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FM31276/FM31278
64-Kbit/256-Kbit Integrated Processor
Companion with F-RAM
Cypress Semiconductor Corporation • 198 Champion Court • San Jose,CA 95134-1709 • 408-943-2600
Document Number: 001-86393 Rev. *F Revised November 19, 2018
64-Kbit/256-K bit Integrate d Processor C ompanion with F-RA M
Features
■64-Kbit/256-Kbit ferroelectric random access memory (F-RAM)
❐Logically organized as 8K × 8 (FM31276)/32K × 8 (FM31278)
❐High-endurance 100 trillion (1014) read/writes
❐151-year data retention (See Data Retention and Endurance
on page 28)
❐NoDelay™ writes
❐Advanced high-reliability ferroelectric process
■High Integration Device Replaces Multiple Parts
❐Serial nonvolatile memory
❐Real time clock (RTC)
❐Low voltage reset
❐Watchdog timer
❐Early power-fail warning/NMI
❐Two 16-bit event counter
❐Serial number with write-lock for security
■Real-time Clock/Calendar
❐Backup current at 2 V: 1.15 A at +25 C
❐Seconds through centuries in BCD format
❐Tracks leap years through 2099
❐Uses standard 32.768 kHz crystal (6 pF/12.5 pF)
❐Software calibration
❐Supports battery or capacitor backup
■Processor Companion
❐Active-low reset output for VDD and watchdog
❐Programmable low-VDD reset trip point
❐Manual reset filtered and debounced
❐Programmable watchdog timer
❐Dual Battery-backed event counter tracks system intrusions
or other events
❐Comparator for power-fail interrupt
❐64-bit programmable serial number with lock
■Fast 2-wire serial interface (I2C)
❐Up to 1-MHz frequency
❐Supports legacy timings for 100 kHz and 400 kHz
❐RTC, Supervisor controlled via I2C interface
❐Device select pins for up to 4 memory devices
■Low power consumption
❐1.5 mA active current at 1 MHz
❐150 A standby current
■Operating voltage: VDD = 4.0 V to 5.5 V
■Industrial temperature: –40 C to +85 C
■14-pin small outline integrated circuit (SOIC) package
■Restriction of hazardous substances (RoHS) compliant
■Underwriters laboratory (UL) recognized
Functional Description
The FM31276/FM31278 device integrates F-RAM memory with
the most commonly needed functions for processor-based
systems. Major features include nonvolatile memory, real time
clock, low-VDD reset, watchdog timer, nonvolatile event counter,
lockable 64-bit serial number area, and general purpose
comparator that can be used for a power-fail (NMI) interrupt or
any other purpose.
The FM31276/FM31278 is a 64-Kbit/256-Kbit nonvolatile
memory employing an advanced ferroelectric process. A
ferroelectric random access memory or F-RAM is nonvolatile
and performs reads and writes similar to a RAM. This memory is
truly nonvolatile rather than battery backed. It provides reliable
data retention for 151 years while eliminating the complexities,
overhead, and system-level reliability problems caused by other
nonvolatile memories. The FM31276/FM31278 is capable of
supporting 1014 read/write cycles, or 100 million times more write
cycles than EEPROM.
The real time clock (RTC) provides time and date information in
BCD format. It can be permanently powered from an external
backup voltage source, either a battery or a capacitor. The
timekeeper uses a common external 32.768 kHz crystal and
provides a calibration mode that allows software adjustment of
timekeeping accuracy.
The processor companion includes commonly needed CPU
support functions. Supervisory functions include a reset output
signal controlled by either a low VDD condition or a watchdog
timeout. RST goes active when VDD drops below a
programmable threshold and remains active for 100 ms after
VDD rises above the trip point. A programmable watchdog timer
runs from 100 ms to 3 seconds. The watchdog timer is optional,
but if enabled it will assert the reset signal for 100 ms if not
restarted by the host before the timeout. A flag-bit indicates the
source of the reset.
A comparator on PFI compares an external input pin to the
onboard 1.2 V reference. This is useful for generating a
power-fail interrupt (NMI) but can be used for any purpose. The
family also includes a programmable 64-bit serial number that
can be locked making it unalterable. Additionally it offers a dual
battery-backed event counter that tracks the number of rising or
falling edges detected on a dedicated input pin.
For a complete list of related documentation, click here.
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 2 of 36
Logic Block Diagram
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 3 of 36
Contents
Pinout ................................................................................4
Pin Definitions .................................................................. 4
Functional Overview ........................................................ 5
Memory Architecture ................................................... 5
Processor Companion ..................................................... 5
Processor Supervisor .................................................. 5
Manual Reset .............................................................. 6
Reset Flags ................................................................. 6
Early Power Fail Comparator ...................................... 6
Event Counter ............................................................. 7
Serial Number ............................................................. 7
Real-time Clock Operation ............................................... 7
Backup Power ............................................................. 8
Trickle Charger ............................................................ 8
Calibration ................................................................... 9
Crystal Oscillator ......................................................... 9
Layout Recommendations ............................................. 10
Register Map ................................................................... 13
I2C Interface .................................................................... 20
STOP Condition (P) ................................................... 20
START Condition (S) ................................................. 20
Data/Address Transfer .............................................. 20
Acknowledge/No-acknowledge ................................. 21
Slave Address ........................................................... 21
Addressing Overview - Memory ................................22
Addressing Overview - RTC & Companion ............... 22
Data Transfer ............................................................ 22
Memory Operation .......................................................... 23
Memory Write Operation ........................................... 23
Memory Read Operation ........................................... 24
RTC/Companion Write Operation ............................. 25
RTC/Companion Read Operation ............................. 25
Addressing FRAM Array
in the FM31276/FM31278 Family ..................................... 25
Maximum Ratings ........................................................... 26
Operating Range ............................................................. 26
DC Electrical Characteristics ........................................ 26
Data Retention and Endurance ..................................... 28
Capacitance .................................................................... 28
Thermal Resistance ........................................................ 28
AC Test Loads and Waveforms ..................................... 28
AC Test Conditions ........................................................ 28
Supervisor Timing .......................................................... 29
AC Switching Characteristics ....................................... 30
Ordering Information ...................................................... 31
Ordering Code Definitions ......................................... 31
Package Diagram ............................................................ 32
Acronyms ........................................................................ 33
Document Conventions ................................................. 33
Units of Measure ....................................................... 33
Document History Page ................................................. 34
Sales, Solutions, and Legal Information ...................... 36
Worldwide Sales and Design Support ....................... 36
Products .................................................................... 36
PSoC® Solutions ...................................................... 36
Cypress Developer Community ................................. 36
Technical Support ..................................................... 36
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 4 of 36
Pinout
Figure 1. 14-pin SOIC pinout
CNT1
CNT2
A0
A1
CAL/PFO
RST PFI
X1
X2
SDA
SCL
V
1
2
3
4
5
6
78
9
10
11
12
13
14
VSS
DD
VBAK
Pin Definitions
Pin Name I/O Type Description
A1–A0 Input Device Select Address 1–0. These pins are used to select one of up to 4 devices of the same type
on the same I2C bus. To select the device, the address value on the three pins must match the
corresponding bits contained in the slave address. The address pins are pulled down internally.
