 – MOVX @DPTR,A moves A to Program Space (Flash) @ DPTR.

This bit is automatically reset after each byte written to flash. Writes

to this bit are inhibited when interrupts are enabled.

FOVRIDE 20FD[4] 0 0 R/W Permits the values written by MPU to temporarily override the values

in the fuse register (reserved for production test).

IE_FWCOL0

IE_FWCOL1 SFRE8[2]

SFRE8[3]

R/W

Interrupt flags for Firmware Collision Interrupt. See Flash Memory

Section for details.

IE_PB SFRE8[4] 0 -- R/W PB flag. Indicates that a rising edge occurred on PB. Firmware must

write a zero to this bit to clear it. The bit is also cleared when MPU

requests SLEEP or LCD mode. On bootup, the MPU can read this

bit to determine if the part was woken with the PB DIO0[0].

IE_PLLRISE

SFRE8[6] 0 0 R/W Indicates that the MPU was woken or interrupted (int 4) by System

power becoming available, or more precisely, by PLL_OK rising.

Firmware must write a zero to this bit to clear it

IE_PLLFALL SFRE8[7] 0 0 R/W Indicates that the MPU has entered BROWNOUT mode because

System power has become unavailable (int 4), or more precisely,

because PLL_OK fell.

Note: this bit will not be set if the part wakes into

BROWNOUT mode because of PB or the WAKE timer.

Firmware must write a zero to this bit to clear it.

IE_XFER

SFRE8[0]

R/W Interrupt flag. This flag monitors the XFER_BUSY interrupt. The

flags is set by hardware and must be cleared by the interrupt

handler. Note that IE6, the interrupt 6 flag bit in the 8051 must also

be cleared when this interrupt occurs.

IE_WAKE SFRE8[5] 0 -- R/W Indicates that the MPU was woken by the autowake timer. This bit

is typically read by the MPU on bootup. Firmware must write a zero

to this bit to clear it

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INTBITS SFRF8[6:0] -- -- R/W Interrupt inputs. The MPU may read these bits to see the input to

external interrupts INT0, INT1, up to INT6. These bits do not have

any memory and are primarily intended for debug use.

LCD_BLKMAP19[3:0]

LCD_BLKMAP18[3:0]

205A[7:4]

205A[3:0]

0 -- R/W Identifies which segments connected to SEG18 and SEG19 should

blink. 1 means ‘blink.’ Most significant bit corresponds to COM3.

Least significant, to COM0.

LCD_CLK[1:0] 2021[1:0] 0 -- R/W Sets the LCD clock frequency (for COM/SEG pins, not frame rate).

Note: fw = 32768Hz

00: fw/29, 01: fw/28, 10: fw/27, 11: fw/26

LCD_E 2021[5] 0 -- R/W Enables the LCD display. When disabled, VLC2, VLC1, and VLC0

are ground as are the COM and SEG outputs.

LCD_MODE[2:0] 2021[4:2] 0 -- R/W The LCD bias mode.

000: 4 states, 1/3 bias

001: 3 states, 1/3 bias

010: 2 states, ½ bias

011: 3 states, ½ bias

100: static display

LCD_NUM[4:0] 2020[4:0] 0 -- R/W Number of dual-purpose LCD/DIO pins to be configured as LCD.

This will be a number between 0 and 18. The first dual-purpose pin

to be allocated as LCD is SEG37/DIO17 if LCD_NUM=5. If

LCD_NUM=6, SEG36 and SEG 37 will be configured as LCD. The

remaining SEG35 to SEG24 will be configured as DIO16 to DIO4.

DIO1 and DIO2 are always available, if not used for the optical port.

See tables in Application Section.

LCD_ONLY 20A9[5] 0 0 W Takes the device to LCD mode. Ignored if system power is present.

The part will awaken when autowake timer times out, when push

button is pushed, or when system power returns.

LCD_SEG0[3:0]

…

LCD_SEG19[3:0]

2030[3:0]

…

2043[3:0]

…

R/W

LCD_SEG24[3:0]

…

LCD_SEG38[3:0]

2048[3:0]

…

2056[3:0]

…

R/W

LCD Segment Data. Each word contains information for from 1 to 4

time divisions of each segment. In each word, bit 0 corresponds to

COM0, on up to bit 3 for COM3.

These bits are preserved in LCD and SLEEP modes,

even if their pin is not configured as SEG. In this case,

they can be useful as general-purpose non-volatile

storage.

LCD_Y 2021[6] 0 0 R/W LCD Blink Frequency (ignored if blink is disabled or if segment is

off).

0: 1Hz (500ms ON, 500ms OFF)

1: 0.5Hz (1s ON, 1s OFF)

MPU_DIV[2:0] 2004[2:0] 0 0 R/W The MPU clock divider (from 4.9152MHz). These bits may be pro-

grammed by the MPU without risk of losing control.

000-4.9152MHz, 001-4.9152MHz /21, …, 111-4.9152MHz /27

MPU_DIV remains unchanged when the part enters BROWNOUT

mode.

MUX_ALT 2005[2] 0 0 R/W The MPU asserts this bit when it wishes the MUX to perform ADC

conversions on an alternate set of inputs.

MUX_DIV[1:0] 2002[7:6] 0 0 R/W The number of states in the input multiplexer.

00- illegal

01- 4 states 10-3 states 11-2 states

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OPT_FDC[1:0] 2007[1:0] 0 0 R/W Selects OPT_TX modulation duty cycle

OPT_FDC Function

00 50% Low

01 25% Low

10 12.5% Low

11 6.25% Low

OPT_RXDIS 2008[5] 0 0 R/W OPT_RX can be configured as an analog input to the optical UART

comparator or as a digital input/output, DIO1.

0—OPT_RX, 1—DIO1.

OPT_RXINV 2008[4] 0 0 R/W Inverts result from OPT_RX comparator when 1. Affects only the

UART input. Has no effect when OPT_RX is used as a DIO input.

OPT_TXE[1,0] 2007[7,6] 00 00 R/W Configures the OPT_TX output pin.

00—OPT_TX, 01—DIO2, 10—WPULSE, 11—RESERVED

OPT_TXINV 2008[0] 0 0 R/W Invert OPT_TX when 1. This inversion occurs before modulation.

OPT_TXMOD 2008[1] 0 0 R/W Enables modulation of OPT_TX. When OPT_TXMOD is set,

OPT_TX is modulated when it would otherwise have been zero.