SDA Input/Output Serial Data/Address. This is a bi-directional pin for the I2C interface. It is open-drain and is intended
to be wire-OR'd with other devices on the I2C bus. The input buffer incorporates a Schmitt trigger for
noise immunity and the output driver includes slope control for falling edges. An external pull-up
resistor is required.
SCL Input Serial Clock. The serial clock pin for the I2C interface. Data is clocked out of the device on the falling
edge, and into the device on the rising edge. The SCL input also incorporates a Schmitt trigger input
for noise immunity.
CNT1, CNT2 Input Event Counter Inputs. These battery-backed inputs increment counters when an edge is detected
on the corresponding CNT pin. The polarity is programmable. These pins should not be left floating.
Tie to ground if these pins are not used.
X1, X2 Input/Output 32.768 kHz crystal connection. When using an external oscillator, apply the clock to X1 and a DC
mid-level to X2. These pins should be left unconnected if RTC is not used.
RST Input/Output Reset. This active-low output is open drain with weak pull-up. It is also an input when used as a manual
reset. This pin should be left floating if unused.
PFI Input Early Power-fail Input. Typically connected to an unregulated power supply to detect an early power
failure. This pin must be tied to ground if unused.
CAL/PFO Output Calibration/Early Power-fail Output. In calibration mode, this pin supplies a 512 Hz square-wave
output for clock calibration. In normal operation, this is the early power-fail output.
VBAK Power supply Backup supply voltage. Connected to a 3 V battery or a large value capacitor. If no backup supply
is used, this pin should be tied to ground and the VBC bit should be cleared in the RTC register 0Bh.
The trickle charger is UL recognized and ensures no excessive current when using a lithium battery.
VSS Power supply Ground for the device. Must be connected to the ground of the system.
VDD Power supply Power supply input to the device.
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 5 of 36
Functional Overview
The FM31276/FM31278 device combines a serial nonvolatile
RAM with a real time clock (RTC) and a processor companion.
The companion is a highly integrated peripheral including a
processor supervisor, a comparator used for early power-fail
warning, nonvolatile event counters, and a 64-bit serial number.
The FM31276/FM31278 integrates these complementary but
distinct functions under a common interface in a single package.
The product is organized as two logical devices. The first is a
memory and the second is the companion which includes all the
remaining functions. From the system perspective they appear
to be two separate devices with unique IDs on the serial bus.
The memory is organized as a standalone nonvolatile I2C
memory using standard device ID value. The real time clock and
supervisor functions are accessed with a separate I2C device ID.
This allows clock/calendar data to be read while maintaining the
most recently used memory address. The clock and supervisor
functions are controlled by 25 special function registers. The
RTC and event counter circuits are maintained by the power
source on the VBAK pin, allowing them to operate from battery or
backup capacitor power when VDD drops below a set threshold.
Each functional block is described below.
Memory Architecture
The FM31276/FM31278 device is available in memory size
64-Kbit/256-Kbit. The device uses two-byte addressing for the
memory portion of the chip. This makes the device software
compatible with its standalone memory counterparts, but makes
them compatible within the entire family.
The memory array is logically organized as 8,192 × 8 bits/
32,768 × 8 bits and is accessed using an industry-standard I2C
interface. The memory is based on F-RAM technology.
Therefore it can be treated as RAM and is read or written at the
speed of the I2C bus with no delays for write operations. It also
offers effectively unlimited write endurance unlike other
nonvolatile memory technologies. The I2C protocol is described
in I2C Interface on page 20.
The memory array can be write-protected by software. Two bits
in the processor companion area (WP1, WP0 in register 0Bh)
control the protection setting. Based on the setting, the protected
addresses cannot be written and the I2C interface will not
acknowledge any data to protected addresses. The special
function registers containing these bits are described in detail
below.
Processor Companion
In addition to nonvolatile RAM, the FM31276/FM31278
incorporates a real time clock and highly integrated processor
companion. The companion includes a low-VDD reset, a
programmable watchdog timer, a battery-backed event
counters, a comparator for early power-fail detection or other
purposes, and a 64-bit serial number.
Processor Supervisor
Supervisors provide a host processor two basic functions:
detection of power supply fault conditions and a watchdog timer
to escape a software lockup condition. The FM31276/FM31278
has a reset pin (RST) to drive a processor reset input during
power faults, power-up, and software lockups. It is an open drain
output with a weak internal pull-up to VDD. This allows other reset
sources to be wire-OR’d to the RST pin. When VDD is above the
programmed trip point, RST output is pulled weakly to VDD. If
VDD drops below the reset trip point voltage level (VTP), the RST
pin will be driven LOW. It will remain LOW until VDD falls too low
for circuit operation which is the VRST level. When VDD rises
again above VTP
, RST continues to drive LOW for at least 100
ms (tRPU) to ensure a robust system reset at a reliable VDD level.
After tRPU has been met, the RST pin will return to the weak
HIGH state. While RST is asserted, serial bus activity is locked
out even if a transaction occurred as VDD dropped below VTP
. A
memory operation started while VDD is above VTP will be
completed internally.
Tab l e 2 below shows how bit VTP controls the trip point of the
low-VDD reset. They are located in register 0Bh, bits 1 and 0. The
reset pin will drive LOW when VDD is below the selected VTP
voltage, and the I2C interface and F-RAM array will be locked
out. Note that the bit 1 location is a don’t care. Figure 2 illustrates
the reset operation in response to a low VDD.
A watchdog timer can also be used to drive an active reset signal.
The watchdog is a free-running programmable timer. The
timeout period can be software programmed from 100 ms to
3 seconds in 100 ms increments via a 5-bit nonvolatile register.
Table 1. Block Memory Write Protection
WP1 WP0 Protected Address Range
00 None
0 1 Bottom 1/4
1 0 Bottom 1/2
1 1 Full array
Table 2. VTP setting
VTP Setting VTP
3.9 V 0
4.4 V 1
Figure 2. Low VDD Reset
V
DD
V
TP
t
RPU
RST
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 6 of 36
All programmed settings are minimum values and vary with
temperature according to the operating specifications. The
watchdog has two additional controls associated with its
operation, a watchdog enable bit (WDE) and timer restart bits
(WR). Both the enable bit must be set and the watchdog must
timeout in order to drive RST active. If a reset event occurs, the
timer will automatically restart on the rising edge of the reset
pulse. If WDE = ‘0’, the watchdog timer runs but a watchdog fault
will not cause RST to be asserted LOW. The WTR flag will be
set, indicating a watchdog fault. This setting is useful during
software development if the developer does not want RST to
drive. Note that setting the maximum timeout setting (11111b)
disables the counter to save power. The second control is a
nibble that restarts the timer preventing a reset. The timer should
be restarted after changing the timeout value.
The watchdog timeout value is located in register 0Ah, bits 4:0,
and the watchdog enable is bit 7. The watchdog is restarted by
writing the pattern 1010b to the lower nibble of register 09h.
Writing this pattern will also cause the timer to load new timeout
values. Writing other patterns to this address will not affect its
operation. Note the watchdog timer is free-running. Prior to
enabling it, users should restart the timer as described above.
This assures that the full timeout period will be set immediately
after enabling. The watchdog is disabled when VDD is below VTP
.
The following table summarizes the watchdog bits. A block
diagram follows.
Manual Reset
The RST is a bi-directional signal allowing the
FM31276/FM31278 to filter and de-bounce a manual reset
switch. The RST input detects an external low condition and
responds by driving the RST signal LOW for 100 ms.
Note The internal weak pull-up eliminates the need for additional
external components.
Reset Flags
In case of a reset condition, a flag bit will be set to indicate the
source of the reset. A low-VDD reset is indicated by the POR flag,
register 09h bit 6. A watchdog reset is indicated by the WTR flag,
register 09h bit 7. Note that the flags are internally set in
response to reset sources, but they must be cleared by the user.
When the register is read, it is possible that both flags are set if
both have occurred since the user last cleared them.
Early Power Fail Comparator
An early power fail warning can be provided to the processor well
before VDD drops out of spec. The comparator is used to create
a power fail interrupt (NMI). This can be accomplished by
connecting the PFI pin to the unregulated power supply via a
resistor divider. An application circuit is shown below.
Watchdog Timeout WDT(4:0) 0Ah, bits 4:0
Watchdog Enable WDE 0Ah, bit 7
Watchdog Restart WR(3:0) 09h, bits 3:0
Figure 3. Watchdog Timer
Timebase Down Counte
r
Watchdog
Timer Settings
100 m
clock
WDE
RST
WR
(
3:0
)
= 1010b to restart
Figure 4. Manual Reset
Figure 5. Comparator as a Power-Fail Warning
FM31276/FM31278
Reset
Switch
RST
MCU
RST FM312 76/FM31
278
drives
100 ms
(
min.
)
+
-1.2 V ref
Re
g
ulator
V
DD
FM31276/
FM31278
CAL/PFO
PFI
To MCU
NMI in
p
ut
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 7 of 36
The voltage on the PFI input pin is compared to an onboard 1.2 V
reference. When the PFI input voltage drops below this
threshold, the comparator will drive the CAL/PFO pin to a LOW
state. The comparator has 100 mV (max) of hysteresis to reduce
noise sensitivity, only for a rising PFI signal. For a falling PFI
edge, there is no hysteresis.
The comparator is a general purpose device and its application
is not limited to the NMI function.
The comparator is not integrated into the special function
registers except as it shares its output pin with the CAL output.
When the RTC calibration mode is invoked by setting the CAL
bit (register 00h, bit 2), the CAL/PFO output pin will be driven with
a 512 Hz square wave and the comparator will be ignored. Since
most users only invoke the calibration mode during production,
this should have no impact on system operations using the
comparator.
Note The maximum voltage on the comparator input PFI is
limited to 3.75 V under normal operating conditions.
Event Counter
The FM31276/FM31278 offers the user two battery-backed
event counters. Input pins CNT1 and CNT2 are programmable
edge detectors. Each clocks a 16-bit counter. When an edge
occurs, the counters will increment their respective registers.
Counter 1 is located in registers 0Dh and 0Eh, Counter 2 is
located in registers 0Fh and 10h. These register values can be
read anytime VDD is above VTP, and they will be incremented as
long as a valid VBAK power source is provided. To read, set the
RC bit, register 0Ch bit 3 to 1. This takes a snapshot of all four
counter bytes allowing a stable value even if a count occurs
during the read. The registers can be written by software allowing
the counters to be cleared or initialized by the system. Counts
are blocked during a write operation. The two counters can be
cascaded to create a single 32-bit counter by setting the CC
control bit (register 0Ch, bit 2). When cascaded, the CNT1 input
will cause the counter to increment. CNT2 is not used in this
mode and should be tied to ground.
The control bits for event counting are located in register 0Ch.
Counter 1 Polarity is bit C1P, bit 0; Counter 2 Polarity is C2P, bit
1; the Cascade Control is CC, bit 2; and the Read Counter bit is
RC, bit 3.
The polarity bits must be set prior to setting the counter value(s).
If a polarity bit is changed, the counter may inadvertently
increment. If the counter pins are not being used, tie them to
ground.
Serial Number
A memory location to write a 64-bit serial number is provided. It
is a writeable nonvolatile memory block that can be locked by the
user once the serial number is set. The 8 bytes of data and the
lock bit are all accessed via the device ID for the Processor
Companion. Therefore the serial number area is separate and
distinct from the memory array. The serial number registers can
be written an unlimited number of times, so these locations are
general purpose memory. However, once the lock bit is set, the
values cannot be altered and the lock cannot be removed. Once
locked the serial number registers can still be read by the
system.
The serial number is located in registers 11h to 18h. The lock bit
is SNL (register 0Bh, bit 7). Setting the SNL bit to a ‘1’ disables
writes to the serial number registers, and the SNL bit cannot be
cleared.
Real-time Clock Operation
The real-time clock (RTC) is a timekeeping device that can be
battery or capacitor backed for permanently-powered operation.
It offers a software calibration feature that allows high accuracy.
The RTC consists of an oscillator, clock divider, and a register
system for user access. It divides down the 32.768 kHz
time-base and provides a minimum resolution of seconds (1 Hz).
Static registers provide the user with read/write access to the
time values. It includes registers for seconds, minutes, hours,
day-of-the-week, date, months, and years. A block diagram
(Figure 7 on page 8) illustrates the RTC function.
The user registers are synchronized with the timekeeper core
using R and W bits in register 00h described below. Changing
the R bit from ‘0’ to ‘1’ transfers timekeeping information from the
core into holding registers that can be read by the user. If a
timekeeper update is pending when R is set, then the core will
be updated prior to loading the user registers. The registers are
frozen and will not be updated again until the R bit is cleared to
‘0’. R is used for reading the time.
Setting the W bit to ‘1’ locks the user registers. Clearing it to ‘0’
causes the values in the user registers to be loaded into the
timekeeper core. W bit is used for writing new time values. Users
should be certain not to load invalid values, such as FFh, to the
timekeeping registers. Updates to the timekeeping core occur
continuously except when locked.
Figure 6. Event Counter
16-
bit Count er
CNT1
CC
CNT2
C1P
C2P
16-
bit Count er
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 8 of 36
Backup Power
The real-time clock/calendar is intended to be permanently
powered. When the primary system power fails, the voltage on
the VDD pin will drop. When VDD is less than 2.5 V, the RTC (and
event counters) will switch to the backup power supply on VBAK.
The clock operates at extremely low current in order to maximize
battery or capacitor life. However, an advantage of combining a
clock function with F-RAM memory is that data is not lost
regardless of the backup power source.