The modulation is applied after any inversion caused by

OPT_TXINV.

PLL_OK 2003[6] 0 0 R Indicates that system power is present and the clock generation PLL

is settled.

PLS_MAXWIDTH

[7:0] 2080[7:0] FF FF R/W Determines the maximum width of the pulse (low going pulse).

Maximum pulse width is (2*PLS_MAXWIDTH + 1)*TI. Where TI is

PLS_INTERVAL. If PLS_INTERVAL=0, TI is the sample time

(397µs). If 255, disable MAXWIDTH.

PLS_INTERVAL

[7:0] 2081[7:0] 0 0 R/W If the FIFO is used, PLS_INTERVAL must be set to 81. If

PLS_INTERVAL = 0, the FIFO is not used and pulses are output as

soon as the CE issues them.

PLS_INV 2004[6] 0 0 R/W Inverts the polarity of WPULSE. Normally, these pulses are active

low. When inverted, they become active high.

PREBOOT SFRB2[7] -- -- R Indicates that preboot sequence is active.

PRE_SAMPS[1:0] 2001[7:6] 0 0 R/W

The duration of the pre-summer, in samples.

00-42, 01-50, 10-84, 11-100.

RTM_E 2002[3] 0 0 R/W Real Time Monitor enable. When ‘0’, the RTM output is low. This bit

enables the two wire version of RTM

RTM0[7:0]

RTM1[7:0]

RTM2[7:0]

RTM3[7:0]

2060

2061

2062

2063

R/W Four RTM probes. Before each CE code pass, the values of these

registers are serially output on the RTM pin. The RTM registers are

ignored when RTM_E=0.

SECURE SFRB2[6] 0 -- R/W Enables security provisions that prevent external reading of flash

memory and CE program RAM. This bit is reset on chip reset and

may only be set. Attempts to write zero are ignored.

SLEEP 20A9[6] 0 0 W Takes the 6521BE to sleep mode. Ignored if system power is

present. The 6521BE will wake when the autowake timer times out,

when push button is pushed, or when system power returns.

SUM_CYCLES[5:0] 2001[5:0] 0 0 R/W The number of pre-summer outputs summed in the final summer.

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TMUX[4:0] 20AA[4:0] 2 -- R/W Selects one of 32 signals for TMUXOUT.

[4:0] Selected Signal [4:0] Selected Signal

0x00 DGND (analog) 0x01 Reserved

0x02 Reserved 0x03 Reserved

0x04 Reserved 0x05 Reserved

0x06 VBIAS (analog) 0x07 Not used

0x08 Reserved 0x09 Reserved

0x0A Reserved 0x0B

-0x13

Reserved

0x14 RTM (Real time

output from CE)

0x15 WDTR_E, comparator 1

Output AND V1LT3)

0x16 –

0x17

Not used 0x18 RXD, from optical in-

terface, after optional

inversion

0x19 MUX_SYNC 0x1A CK_10M

0x1B CK_MPU 0x1C Reserved

0x1D Reserved 0x1E CE_BUSY

0x1F XFER_BUSY

VERSION[7:0] 2006 -- -- R The version index. This word may be read by firmware to determine

the silicon version.

VERSION[7:0] Silicon Version

0000 0110 A06

VREF_CAL 2004[7] 0 0 R/W Brings VREF to VREF pad. This feature is disabled when

VREF_DIS=1.

VREF_DIS 2004[3] 0 1 R/W Disables the internal voltage reference.

WAKE_ARM 20A9[7] 0 -- W Arm the autowake timer. Writing a 1 to this bit arms the autowake

timer and presets it with the values presently in WAKE_PRD and

WAKE_RES. The autowake timer is reset and disarmed whenever

the processor is in MISSION mode or BROWNOUT mode. The

timer must be armed at least three crystal clock cycles before the

SLEEP or LCD-ONLY mode is commanded.

WAKE_PRD 20A9[2:0] 001 -- R/W Sleep time. Time=WAKE_PRD[2:0]*WAKE_RES. Default=001.

Maximum value is 7.

WAKE_RES 20A9[3] 0 -- R/W Resolution of WAKE timer: 1 – 1 minute, 0 – 2.5 seconds.

WD_RST SFRE8[7] 0 0 W WD timer bit: Possible operations to this bit are:

Read: Gets the status of the flag IE_PLLFALL

Write 0: Clears the flag

Write 1:.Resets the WDT

WD_OVF 2002[2] 0 0 R/W The WD overflow status bit. This bit is set when the WD timer

overflows. It is powered by the nonvolatile supply and at bootup will

indicate if the part is recovering from a WD overflow or a power fault.

This bit should be cleared by the MPU on bootup. It is also

automatically cleared when RESET is high.

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CE Interface Description

CE Program

The CE program is supplied by TERIDIAN as a data image that can be merged with the MPU operational code for meter

applications. Typically, the CE program covers most applications and does not need to be modified. The description in this

section applies to CE code revision CE6521BE_A04.

Formats

All CE words are 4 bytes. Unless specified otherwise, they are in 32-bit two’s complement (-1 = 0xFFFFFFFF). ‘Calibration’

parameters are defined in flash memory (or external EEPROM) and must be copied to CE data memory by the MPU before

enabling the CE. ‘Internal’ variables are used in internal CE calculations. ‘Input’ variables allow the MPU to control the behavior

of the CE code. ‘Output’ variables are outputs of the CE calculations.

Constants

Constants used in the CE Data Memory tables are:

 FS = 32768Hz/13 = 2520.62Hz.

 F0 is the fundamental frequency.

 IMAX is the external rms current corresponding to 250mV pk at the inputs IA and IB.

 VMAX is the external rms voltage corresponding to 250mV pk at the VA and VB inputs.

 NACC, the accumulation count for energy measurements is PRE_SAMPS*SUM_CYCLES.

 Accumulation count time for energy measurements is PRE_SAMPS*SUM_CYCLES/FS.

The system constants IMAX and VMAX are used to convert internal quantities (as used by the CE) to external, i.e. metering

quantities. Their values are determined by the off-chip scaling of the voltage and current sensors used in an actual meter. The

LSB values used in this document relate digital quantities at the CE interface to external meter input quantities. For example, if

a SAG threshold of 80V peak is desired at the meter input, the digital value that should be programmed into SAG_THR would

be 80V/SAG_THRLSB, where SAG_THRLSB is the LSB value in the description of SAG_THR.