The IBAK current varies with temperature and voltage (see DC
Electrical Characteristics on page 26). The following graph
shows IBAK as a function of VBAK. These curves are useful for
calculating backup time when a capacitor is used as the VBAK
source.
The minimum VBAK voltage varies linearly with temperature. The
user can expect the minimum VBAK voltage to be 1.23 V at
+85 °C and 1.90 V at -40 °C. The tested limit is 1.55 V at +25 °C.
Note The minimum VBAK voltage has been characterized at
-40 °C and +85 °C but is not 100% tested.
Trickle Charger
To facilitate capacitor backup the VBAK pin can optionally provide
a trickle charge current. When the VBC bit (register 0Bh, bit 2) is
set to ‘1’, the VBAK pin will source approximately 80 µA until VBAK
reaches 3.75 V. In 5 V systems, this charges the capacitor to VDD
without an external diode and resistor charger and also prevents
the user from exceeding the VBAK maximum voltage
specification. There is a Fast Charge mode which is enabled by
the FC bit (register 0Bh, bit 5). In this mode the trickle charger
current is set to approximately 1 mA, allowing a large backup
capacitor to charge more quickly.
Figure 7. Real-time Clock Core Block Diagram
32.768 kHz
crystal
Oscillator Clock
Divider
Update
Logic
512 Hz or
Square Wave
Seconds
7 bits
MInutes
7 bits
Hours
6 bits
Date
6 bits
Months
5 bits
Years
8 bits
Days
3 bits
User Interface Registers
1 Hz
W
R
OSCEN
CF
Figure 8. IBAK vs. VBAK Voltage
IBAK (A)
VBAK (V)
Figure 9. VBAK(min.) vs Temperature
Temperature (°C)
VBAKmin. (V)
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 9 of 36
In the case where no battery is used, the VBAK pin should be tied
to VSS. VBAK should not be tied to 5 V since the VBAK (max)
specification will be exceeded. Be sure to turn off the trickle
charger (VBC = ‘0’), otherwise charger current will be shunted to
ground from VDD.
Note Systems using lithium batteries should clear the VBC bit to
‘0’ to prevent battery charging. The VBAK circuitry includes an
internal 1 K
series resistor as a safety element. The trickle
charger is UL Recognized.
Calibration
When the CAL bit in the register 00h is set to ‘1’, the clock enters
calibration mode. In calibration mode, the CAL/PFO output pin is
dedicated to the calibration function and the power fail output is
temporarily unavailable. Calibration operates by applying a
digital correction to the counter based on the frequency error. In
this mode, the CAL/PFO pin is driven with a 512 Hz (nominal)
square wave. Any measured deviation from 512 Hz translates
into a timekeeping error. The user converts the measured error
in ppm and writes the appropriate correction value to the
calibration register. The correction factors are listed in the table
below. Positive ppm errors require a negative adjustment that
removes pulses. Negative ppm errors require a positive
correction that adds pulses. Positive ppm adjustments have the
CALS (sign) bit set to ‘1’, whereas negative ppm adjustments
have CALS = ‘0’. After calibration, the clock will have a maximum
error of ±2.17 ppm or ±0.09 minutes per month at the calibrated
temperature.
The calibration setting is stored in F-RAM so it is not lost should
the backup source fail. It is accessed with bits CAL(4:0) in
register 01h. This value can be written only when the CAL bit is
set to a ‘1’. To exit the calibration mode, the user must clear the
CAL bit to a ‘0’. When the CAL bit is ‘0’, the CAL/PFO pin will
revert to the power fail output function.
Crystal Oscillator
The crystal oscillator is designed to use a 6 pF/12.5 pF crystal
without the need for external components, such as loading
capacitors. The FM31276/FM31278 device has built-in loading
capacitors that are optimized for use with 6 pF crystals, but which
work well with 12.5 pF crystals. For either crystal, no additional
external loading capacitors are required nor suggested.
If a 32.768 kHz crystal is not used, an external oscillator may be
connected to the FM31276/FM31278. Apply the oscillator to the
X1 pin. Its high and low voltage levels can be driven rail-to-rail or
amplitudes as low as approximately 500 mV p-p. To ensure
proper operation, a DC bias must be applied to the X2 pin. It
should be centered between the high and low levels on the X1
pin. This can be accomplished with a voltage divider.
In the example, R1 and R2 are chosen such that the X2 voltage
is centered around the X1 oscillator drive levels. If you wish to
avoid the DC current, you may choose to drive X1 with an
external clock and X2 with an inverted clock using a CMOS
inverter.
Figure 10. External Oscillator
FM31276/FM31278
VDD
R1
R2
X1 X2
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 10 of 36
Layout Recommendations
The X1 and X2 crystal pins employ very high impedance circuits
and the oscillator connected to these pins can be upset by noise
or extra loading. To reduce RTC clock errors from signal
switching noise, a guard ring must be placed around these pads
and the guard ring grounded. SDA and SCL traces should be
routed away from the X1 / X2 pads. The X1 and X2 trace lengths
should be less than 5 mm. The use of a ground plane on the
backside or inner board layer is preferred. See layout example.
Red is the top layer, green is the bottom layer.