The parameters EQU, CE_E, PRE_SAMPS, and SUM_CY CLES essential to the function of the CE are stored in I/O RAM (see I/O

RAM section).

Environment

Before starting the CE using the CE_E bit, the MPU has to establish the proper environment for the CE by implementing the

following steps:

 Load the CE data into CE DRAM.

 Establish the equation to be applied in EQU.

 Establish the accumulation period and number of samples in PRE_SAMPS and SUM_CYCLES.

 Establish the number of cycles per ADC mux frame.

 Set PLS_INTERVAL[7:0] to 81.

 Set FIR_LEN to 1 and MUX_DIV to 1.

There must be thirteen 32768Hz cycles per ADC mux frame (see System Timing Diagram, Figure 16). This means that the

product of the number of cycles per frame and the number of conversions per frame must be 12 (allowing for one settling

cycle). The required configuration is FIR_LEN = 1 (three cycles per conversion) and MUX_DIV = 1 (4 conversions per mux

frame).

During operation, the MPU is in charge of controlling the multiplexer cycles, for example by inserting an alternate multiplexer

sequence at regular intervals using MUX_ALT. This enables temperature measurement. The polarity of chopping circuitry must

be altered for each sample. It must also alternate for each alternate multiplexer reading. This is accomplished by maintaining

CHOP_E = 00.

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CE Calculations

The CE performs the precision computations necessary to accurately measure energy. These computations include offset

cancellation, products, product smoothing, product summation, frequency detection, and sag detection. All data computed by

the CE is dependent on the selected meter equation as given by EQU (in I/O RAM). However, for the 6521BE CE code, EQU is

always 0.

Element Input Mapping

EQU Watt Formula

(WSUM) W0SUM W1SUM I0SQSUM I1SQSUM

0 VA IA (1 element, 2W 1φ)

with tamper detection VA*IA VA*IB IA IB

CESTATUS

Since the CE_BUSY interrupt occurs at 2520.6Hz, it is desirable to minimize the computation required in the interrupt handler

of the MPU. The MPU can read the CE status word at every CE_BUSY interrupt.

Address Name Description

0x11E8 CESTATUS See description of CE status word below

The CE Status Word is used for generating early warnings to the MPU. It contains sag warnings for VA as well as the F0 bit, a

clock derived from the fundamental input frequency. CESTATUS provides information about the status of voltage and input AC

signal frequency, which are useful for generating early power fail warnings, e.g. to initiate necessary data storage. CESTATUS

represents the status flags for the preceding CE code pass (CE busy interrupt). Sag alarms are not remembered from one

code pass to the next. The CE Status word is refreshed at every CE_BUSY interrupt.

The significance of the bits in CESTATUS is shown in the table below:

CESTATUS

[bit] Name Description

31-29 Not Used These unused bits will always be zero.

28 F0

F0 is a square wave at the exact fundamental input frequency.

Mains Signal

27 CREEP Normally zero. Becomes one when creep logic has been applied to either WA or WB.

26 SAG_B

25 SAG_A

Normally zero. These bits come one when the voltage in the respective channel remains

below SAG_THR for SAG_CNT samples. Will not return to zero until the voltage rises above

SAG_THR.

24-0 Not Used These unused bits will always be zero.

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The CE is initialized by the MPU using CECONFIG (CESTATE). This register contains in packed form the control bits for

SAG_CNT, FREQSEL, NEUTRAL_TAMPER, IB_SHUNT, IA_SHUNT, PULSE_SLOW, and PULSE_FAST.

Address Name Default Description

0x1040 CECONFIG 0x5000 See description of CECONFIG below

The significance of the bits in CECONFIG is shown in the table below:

IA_SHUNT and/or IB_SHUNT can configure their respective current inputs to accept shunt resistor sensors. In this case the CE

provides an additional gain of 8 to the selected current input. WRATE may need to be adjusted based on the values of

IA_SHUNT and IB_SHUNT. Whenever IA_SHUNT or IB_SHUNT are set to 1, In_8 (in the equation for Kh) is assigned a value of

The CE pulse generator is controlled only by the CE (internal) variables.

Note: The 6521BE Demo Code creep function halts both internal and external pulse generation.

CECONFIG

[bit] Name Default Description

[15:8] SAG_CNT 80

(0x50)

Number of consecutive voltage samples below SAG_THR before a sag

alarm is declared. The maximum value is 255. SAG_THR is at address

0x14.

[7] -- 0 Reserved

[6] FREQSEL 0 Selected phase for frequency monitor (0 = A, 1 = B).

[5] NEUTRAL TAMPER 0 Alert CE that neutral line tampering has been detected.

[4] MAGNETIC TAMPER 0 Alert CE that magnetic tampering has been detected.

[3] IB_SHUNT 0 When 1, the current gain of channel B is increased by 8. The gain factor

controlled by In_SHUNT is referred to as In_8 throughout this document.

[2] IA_SHUNT 0 When 1, the current gain of channel A is increased by 8.

[1] PULSE_FAST 0

[0] PULSE_SLOW 0

When PULSE_SLOW = 1, the pulse generator input is reduced by a factor of

64. When PULSE_FAST = 1, the pulse generator input is increased 16x.

These two parameters control the pulse gain factor X (see table below).

Allowed values are either 1 or 0. Default is 0 (X = 6).

X PULSE_SLOW PULSE_FAST

1.5 * 22 = 6 0 0

1.5 * 26 = 96 0 1

1.5 * 2-4 = 0.09375 1 0

1.5 1 1

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CE TRANSFER VARIABLES

When the MPU receives the XFER_BUSY interrupt, it knows that fresh data is available in the transfer variables.

Fundamental Energy Measurement Variables

The table below describes each transfer variable for fundamental energy measurement. All variables are signed 32 bit

integers. Accumulated variables such as WSUM are internally scaled so they have at least 2x margin before overflow when the

integration time is 1 second. Additionally, the hardware will not permit output values to ‘fold back’ upon overflow.

Address Name Description

0x11D8 W0SUM_X

0x11C8 W1SUM_X

The sum of Watt samples from each wattmeter element (In_8 is the gain

configured by IA_SHUNT or IB_SHUNT).

LSB = 6.6952*10-13 VMAX IMAX / In_8 Wh.

WxSUM_X is the Wh value accumulated for element ‘X’ in the last accumulation interval and can be computed based on the

specified LSB value.

For example with VMAX = 600V and IMAX = 208A, LSB (for WxSUM_X) is 0.08356 µWh.

Instantaneous Energy Measurement Variables

The Frequency measurement is computed using the Frequency locked loop for the selected phase.

IxSQSUM_X and VxSQSUM are the squared current and voltage samples acquired during the last accumulation interval.

INSQSUM_X can be used for computing the neutral current.

Address Name Description

0x11E4 FREQ_X Fundamental frequency. LSB 6

32 10587.0

−

⋅≈≡ S

FHz

0x11F0 MAINEDGE_X The number of zero crossings of the selected voltage in the previous ac-

cumulation interval. Zero crossings are either direction and are de-

bounced.

0x11DC I0SQSUM_X

0x11CC I1SQSUM_X

The sum of squared current samples from each element.

LSB = 6.6952*10-13 IMAX2 / In_82 A2h

0x11E0 V0SQSUM_X

0x11D0 V1SQSUM_X

The sum of squared voltage samples from each element.

LSB= 6.6952*10-13 VMAX2 V2h

0x11F4 WSUM_ACCUM Rollover accumulator for WPULSE.

0x11D4 I0SQRT_X

0x11C4 I1SQRT_X

RMS current determined by calculating the square root of I0SQSUM_X

and I1SQSUM_X

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Other CE Parameters

Temperature Parameters

MAINEDGE_X is useful for implementing a real-time clock based on the input AC signal. MAINEDGE_X is the number of half-

cycles accounted for in the last accumulated interval for the AC signal.

TEMP_RAW may be used by the MPU to monitor chip temperature. Temperature compensation is implemented by the CE,

based on the value written to TEMP_NOM.

Address Name Default Description

0x11EC TEMP_RAW_X N/A Filtered, unscaled reading from the temperature sensor.

0x105C TEMP_NOM N/A Reference temperature for temperature compensation.

0x1054 DEGSCALE 19065 Multiplier for temperature calculation.

0x1048 GAIN_ADJ 16384 Scales all voltage and current inputs, based on the temperature

compensation mechanism. 16384 provides unity gain.

0x1080 PPMC1 N/A Linear parameter for temperature compensation.

0x1084 PPMC2 N/A Quadratic parameter for temperature compensation.

GAIN_ADJ is a scaling factor for measurements based on the temperature. GAIN_ADJ is controlled by the MPU for

temperature compensation.

Sag, Creep and Tamper Control

Address Name Default Description

0x1070 CREEP0_THR 8311

0x1074 CREEP1_THR 8311

Wh threshold for channels A and B.

ACC

VMAXIMAXLSB ⋅⋅⋅= −13

106952.6

The default value is equivalent to 2.5W

0x1050 SAG_THR 443000 The threshold for sag warnings. The default value is equivalent to 80V RMS

if VMAX = 600V. The LSB value is 1.80587*10-4V (RMS).

0x1078 VNOMINAL 1.27*108 Nominal voltage to be applied to the larger of the two currents when neutral

tampering is detected. The default value is equivalent to 230V RMS.

0x107C WNOMINAL 7646227

Nominal power consumption to be applied when magnetic tampering is

detected.

ACC

VMAXIMAXLSB ⋅⋅⋅= −13

106952.6

The default value is equivalent to 0.65Wh per accumulation interval, or

2300Wh/h (230V, 10A).

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Pulse Generation

Address Name Default Description

0x1044 WRATE 389

Kh = VMAX*IMAX*47.1132 / (In_8*WRATE*NACC*X) Wh/pulse. The default

value results in a Kh of 1.0Wh/pulse when 2520 samples are taken in each

accumulation interval (and VMAX=600, IMAX = 208, In_8 = 1, X = 6).

The maximum value for WRATE is 215 – 1.

WRATE controls the number of pulses that are generated per measured Wh quantities. The lower WRATE is the slower the

pulse rate for measured energy quantity. The metering constant Kh is derived from WRATE as the amount of energy measured

for each pulse. That is, if Kh = 1Wh/pulse, a power applied to the meter of 120V and 30A results in one pulse per second. If

the load is 240V at 150A, ten pulses per second will be generated. X is controlled by the PULSE_FAST and PULSE_SLOW bits

in the CECONFIG register.

The maximum pulse rate is 7.5kHz. The maximum time jitter is 67µs and is independent of the number of pulses measured.

Thus, if the pulse generator is monitored for 1 second, the peak jitter is 67ppm. After 10 seconds, the peak jitter is 6.7ppm.

The average jitter is always zero. If it is attempted to drive either pulse generator faster than its maximum rate, it will simply

output at its maximum rate without exhibiting any rollover characteristics. The actual pulse rate, using WSUM as an example,

is:

XFWSUMWRATE

RATE S

⋅⋅⋅

where FS = sampling frequency (2520.6Hz), X = Pulse speed factor

CE Calibration Parameters

The table below lists the parameters that are typically entered to effect calibration of meter accuracy.

Address Name Default Description

0x1020 CAL_IA 16384

0x1024 CAL_VA 16384

0x1028 CAL_IB 16384

0x102C CAL_VB 16384

These constants control the gain of their respective channels. The nominal

value for each parameter is 214 = 16384. The gain of each channel is directly

proportional to its CAL parameter. Thus, if the gain of a channel is 1% slow,

CAL should be scaled by 1/(1 – 0.01).

0x1030 PHADJ_A 0

0x1034 PHADJ_B 0

These two constants control the CT phase compensation. No compensation

occurs when PHADJ_X = 0. As PHADJ_X is increased, more compensation

(lag) is introduced. Range: ±215 – 1. If it is desired to delay the current by the

angle Φ:

Φ⋅−

⋅

=TAN

TAN

XPHADJ 0131.01487.0 02229.0

2_ 20 at 60Hz

⋅

−

⋅

=TA

TAN

XPHADJ 009695.01241.0 0155.0

2_ 20 at 50Hz

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Other CE Parameters

The table below shows CE parameters used for suppression of noise due to scaling and truncation effects.

Address Name Default Description

0x104C QUANTA 0

This parameter is added to the Watt calculation for element 0 to compensate

for input noise and truncation.

LSB = (VMAX*IMAX / In_8) *7.4162*10-10 W

0x1060 QUANTB 0

This parameter is added to the Watt calculation for element 1 to compensate

for input noise and truncation.