Figure 11. Layout Recommendations
Layout for Surface Mount Crystal
(red = top layer, green = bottom layer)
Layout for Through Hole Crystal
(red = top layer, green = bottom layer)
VDD
SC L
SD A
X2
X1
PFI
VBAK
VDD
SC L
SDA
X2
X1
PFI
VBAK
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 11 of 36
Table 3. Digital Calibration Adjustments
S.No. Measured Frequency Range Error Range (PPM) Program Calibration Register to:
Min Max Min Max
Positive Calibration for slow clocks: Calibration will achieve ±2.17 PPM after calibration
0 512.0000 511.9989 0 2.17 000000
1 511.9989 511.9967 2.18 6.51 100001
2 511.9967 511.9944 6.52 10.85 100010
3 511.9944 511.9922 10.86 15.19 100011
4 511.9922 511.9900 15.20 19.53 100100
5 511.9900 511.9878 19.54 23.87 100101
6 511.9878 511.9856 23.88 28.21 100110
7 511.9856 511.9833 28.22 32.55 100111
8 511.9833 511.9811 32.56 36.89 101000
9 511.9811 511.9789 36.90 41.23 101001
10 511.9789 511.9767 41.24 45.57 101010
11 511.9767 511.9744 45.58 49.91 101011
12 511.9744 511.9722 49.92 54.25 101100
13 511.9722 511.9700 54.26 58.59 101101
14 511.9700 511.9678 58.60 62.93 101110
15 511.9678 511.9656 62.94 67.27 101111
16 511.9656 511.9633 67.28 71.61 110000
17 511.9633 511.9611 71.62 75.95 110001
18 511.9611 511.9589 75.96 80.29 110010
19 511.9589 511.9567 80.30 84.63 110011
20 511.9567 511.9544 84.64 88.97 110100
21 511.9544 511.9522 88.98 93.31 110101
22 511.9522 511.9500 93.32 97.65 110110
23 511.9500 511.9478 97.66 101.99 110111
24 511.9478 511.9456 102.00 106.33 111000
25 511.9456 511.9433 106.34 110.67 111001
26 511.9433 511.9411 110.68 115.01 111010
27 511.9411 511.9389 115.02 119.35 111011
28 511.9389 511.9367 119.36 123.69 111100
29 511.9367 511.9344 123.70 128.03 111101
30 511.9344 511.9322 128.04 132.37 111110
31 511.9322 511.9300 132.38 136.71 111111
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 12 of 36
Negative Calibration for fast clocks: Calibration will achieve ±2.17 PPM after calibration
0 512.0000 512.0011 0 2.17 000000
1 512.0011 512.0033 2.18 6.51 000001
2 512.0033 512.0056 6.52 10.85 000010
3 512.0056 512.0078 10.86 15.19 000011
4 512.0078 512.0100 15.20 19.53 000100
5 512.0100 512.0122 19.54 23.87 000101
6 512.0122 512.0144 23.88 28.21 000110
7 512.0144 512.0167 28.22 32.55 000111
8 512.0167 512.0189 32.56 36.89 001000
9 512.0189 512.0211 36.90 41.23 001001
10 512.0211 512.0233 41.24 45.57 001010
11 512.0233 512.0256 45.58 49.91 001011
12 512.0256 512.0278 49.92 54.25 001100
13 512.0278 512.0300 54.26 58.59 001101
14 512.0300 512.0322 58.60 62.93 001110
15 512.0322 512.0344 62.94 67.27 001111
16 512.0344 512.0367 67.28 71.61 010000
17 512.0367 512.0389 71.62 75.95 010001
18 512.0389 512.0411 75.96 80.29 010010
19 512.0411 512.0433 80.30 84.63 010011
20 512.0433 512.0456 84.64 88.97 010100
21 512.0456 512.0478 88.98 93.31 010101
22 512.0478 512.0500 93.32 97.65 010110
23 512.0500 512.0522 97.66 101.99 010111
24 512.0522 512.0544 102.00 106.33 011000
25 512.0544 512.0567 106.34 110.67 011001
26 512.0567 512.0589 110.68 115.01 011010
27 512.0589 512.0611 115.02 119.35 011011
28 512.0611 512.0633 119.36 123.69 011100
29 512.0633 512.0656 123.70 128.03 011101
30 512.0656 512.0678 128.04 132.37 011110
31 512.0678 512.0700 132.38 136.71 011111
Table 3. Digital Calibration Adjustments (continued)
S.No. Measured Frequency Range Error Range (PPM) Program Calibration Register to:
Min Max Min Max
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 13 of 36
Register Map
The RTC and processor companion functions are accessed via 25 special function registers, which are mapped to a separate I2C
device ID. The interface protocol is described on I2C Interface on page 20. The registers contain timekeeping data, control bits, and
information flags. A description of each register follows the summary table.
Note When the device is first powered up and programmed, all timekeeping registers must be written because the battery-backed
register values cannot be guaranteed. The table below shows the default values of the non-volatile registers. All other register values
should be treated as unknown.
Table 4. Register Map Summary Table
Address Data Function Range
D7 D6 D5 D4 D3 D2 D1 D0
18h Serial Number Byte 7 Serial Number 7 FFh
17h Serial Number Byte 6 Serial Number 6 FFh
16h Serial Number Byte 5 Serial Number 5 FFh
15h Serial Number Byte 4 Serial Number 4 FFh
14h Serial Number Byte 3 Serial Number 3 FFh
13h Serial Number Byte 2 Serial Number 2 FFh
12h Serial Number Byte 1 Serial Number 1 FFh
11h Serial Number Byte 0 Serial Number 0 FFh
10h Counter 2 MSB Event Counter 2 MSB FFh
0Fh Counter 2 LSB Event Counter 2 LSB FFh
0Eh Counter 1 MSB Event Counter 1 MSB FFh
0Dh Counter 1 LSB Event Counter 1 LSB FFh
0Ch RC CC C2P C1P Event Count Control
0Bh SNL – FC WP1 WP0 VBC – VTP Companion Control
0Ah WDE – – WDT4 WDT3 WDT2 WDT1 WDT0 Watchdog Control
09h WTR POR LB – WR3 WR2 WR1 WR0 Watchdog Restart/Flags
08h 10 years years Years 00–99
07h 0 0 0 10
months
months Month 01–12
06h 0 0 10 date date Date 01–31
05h00000 day Day 01–07
04h 0 0 10 hours hours Hours 00–23
03h 0 10 minutes minutes Minutes 00–59
02h 0 10 seconds seconds Seconds 00–59
01h OSCEN reserved CALS CAL4 CAL3 CAL2 CAL1 CAL0 CAL Control
00h reserved CF reserved reserved reserved CAL WRRTC Control
Nonvolatile = Battery-backed =
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 14 of 36
Table 5. Default Register Values
Address Hex Value Address Hex Value
18h 0x00 0Ah 0x1F
17h 0x00 08h 0x00
16h 0x00 07h 0x01
15h 0x00 06h 0x01
14h 0x00 05h 0x01
13h 0x00 04h 0x00
12h 0x00 03h 0x01
11h 0x00 02h 0x00
0Bh 0x00 01h 0x80
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 15 of 36
Table 6. Register Description
Address Description
18h Serial Number Byte 7
D7 D6 D5 D4 D3 D2 D1 D0
SN.63 SN.62 SN.61 SN.60 SN.59 SN.58 SN.57 SN.56
Upper byte of the serial number. Read/write when SNL = ‘0’, read-only when SNL = ‘1’. Nonvolatile.
17h Serial Number Byte 6
D7 D6 D5 D4 D3 D2 D1 D0
SN.55 SN.54 SN.53 SN.52 SN.51 SN.50 SN.49 SN.48
16h Byte 6 of the serial number. Read/write when SNL = ‘0’, read-only when SNL = ‘1’. Nonvolatile.
Serial Number Byte 5
D7 D6 D5 D4 D3 D2 D1 D0
SN.47 SN.46 SN.45 SN.44 SN.43 SN.42 SN.41 SN.40
Byte 5 of the serial number. Read/write when SNL = ‘0’, read-only when SNL = ‘1’. Nonvolatile.
15h Serial Number Byte 4
D7 D6 D5 D4 D3 D2 D1 D0
SN.39 SN.38 SN.37 SN.36 SN.35 SN.34 SN.33 SN.32
Byte 4 of the serial number. Read/write when SNL = ‘0’, read-only when SNL = ‘1’. Nonvolatile.
14h Serial Number Byte 3
D7 D6 D5 D4 D3 D2 D1 D0
SN.31 SN.30 SN.29 SN.28 SN.27 SN.26 SN.25 SN.24
Byte 3 of the serial number. Read/write when SNL = ‘0’, read-only when SNL = ‘1’. Nonvolatile.