LSB = (VMAX*IMAX / In_8) *7.4162*10-10 W

0x1058 QUANT_IA 0

This parameter is added to compensate for input noise and truncation in the

squaring calculations for I2. QUANT_IA affects only I0SQSUM and I1SQSUM.

LSB = (IMAX2/In_82)*7.4162*10-10 A2

0x106C QUANT_IB 0

This parameter is added to compensate for input noise and truncation in the

squaring calculations for I2. QUANT_IB affects only I0SQSUM and I1SQSUM.

LSB = (IMAX2/In_82)*7.4162*10-10 A2

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ELECTRICAL SPECIFICATIONS

ABSOLUTE MAXIMUM RATINGS

Supplies and Ground Pins:

V3P3SYS, V3P3A −0.5V to 4.6V

VBAT -0.5V to 4.6V

GNDD -0.5V to +0.5V

Analog Output Pins:

V3P3D -10mA to 10mA,

-0.5V to 4.6V

VREF -10mA to +10mA,

-0.5V to V3P3A+0.5V

V2P5 -10mA to +10mA,

-0.5V to 3.0V

Analog Input Pins:

IA, VA, IB, VB, V1 -10mA to +10mA

-0.5V to V3P3A+0.5V

XIN, XOUT -10mA to +10mA

-0.5V to 3.0V

All Other Pins:

Configured as SEG or COM drivers -1mA to +1mA,

-0.5 to V3P3D+0.5

Configured as Digital Inputs -10mA to +10mA,

-0.5 to 6V

Configured as Digital Outputs -15mA to +15mA,

-0.5V to V3P3D+0.5V

All other pins −0.5V to V3P3D+0.5V

Operating junction temperature (peak, 100ms) 140 °C

Operating junction temperature (continuous) 125 °C

Storage temperature −45 °C to +165 °C

Solder temperature – 10 second duration 250 °C

ESD stress on all pins 4kV

Stresses beyond Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only and functional

operation at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure

to absolute-maximum-rated conditions for extended periods may affect device reliability. All voltages are with respect to GNDA.

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RECOMMENDED EXTERNAL COMPONENTS

NAME FROM TO FUNCTION VALUE UNIT

C1 V3P3A AGND

Bypass capacitor for 3.3V supply ≥0.1±20% μF

C2 V3P3D DGND

Bypass capacitor for 3.3V output 0.1±20% μF

CSYS V3P3SYS DGND Bypass capacitor for V3P3SYS ≥1.0±30% μF

C2P5 V2P5 DGND

Bypass capacitor for V2P5 0.1±20% μF

XTAL XIN XOUT

32.768kHz crystal – electrically similar to ECS

.327-12.5-17X or Vishay XT26T, load capaci-

tance 12.5pF

32.768 kHz

CXS † XIN AGND

Load capacitor for crystal (depends on crystal

specs and board parasitics). 27±10% pF

CXL † XOUT AGND

Load capacitor for crystal (depends on

crystal specs and board parasitics). 27±10% pF

† Depending on trace capacitance, higher or lower values for CXS and CXL must be used. Capacitance from XIN to GNDD

and XOUT to GNDD (combining pin, trace and crystal capacitance) should be 30pF to 42pF.

RECOMMENDED OPERATING CONDITIONS

PARAMETER CONDITION MIN TYP MAX UNIT

Normal Operation 3.0 3.3 3.6 V

3.3V Supply Voltage (V3P3SYS, V3P3A)

V3P3A and V3P3SYS must be at the

same voltage

Battery Backup 0 3.6 V

No Battery Externally Connect to V3P3SYS

VBAT Battery Backup

BRN and LCD modes

SLEEP mode

3.0

2.0

3.8

Operating Temperature -40 +85 ºC

Maximum input voltage on DIO/SEG pins

configured as DIO input. *

MISSION mode

BROWNOUT mode

LCD mode

V3P3SYS+0.3

VBAT+0.3

*Exceeding this limit will distort the LCD waveforms on other pins.

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PERFORMANCE SPECIFICATIONS

INPUT LOGIC LEVELS

PARAMETER CONDITION MIN TYP MAX UNIT

Digital high-level input voltage†, VIH 2 V

Digital low-level input voltage†, VIL 0.8 V

Exceptions to above input standard:

Input pull-up current, IIL

E_RXTX,

E_RST, CKTEST

Other digital inputs

VIN=0V, ICE_E=1

-1

100

µA

Input pull down current, IIH

ICE_E

Other digital inputs

VIN=V3P3D

-1

100

µA

†In battery powered modes, digital inputs should be below 0.3V or above 2.5V to minimize battery current.

OUTPUT LOGIC LEVELS

PARAMETER CONDITION MIN TYP MAX UNIT

ILOAD = 1mA V3P3D

–0.4 V

Digital high-level output voltage VOH

ILOAD = 15mA V3P3D-

0.6 V

ILOAD = 1mA 0 0.4 V

Digital low-level output voltage VOL ILOAD = 15mA 0.8 V

OPT_TX VOH (V3P3D-OPT_TX) ISOURCE=1mA 0.4 V

OPT_TX VOL ISINK=20mA 0.7 V

POWER-FAULT COMPARATOR

PARAMETER CONDITION MIN TYP MAX UNIT

Offset Voltage

V1-VBIAS

-20

+15

Hysteresis Current

V1 Vin = VBIAS - 100mV

0.8

1.2

μA

Response Time

V1 +100mV overdrive 2 5 10 μs

WDT Disable Threshold (V1-V3P3A) -400 -10 mV

BATTERY MONITOR

BME=1

PARAMETER CONDITION MIN TYP MAX UNIT

Load Resistor 27 45 63 kΩ

LSB Value - does not include the 9-

bit left shift at CE input.

FIR_LEN=0

FIR_LEN=1

-6.0

-2.6

-5.4

-2.3

-4.9

-2.0

μV

Offset Error -200 -72 +100 mV

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

SUPPLY CURRENT

PARAMETER CONDITION MIN TYP MAX UNIT

V3P3A + V3P3SYS current 6.1 7.7 mA

VBAT current

Normal Operation,

V3P3A=V3P3SYS=3.3V

MPU_DIV = 3 (614kHz), CKOUT_E =

0, CE_EN = 1, RTM_E = 0, ECK_DIS =

1, ADC_E = 1, ICE_E = 0 -300 +300 nA

V3P3A + V3P3SYS current vs.

MPU clock frequency Same conditions as above 0.5 mA/

MHz

V3P3A + V3P3SYS current,

Write Flash

Normal Operation as above, except

write Flash at maximum rate, CE_E=0,

ADC_E=0

9.1 10 mA

VBAT current

VBAT=3.6V

BROWNOUT mode, <25°C

BROWNOUT mode, >25°C

LCD Mode, 25°C

LCD mode, over temperature

SLEEP Mode, 25°C

Sleep mode, over temperature

5.7

2.9

120

150

8.5

5.0

µA

†Current into V3P3A and V3P3SYS pins is not zero if voltage is applied at these pins in brownout, LCD or sleep modes.

V3P3D SWITCH

PARAMETER CONDITION MIN TYP MAX UNIT

On resistance – V3P3SYS to V3P3D | IV3P3D | ≤ 1mA 10 Ω

On resistance – VBAT to V3P3D | IV3P3D | ≤ 1mA 40 Ω

2.5V VOLTAGE REGULATOR

Unless otherwise specified, load = 5mA

PARAMETER CONDITION MIN TYP MAX UNIT

Voltage overhead V3P3-V2P5 Reduce V3P3 until V2P5

drops 200mV 440 mV

PSSR ΔV2P5/ΔV3P3 RESET=0, iload=0 -3 +3 mV/V

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

LOW POWER VOLTAGE REGULATOR

Unless otherwise specified, V3P3SYS=V3P3A=0, PB=GND (BROWNOUT)

PARAMETER CONDITION MIN TYP MAX UNIT

V2P5 ILOAD=0 2.0 2.5 2.7 V

V2P5 load regulation ILOAD=0mA to 1mA 30 mV

VBAT voltage requirement

ILOAD=1mA,

Reduce VBAT until

REG_LP_OK=0

3.0 V

PSRR ΔV2P5/ΔVBAT ILOAD=0 -50 50 mV/V

CRYSTAL OSCILLATOR

PARAMETER CONDITION MIN TYP MAX UNIT

Maximum Output Power to Crystal Crystal connected 1 μW

XIN to XOUT Capacitance 3 pF

Capacitance to DGND

XIN

XOUT

VREF, VBIAS

Unless otherwise specified, VREF_DIS=0

PARAMETER CONDITION MIN TYP MAX UNIT

VREF output voltage, VNOM(25) Ta = 22ºC 1.193 1.195 1.197 V

VREF chop step 50 mV

VREF output impedance VREF_CAL =1,

ILOAD = 10µA, -10µA 2.5 kΩ

VNOM definitionA 2)22(1)22()22()( 2TCTTCTVREFTVNOM −+−+= V

VREF temperature coefficients

TC1

TC2

+7.0

-0.341

µV/ºC

µV/°C2

VREF aging

±25 ppm/year

VREF(T) deviation from VNOM(T)

)()( 6

VNOM TVNOMTVREF − Ta = -40ºC to +85ºC -40 +40 ppm/ºC

VBIAS voltage Ta = 25ºC

Ta = -40ºC to 85ºC

(-1%)

(-4%)

1.6

(+1%)

(+4%)

A This relationship describes the nominal behavior of VREF at different temperatures.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

LCD DRIVERS

Applies to all COM and SEG pins.

PARAMETER CONDITION MIN TYP MAX UNIT

VLC2 Max Voltage With respect to VLCD -0.1 0+.1 V

VLC1 Voltage,

1/3 bias

½ bias

With respect to 2*VLC2/3

With respect to VLC2/2

-4

-3

VLC0 Voltage,

1/3 bias

½ bias

With respect to VLC2/3

With respect to VLC2/2

-3

VLCD is V3P3SYS in MISSION mode and VBAT in BROWNOUT and LCD modes.

ADC CONVERTER, V3P3A REFERENCED

FIR_LEN=0, VREF_DIS=0, LSB values do not include the 9-bit left shift at CE input.

PARAMETER CONDITION MIN TYP MAX UNIT

Recommended Input Range

(Vin-V3P3A) -250 250

peak

Voltage to Current Crosstalk:

)cos(

*106VcrosstalkVin

Vin

Vcrosstalk ∠−∠

Vin = 200mV peak, 65Hz,

on VA

Vcrosstalk = largest

measurement on IA or IB

-10 10 μV/V

THD (First 10 harmonics)

250mV-pk

20mV-pk

Vin=65Hz,

64kpts FFT, Blackman-

Harris window

-75

-90

Input Impedance Vin=65Hz 40 90 kΩ

Temperature coefficient of Input

Impedance Vin=65Hz 1.7 Ω/°C

LSB size FIR_LEN=0

FIR_LEN=1 357

151 nV/LSB

Digital Full Scale FIR_LEN=0

FIR_LEN=1 +884736

±2097152 LSB

ADC Gain Error vs

%Power Supply Variation

3.3/33100 /357106

APV VnVNout INPK

Vin=200mV pk, 65Hz

V3P3A=3.0V, 3.6V 50 ppm/%

Input Offset (Vin-V3P3A) -10 10 mV

OPTICAL INTERFACE

PARAMETER CONDITION MIN TYP MAX UNIT

OPT_TX VOH (V3P3D-OPT_TX) ISOURCE=1mA 0.4 V

OPT_TX VOL ISINK=20mA 0.7 V

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

TEMPERATURE SENSOR

LSB values do not include the 9-bit left shift at CE input.