13h Serial Number Byte 2
D7 D6 D5 D4 D3 D2 D1 D0
SN.23 SN.22 SN.21 SN.20 SN.19 SN.18 SN.17 SN.16
Byte 2 of the serial number. Read/write when SNL = ‘0’, read-only when SNL = ‘1’. Nonvolatile.
12h Serial Number Byte 1
D7 D6 D5 D4 D3 D2 D1 D0
SN.15 SN.14 SN.13 SN.12 SN.11 SN.10 SN.9 SN.8
Byte 1 of the serial number. Read/write when SNL = ‘0’, read-only when SNL = ‘1’. Nonvolatile.
11h Serial Number Byte 0
D7 D6 D5 D4 D3 D2 D1 D0
SN.7 SN.6 SN.5 SN.4 SN.3 SN.2 SN.1 SN.0
LSB of the serial number. Read/write when SNL = ‘0’, read-only when SNL = ‘1’. Nonvolatile.
10h Counter 2 MSB
D7 D6 D5 D4 D3 D2 D1 D0
C2.15 C2.14 C2.13 C2.12 C2.11 C2.10 C2.9 C2.8
Event Counter 2 MSB. Increments on overflows from Counter 2 LSB. Battery-backed, read/write.
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 16 of 36
0Fh Counter 2 LSB
D7 D6 D5 D4 D3 D2 D1 D0
C2.7 C2.6 C2.5 C2.4 C2.3 C2.2 C2.1 C2.0
Event Counter 2 LSB. Increments on programmed edge event on CNT2 input or overflows from Counter 1 MSB when
CC = ‘1’. Battery-backed, read/write.
0Eh Counter 1 MSB
D7 D6 D5 D4 D3 D2 D1 D0
C1.15 C1.14 C1.13 C1.12 C1.11 C1.10 C1.9 C1.8
Event Counter 1MSB. Increments on overflows from Counter 1 LSB. Battery-backed, read/write.
0Dh Counter 1 LSB
D7 D6 D5 D4 D3 D2 D1 D0
C1.7 C1.6 C1.5 C1.4 C1.3 C1.2 C1.1 C1.0
Event Counter 1 LSB. Increments on programmed edge event on CNT1 input. Battery-backed, read/write.
0Ch Event Counter Control
D7 D6 D5 D4 D3 D2 D1 D0
––––RCCC C2P C1P
RC Read Counter. Setting this bit to ‘1’ takes a snapshot of the four counters bytes allowing the system to read the values
without missing count events. The RC bit will be automatically cleared.
CC Counter Cascade. When CC = ‘0’, the event counters operate independently according to the edge programmed by
C1P and C2P respectively. When CC = ‘1’, the counters are cascaded to create one 32-bit counter. The registers of
Counter 2 represent the most significant 16-bits of the counter and CNT1 is the controlling input. Bit C2P is don’t care
when CC = ‘1’. Battery-backed, read/write.
C2P CNT2 detects falling edges when C2P = ‘0’, rising edges when C2P = ‘1’. C2P is “don't care” when CC = ‘1’. The
value of Event Counter 2 may inadvertently increment if C2P is changed. Battery-backed, read/write.
C1P CNT1 detects falling edges when C1P = ‘0’, rising edges when C1P = ‘1’. The value of Event Counter 1 may
inadvertently increment if C1P is changed. Battery-backed, read/write.
0Bh Companion Control
D7 D6 D5 D4 D3 D2 D1 D0
SNL – FC WP1 WP0 VBC – VTP
SNL Serial Number Lock: Setting to a ‘1’ makes registers 11h to 18h and SNL permanently read-only. SNL cannot be
cleared once set to ‘1’. Nonvolatile, read/write.
FC Fast Charge: Setting FC to '1' (and VBC = ‘1’) causes a ~1 mA trickle charge current to be supplied on VBAK. Clearing
VBC to '0' disables the charge current. Nonvolatile, read/write.
WP(1:0) Write Protect. These bits control the write protection of the memory array. Nonvolatile, read/write.
Write protect address WP1 WP0
None 0 0
Bottom 1/4 0 1
Bottom 1/2 1 0
Full array 1 1
VBC VBAK Charger Control. Setting VBC to ‘1’ (and FC = ‘0’) causes a 80 µA (1 mA if FC = ‘1’) trickle charge current to
be supplied on VBAK. Clearing VBC to ‘0’ disables the charge current. Nonvolatile, read/write.
Table 6. Register Description (continued)
Address Description
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 17 of 36
VTP VTP Select. This bit control the reset trip point for the low VDD reset function. Nonvolatile, read/write.
Trip Voltage VTP
3.9 V 0
4.4 V 1
0Ah Watchdog Control
D7 D6 D5 D4 D3 D2 D1 D0
WDE – – WDT4 WDT3 WDT2 WDT1 WDT0
WDE Watchdog Enable. When WDE = ‘1’, a watchdog timer fault will cause the RST signal to go active. When WDE = ‘0’
the timer runs but has no effect on RST
, however the WTR flag will be set when a fault occurs. Note as the timer is
free-running, users should restart the timer using WR(3:0) prior to setting WDE = ‘1’. This assures a full watchdog
timeout interval occurs. Nonvolatile, read/write.
WDT(4:0) Watchdog Timeout. Indicates the minimum watchdog timeout interval with 100 ms resolution. New watchdog timeouts
are loaded when the timer is restarted by writing the 1010b pattern to WR(3:0). Nonvolatile, read/write.
Watchdog Timeout WDT4 WDT3 WDT2 WDT1 WDT0
Invalid - default 100 ms 0 0 0 0 0
100 ms 0 0 0 0 1
200 ms 0 0 0 1 0
300 ms 0 0 0 1 1
.
.
2000 ms 1 0 1 0 0
2100 ms 1 0 1 0 1
2200 ms 1 0 1 1 0
.
.
2900 ms 1 1 1 0 1
3000 ms 1 1 1 1 0
Disable Counter 1 1 1 1 1
09h Watchdog Restart and Flags
D7 D6 D5 D4 D3 D2 D1 D0
WTR POR LB – WR3 WR2 WR1 WR0
WTR Watchdog Timer Reset Flag: When a watchdog timer fault occurs, the WTR bit will be set to ‘1’. It must be cleared
by the user. Note that both WTR and POR could be set if both reset sources have occurred since the flags were
cleared by the user. Battery-backed. Read/Write (internally set, user can clear bit).
POR Power-on Reset Flag: When the RST pin is activated by VDD < VTP
, the POR bit will be set to ‘1’. It must be cleared
by the user. Note that both WTR and POR could be set if both reset sources have occurred since the flags were
cleared by the user. Battery-backed. Read/Write (internally set, user can clear bit).
LB Low Backup Flag: On power up, if the VBAK source is below the minimum voltage to operate the RTC and event
counters, this bit will be set to ‘1’. The user should clear it to ‘0’ when initializing the system. Battery-backed.
Read/Write (internally set, user can clear bit).