PARAMETER CONDITION MIN TYP MAX UNIT

Nominal Sensitivity (Sn)4 FIR_LEN=1 -2180 LSB/ºC

Nominal Sensitivity (Sn)4 FIR_LEN=0 -923 LSB/ºC

Nominal (Nn) 4, FIR_LEN=1 1.0 106 LSB

Nominal (Nn) 4, FIR_LEN=0

Tn=25ºC

Nominal relationship:

N(T)= Sn*(T-Tn)+Nn 0.4 106

LSB

Temperature Error††

⎟

⎠

⎞

⎜

⎝

⎛+

−

−= n

SNTN

TERR ))((

T = -40ºC to +85ºC,

Tn = 25°C

-10 +10 ºC

†† Nn is measured at Tn during meter calibration and is stored in MPU or CE for use in temperature calculations.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

TIMING SPECIFICATIONS

RAM AND FLASH MEMORY

PARAMETER CONDITION MIN TYP MAX UNIT

CKMPU = 4.9MHz 5 Cycles

CKMPU = 1.25MHz 2 Cycles

CE DRAM wait states

CKMPU = 614kHz 1 Cycles

Flash Read Pulse Width V3P3A=V3P3SYS=0

BROWNOUT MODE 30

100 ns

Flash write cycles -40°C to +85°C 20,000 Cycles

Flash data retention 25°C 100 Years

Flash data retention 85°C 10 Years

Flash byte writes between page or mass

erase operations 2 Cycles

FLASH MEMORY TIMING

PARAMETER CONDITION MIN TYP MAX UNIT

Write Time per Byte 42 µs

Page Erase (512 bytes) 20 ms

Mass Erase 200 ms

EEPROM INTERFACE

PARAMETER CONDITION MIN TYP MAX UNIT

CKMPU=4.9MHz, Using

interrupts 78 kHz

Write Clock frequency (I2C) CKMPU=4.9MHz, “bit-

banging” DIO4/5 150 kHz

Write Clock frequency (3-wire)

CKMPU=4.9MHz 500 kHz

RESET

PARAMETER CONDITION MIN TYP MAX UNIT

Reset pulse width 5 µs

Reset pulse fall time 1 µs

FOOTNOTES

1This spec is guaranteed, has been verified in production samples, but is not measured in production.

2This spec is guaranteed, has been verified in production samples, but is measured in production only at DC.

3This spec is measured in production at the limits of the specified operating temperature.

4This spec defines a nominal relationship rather than a measured parameter. Correct circuit operation is verified with

other specs that use this nominal relationship as a reference.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

TYPICAL PERFORMANCE DATA

-0.5

-0.4

-0.3

-0.2

-0.1

0.1

0.2

0.3

0.4

0.5

0.1 1 10 100 1000

Current [A]

Error [%]

Phase_0

Phase_60

Phase_300

Figure 38: Wh Accuracy, 0.1A to 200A at 240V/50Hz and Room Temperature

-8

-7

-6

-5

-4

-3

-2

-1

135791113151719212325

Harmonic

Error [%

]

50Hz Harmonic Data 60Hz Harmonic Data

Measured at current distortion amplitude of 40% and voltage distortion amplitude of 10%.

Figure 39: Meter Accuracy over Harmonics at 240V, 30A

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

Relative Accuracy over Temperature

-30

-20

-10

-60 -40 -20 0 20 40 60 80 100

Temperature [°C]

Accuracy [PPM/°C]

Figure 40: Typical Meter Accuracy over Temperature Relative to 25°C

PACKAGE OUTLINE (LQFP 64)

11.7

12.3

0.60 Typ.

1.40

1.60

11.7

12.3

0.00

0.20

9.8

10.2

0.50 Typ. 0.14

0.28

PIN No. 1 Indicator

Controlling dimensions are in mm

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

PINOUT (LQFP-64)

TERIDIAN

71M6521BE-IGT

GNDD

E_RXTX/SEG38

OPT_TX/DIO2

TMUXOUT

SEG3

V3P3D

CKTEST/SEG19

V3P3SYS

SEG4

SEG5

SEG37/DIO17

COM1

COM0

COM2

RESET

V2P5

VBAT

SEG31/DIO11

SEG30/DIO10

SEG29/DIO9

SEG28/DIO8

SEG27/DIO7

SEG26/DIO6

SEG25/DIO5

ICE_E

SEG24/DIO4

SEG18

SEG17

SEG16

COM3

SEG0

SEG35/DIO15

SEG36/DIO16

SEG6

SEG8

SEG1

SEG2

SEG34/DIO14

SEG7

SEG12

SEG10

SEG11

SEG9

SEG15

SEG13

SEG14

E_TCLK/SEG33

OPT_RX/DIO1

TEST

GNDA

V3P3A

E_RST/SEG32

XOUT

XIN

X4MHZ

VREF

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

PIN DESCRIPTIONS

Power/Ground Pins:

Name Type Circuit Description

GNDA P -- Analog ground: This pin should be connected directly to the ground plane.

GNDD P -- Digital ground: This pin should be connected directly to the ground plane.

V3P3A P -- Analog power supply: A 3.3V power supply should be connected to this pin, must be the

same voltage as V3P3SYS.

V3P3SYS P -- System 3.3V supply. This pin should be connected to a 3.3V power supply.

V3P3D O 13

Auxiliary voltage output of the chip, controlled by the internal 3.3V selection switch. In

mission mode, this pin is internally connected to V3P3SYS. In BROWNOUT mode, it is

internally connected to VBAT. This pin is floating in LCD and sleep mode.

VBAT P 12

Battery backup power supply. A battery or super-capacitor is to be connected between

VBAT and GNDD. If no battery is used, connect VBAT to V3P3SYS.

V2P5 O 10

Output of the internal 2.5V regulator. A 0.1µF capacitor to GNDA should be connected to

this pin.

Analog Pins:

Name Type Circuit Description

IA, IB I 6

Line Current Sense Inputs: These pins are voltage inputs to the internal A/D converter.

Typically, they are connected to the outputs of current sensors. Unused pins must be

connected to V3P3A.

VA, VB I 6

Line Voltage Sense Inputs: These pins are voltage inputs to the internal A/D converter.

Typically, they are connected to the outputs of resistor dividers. Unused pins must be

connected to V3P3A or tied to the voltage sense input that is in use.

V1 I 7

Comparator Input: This pin is a voltage input to the internal comparator. The voltage ap-

plied to the pin is compared to an internal BIAS voltage (1.6V). If the input voltage is

above the reference, the comparator output will be high (1). If the comparator output is

low, a voltage fault will occur. A 0.1µF capacitor to GNDA should be connected to this pin.

VREF O 9

Voltage Reference for the ADC. This pin is normally disabled by setting the VREF_CAL bit

in the I/O RAM and can be left unconnected. If enabled, a 0.1µF capacitor to GNDA

should be connected.

XIN

XOUT I 8

Crystal Inputs: A 32kHz crystal should be connected across these pins. Typically, a 27pF

capacitor is also connected from each pin to GNDA. It is important to minimize the

capacitance between these pins. See the crystal manufacturer datasheet for details.

Pin types: P = Power, O = Output, I = Input, I/O = Input/Output

The circuit number denotes the equivalent circuit, as specified under “I/O Equivalent Circuits”.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

Digital Pins:

Name Type Circuit Description

COM3, COM2,

COM1, COM0 O 5 LCD Common Outputs: These 4 pins provide the select signals for the LCD display.

SEG0…SEG18 O 5 Dedicated LCD Segment Output.

SEG24/DIO4…

SEG31/DIO11 I/O 3, 4, 5

Multi-use pins, configurable as either LCD SEG driver or DIO. (DIO4 = SCK, DIO5 =

SDA when configured as EEPROM interface, WPULSE = DIO6 when configured as

pulse outputs). If unused, these pins must be configured as outputs.

SEG34/DIO14…

SEG37/DIO17 I/O 3, 4, 5 Multi-use pins, configurable as either LCD SEG driver or DIO. If unused, these

pins must be configured as outputs.

E_RXTX/SEG38 I/O 1, 4, 5

E_RST/SEG32 I/O 1, 4, 5

E_TCLK/SEG33 O 4, 5

Multi-use pins, configurable as either emulator port pins (when ICE_E pulled high) or

LCD SEG drivers (when ICE_E tied to GND).

ICE_E I 2

ICE enable. When zero, E_RST, E_TCLK, and E_RXTX become SEG32, SEG33,

and SEG38 respectively. For production units, this pin should be pulled to GND to

disable the emulator port. This pin should be brought out to the programming inter-

face in order to create a way for reprogramming parts that have the SECURE bit set.

CKTEST/SEG19 O 4, 5

Multi-use pin, configurable as either Clock PLL output or LCD segment driver. Can

be enabled and disabled by CKOUT_EN.

TMUXOUT O 4

Digital output test multiplexer. Controlled by TMUX[4:0].

OPT_RX/DIO1 I/O 3, 4, 7

Multi-use pin, configurable as either Optical Receive Input or general DIO. When

configured as OPT_RX, this pin receives a signal from an external photo-detector

used in an IR serial interface. If unused, this pin must be configured as an

output or terminated to V3P3D or GNDD.

OPT_TX/DIO2 I/O 3, 4

Multi-use pin, configurable as either Optical LED Transmit Output, WPULSE,

RPULSE, or general DIO. When configured as OPT_TX, this pin is capable of

directly driving an LED for transmitting data in an IR serial interface. If unused, this

pin must be configured as an output or terminated to V3P3D or GNDD.

RESET I 3

This input pin resets the chip into a known state. For normal operation, this pin is

connected to GNDD. To reset the chip, this pin should be pulled high. No external

reset circuitry is necessary.

RX I 3

UART input. If unused, this pin must be terminated to V3P3D or GNDD.

TX O 4 UART output.

TEST I 7

Enables Production Test. Must be grounded in normal operation.

PB I 3

Push button input. A rising edge sets the IE_PB flag and causes the part to wake up

if it is in SLEEP or LCD mode. PB does not have an internal pull-up or pull-down. If

unused, this pin must be terminated to GNDD.

X4MHZ I 3

This pin must be connected to GNDD.

Pin types: P = Power, O = Output, I = Input, I/O = Input/Output

The circuit number denotes the equivalent circuit, as specified on the following page.

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

I/O Equivalent Circuits:

Digital Input Equivalent Circuit

Type 1:

Standard Digital Input or

pin configured as DIO Input

with Internal Pull-Up

GNDD

110K

V3P3D

CMOS

Input

V3P3D

Digital

Input

CMOS

Output

GNDD

V3P3D

GNDD

V3P3D

Digital Output Equivalent Circuit

Type 4:

Standard Digital Output or

pin configured as DIO Output

Digital

Output

LCD Output Equivalent Circuit

Type 5:

LCD SEG or

pin configured as LCD SEG

LCD

Driver

GNDD

LCD SEG

Output

MUX

GNDA

V3P3A

Analog Input Equivalent Circuit

Type 6:

ADC Input

Analog

Input

Comparator Input Equivalent

Circuit Type 7:

Comparator Input

GNDA

V3P3A

Comparator

Input

VREF Equivalent Circuit

Type 9:

VREF

from

internal

reference

GNDA

V3P3A

VREF

V2P5 Equivalent Circuit

Type 10:

V2P5

from

internal

reference

GNDD

V3P3D

V2P5

VBAT Equivalent Circuit

Type 12:

VBAT Power

GNDD

Power

Down

Circuits

VBAT

V3P3D Equivalent Circuit

Type 13:

V3P3D

from

V3P3SYS

V3P3D

from

VBAT

Oscillator Equivalent Circuit

Type 8:

Oscillator I/O

Oscillator

GNDD

Oscillator

Digital Input

Type 2:

Pin configured as DIO Input

with Internal Pull-Down

GNDD

110K

GNDD

CMOS

Input

V3P3D

Digital

Input

Digital Input Type 3:

Standard Digital Input or

pin configured as DIO Input

GNDD

CMOS

Input

V3P3D

Digital

Input

71M6521BE

Energy Meter IC

DATA SHEET

JANUARY 2008

ORDERING INFORMATION

PART PART DESCRIPTION

(PACKAGE, ACCURACY)

FLASH

MEMORY

SIZE

Packaging ORDERING

NUMBER

PACKAGE

MARKING

71M6521BE 64-pin LQFP, Lead Free, 0.5% 8KB Bulk 71M6521BE-IGT/F 71M6521BE-IGT

71M6521BE 64-pin LQFP, Lead Free, 0.5% 8KB Tape &

Reel

71M6521BE-

IGTR/F 71M6521BE-IGT

Data Sheet: This Data Sheet is proprietary to TERIDIAN Semiconductor Corporation (TSC) and sets forth design goals for the described

product. This data sheet is subject to change. TSC assumes no obligation regarding future manufacture, unless agreed to in writing. If and

when manufactured and sold, this product is sold subject to the terms and conditions of sale supplied at the time of order acknowledgment,

including those pertaining to warranty, patent infringement and limitation of liability. TERIDIAN Semiconductor Corporation (TSC) reserves

the right to make changes in specifications at any time without notice. Accordingly, the reader is cautioned to verify that a data sheet is

current before placing orders. TSC assumes no liability for applications assistance.

TERIDIAN Semiconductor Corp., 6440 Oak Canyon, Suite 100, Irvine, CA 92618

TEL (714) 508-8800, FAX (714) 508-8877, http://www.teridian.com