WR(3:0) Watchdog Restart: Writing a pattern 1010b to WR(3:0) restarts the watchdog timer. The upper nibble contents do not
affect this operation. Writing any pattern other than 1010b to WR(3:0) has no effect on the timer. This allows users
to clear the WTR, POR, and LB flags without affecting the watchdog timer. Battery-backed, Write-only.
Table 6. Register Description (continued)
Address Description
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 18 of 36
08h Timekeeping – Years
D7 D6 D5 D4 D3 D2 D1 D0
10 year.3 10 year.2 10 year.1 10 year.0 Yea r. 3 Year.2 Year.1 Ye ar.0
Contains the lower two BCD digits of the year. Lower nibble contains the value for years; upper nibble contains the
value for 10s of years. Each nibble operates from 0 to 9. The range for the register is 0–99. Battery-backed, read/write.
07h Timekeeping – Months
D7 D6 D5 D4 D3 D2 D1 D0
00010 Month Month.3 Month.2 Month.1 Month.0
Contains the BCD digits for the month. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble
(one bit) contains the upper digit and operates from 0 to 1. The range for the register is 1–12. Battery-backed,
read/write.
06h Timekeeping – Date of the month
D7 D6 D5 D4 D3 D2 D1 D0
0010 date.1 10 date.0 Date.3 Date.2 Date.1 Date.0
Contains the BCD digits for the date of the month. Lower nibble contains the lower digit and operates from 0 to 9;
upper nibble contains the upper digit and operates from 0 to 3. The range for the register is 1–31. Battery-backed,
read/write.
05h Timekeeping – Day of the week
D7 D6 D5 D4 D3 D2 D1 D0
00000Day.2 Day.1 Day.0
Lower nibble contains a value that correlates to day of the week. Day of the week is a ring counter that counts from
1 to 7 then returns to 1. The user must assign meaning to the day value, as the day is not integrated with the date.
Battery-backed, read/write.
04h Timekeeping – Hours
D7 D6 D5 D4 D3 D2 D1 D0
0010 hours.1 10 hours.0 Hours.3 Hours.2 Hours.1 Hours.0
Contains the BCD value of hours in 24-hour format. Lower nibble contains the lower digit and operates from 0 to 9;
upper nibble (two bits) contains the upper digit and operates from 0 to 2. The range for the register is 0–23.
Battery-backed, read/write.
03h Timekeeping – Minutes
D7 D6 D5 D4 D3 D2 D1 D0
010 min.2 10 min.1 10 min.0 Min.3 Min.2 Min.1 Min.0
Contains the BCD value of minutes. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble
contains the upper minutes digit and operates from 0 to 5. The range for the register is 0-59. Battery-backed,
read/write.
Table 6. Register Description (continued)
Address Description
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 19 of 36
02h Timekeeping – Seconds
D7 D6 D5 D4 D3 D2 D1 D0
010 sec.2 10 sec.1 10 sec.0 Seconds.3 Seconds.2 Seconds.1 Seconds.0
Contains the BCD value of seconds. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble
contains the upper digit and operates from 0 to 5. The range for the register is 0–59. Battery-backed, read/write.
01h CAL/Control
D7 D6 D5 D4 D3 D2 D1 D0
OSCEN Reserved CALS CAL.4 CAL.3 CAL.2 CAL.1 CAL.0
OSCEN Oscillator Enable. When set to ‘1’, the oscillator is halted. When set to ‘0’, the oscillator runs after tOSC time. Disabling
the oscillator can save battery power during storage. On a power-up without battery, this bit is set to ‘1’.
Battery-backed, read/write.
Reserved Reserved bits. Do not use. Should remain set to ‘0’.
CALS Calibration Sign: Determines if the calibration adjustment is applied as an addition to or as a subtraction from the
time-base. This bit can be written only when CAL = ‘1’. Nonvolatile, read/write.
CAL(4:0) Calibration Setting: These five bits control the calibration of the clock. These bits can be written only when CAL = ‘1’.
Nonvolatile, read/write.
00h RTC Control
D7 D6 D5 D4 D3 D2 D1 D0
Reserved CF Reserved Reserved Reserved CAL W R
CF Century Overflow Flag. This bit is set to a ‘1’ when the values in the years register overflows from 99 to 00. This
indicates a new century, such as going from 1999 to 2000 or 2099 to 2100. The user should record the new century
information as needed. This bit is cleared to ‘0’ when the Flag register is read. It is read-only for the user.
Battery-backed.
CAL Calibration Setting. When set to ‘1’, the clock enters calibration mode. When CAL is set to ‘0’, the clock operates
normally, and the CAL/PFO pin is controlled by the power fail comparator. Battery-backed, read/write.
W Write Time. Setting the W bit to ‘1’ freezes the clock. The user can then write the timekeeping registers with updated
values. Resetting the W bit to ‘0’ causes the contents of the time registers to be transferred to the timekeeping counters
and restarts the clock. Battery-backed, read/write.
R Read Time. Setting the R bit to ‘1’ copies a static image of the timekeeping core and place it into the user registers.
The user can then read them without concerns over changing values causing system errors. The R bit going from ‘0’
to ‘1’ causes the timekeeping capture, so the bit must be returned to ‘0’ prior to reading again. Battery-backed,
read/write.
Reserved Reserved bits. Do not use. Should remain set to ‘0’.
Table 6. Register Description (continued)
Address Description
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 20 of 36
I2C Interface
The FM31276/FM31278 employs an industry standard I2C bus
that is familiar to many users. This product is unique since it
incorporates two logical devices in one chip. Each logical device
can be accessed individually. Although monolithic, it appears to
the system software to be two separate products. One is a
memory device. It has a Slave Address (Slave ID = 1010b) that
operates the same as a stand-alone memory device. The second
device is a real-time clock and processor companion which have
a unique Slave Address (Slave ID = 1101b).
By convention, any device that is sending data onto the bus is
the transmitter while the target device for this data is the receiver.
The device that is controlling the bus is the master. The master
is responsible for generating the clock signal for all operations.
Any device on the bus that is being controlled is a slave. The
FM31276/FM31278 is always a slave device.
The bus protocol is controlled by transition states in the SDA and
SCL signals. There are four conditions including START, STOP,
data bit, or acknowledge. Figure 12 and Figure 13 illustrates the
signal conditions that specify the four states. Detailed timing
diagrams are shown in the electrical specifications section.
STOP Condition (P)
A STOP condition is indicated when the bus master drives SDA
from LOW to HIGH while the SCL signal is HIGH. All operations
using the FM31276/FM31278 should end with a STOP condition.
If an operation is in progress when a STOP is asserted, the
operation will be aborted. The master must have control of SDA
in order to assert a STOP condition.
START Condition (S)
A START condition is indicated when the bus master drives SDA
from HIGH to LOW while the SCL signal is HIGH. All commands
should be preceded by a START condition. An operation in
progress can be aborted by asserting a START condition at any
time. Aborting an operation using the START condition will ready
the FM31276/FM31278 for a new operation.
If during operation the power supply drops below the specified
VTP minimum, any I2C transaction in progress will be aborted
and the system should issue a START condition prior to
performing another operation.
Data/Address Transfer
All data transfers (including addresses) take place while the SCL
signal is HIGH. Except under the three conditions described
above, the SDA signal should not change while SCL is HIGH.
Figure 12. START and STOP Conditions
full pagewidth
SDA
SCL
P
STOP Condition
SDA
SCL
S
START Condition
Figure 13. Data Transfer on the I2C Bus
handbook, full pagewidth
S
or
P
SDA
S
P
SCL
STOP or
START
condition
S
START
condition
2 3 4 - 8 9
ACK
9
ACK
78
12
MSB Acknowledgement
signal from slave
Byte complete
Acknowledgement
signal from receiver
1
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 21 of 36
Acknowledge/No-acknowledge
The acknowledge takes place after the 8th data bit has been
transferred in any transaction. During this state the transmitter
should release the SDA bus to allow the receiver to drive it. The
receiver drives the SDA signal LOW to acknowledge receipt of
the byte. If the receiver does not drive SDA LOW, the condition
is a no-acknowledge and the operation is aborted.
The receiver would fail to acknowledge for two distinct reasons.
First is that a byte transfer fails. In this case, the no-acknowledge
ceases the current operation so that the device can be
addressed again. This allows the last byte to be recovered in the
event of a communication error.
Second and most common, the receiver does not acknowledge
to deliberately end an operation. For example, during a read
operation, the FM31276/FM31278 will continue to place data
onto the bus as long as the receiver sends acknowledges (and
clocks). When a read operation is complete and no more data is
needed, the receiver must not acknowledge the last byte. If the
receiver acknowledges the last byte, this will cause the
FM31276/FM31278 to attempt to drive the bus on the next clock
while the master is sending a new command such as STOP.
Slave Address
The first byte that the FM31276/FM31278 expects after a START
condition is the slave address. As shown in Figure 15 and
Figure 16, the slave address contains the device type or slave
ID, the device select address bits, and a bit that specifies if the
transaction is a read or a write.
The FM31276/FM31278 has two Slave Addresses (Slave IDs)
associated with two logical devices. Bits 7–4 are the device type
(slave ID) and should be set to 1010b for the memory device.
The other logical device within the FM31276/FM31278 is the
real-time clock and companion. Bits 7–4 are the device type
(slave ID) and should be set to 1101b for the RTC and
companion. A bus transaction with this slave address will not
affect the memory in any way. The figures below illustrate the two
Slave Addresses.
Bits 2–1 are the device select address bits. They must match the
corresponding value on the external address pins to select the
device. Up to four FM31276/FM31278 devices can reside on the
same I2C bus by assigning a different address to each. Bit 0 is
the read/write bit (R/W). R/W = ‘1’ indicates a read operation and
R/W = ‘0’ indicates a write operation.
Figure 14. Acknowledge on the I2C Bus
handbook, full pagewidth
S
START
Condition
9821
Clock pulse for
acknowledgement
No Acknowledge
Acknowledge
DATA OUTPUT
BY MASTER
DATA OUTPUT
BY SLAVE
SCL FROM
MASTER
Figure 15. Memory Slave Device Address
Figure 16. Companion Slave Device Address
handbook, halfpage
R/W
LSBMSB
Slave ID
10 10 X A0A1
Device
Select
handbook, halfpage
R/W
LSBMSB
Slave ID
11 01 X A0A1
Device
Select
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 22 of 36
Addressing Overview - Memory
After the FM31276/FM31278 (as receiver) acknowledges the
slave address, the master can place the memory address on the
bus for a write operation. The address requires two bytes. The
complete 15-bit address is latched internally. Each access
causes the latched address value to be incremented
automatically. The current address is the value that is held in the
latch; either a newly written value or the address following the
last access. The current address will be held for as long
as VDD >V
TP or until a new value is written. Reads always use
the current address. A random read address can be loaded by
beginning a write operation as explained below.
After transmission of each data byte, just prior to the
acknowledge, the FM31276/FM31278 increments the internal
address latch. This allows the next sequential byte to be
accessed with no additional addressing. After the last address
(7FFFh) is reached, the address latch will roll over to 0000h.
There is no limit to the number of bytes that can be accessed
with a single read or write operation.
Addressing Overview - RTC & Companion
The RTC and Processor Companion operate in a similar manner
to the memory, except that it uses only one byte of address.
Addresses 00h to 18h correspond to special function registers.
Attempting to load addresses above 18h is an illegal condition;
the FM31276/FM31278 will return a NACK and abort the I2C
transaction.
Data Transfer
After the address bytes have been transmitted, data transfer
between the bus master and the FM31276/FM31278 can begin.
For a read operation the FM31276/FM31278 will place 8 data
bits on the bus then wait for an acknowledge from the master. If
the acknowledge occurs, the FM31276/FM31278 will transfer
the next sequential byte. If the acknowledge is not sent, the
FM31276/FM31278 will end the read operation. For a write
operation, the FM31276/FM31278 will accept 8 data bits from
the master then send an acknowledge. All data transfer occurs
MSB (most significant bit) first.
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 23 of 36
Memory Operation
The FM31276/FM31278 is designed to operate in a manner very
similar to other I2C interface memory products. The major
differences result from the higher performance write capability of
F-RAM technology. These improvements result in some
differences between the FM31276/FM31278 and a similar
configuration EEPROM during writes. The complete operation
for both writes and reads is explained below.
The memory address for FM31276 range from 0x0000 to
0x1FFFF, and for FM31278, they range from 0x0000 to 0x7FFF.
Memory functionality is described with respect to FM31278 in the
following sections.
Memory Write Operation
All writes begin with a slave address, then a memory address.
The bus master indicates a write operation by setting the LSB of
the slave address (R/W bit) to a ‘0’. After addressing, the bus
master sends each byte of data to the memory and the memory
generates an acknowledge condition. Any number of sequential
bytes may be written. If the end of the address range is reached
internally, the address counter will wrap from 7FFFh to 0000h.
Unlike other nonvolatile memory technologies, there is no
effective write delay with F-RAM. Since the read and write
access times of the underlying memory are the same, the user
experiences no delay through the bus. The entire memory cycle
occurs in less time than a single bus clock. Therefore, any
operation including read or write can occur immediately following
a write. Acknowledge polling, a technique used with EEPROMs
to determine if a write is complete is unnecessary and will always
return a ready condition.
Internally, an actual memory write occurs after the 8th data bit is
transferred. It will be complete before the acknowledge is sent.
Therefore, if the user desires to abort a write without altering the
memory contents, this should be done using START or STOP
condition prior to the 8th data bit. The FM31276/FM31278 uses
no page buffering.
Figure 17 and Figure 18 below illustrate a single-byte and
multiple-byte write cycles.
Figure 17. Single-Byte Write
S ASlave Address 0Address MSB AData Byte A P
By Master
By F-RAM
Start Address & Data Stop
Acknowledge
Address LSB A
Figure 18. Multi-Byte Write
S ASlave Address 0Address MSB AData Byte A P
By Master
By F-RAM
Start
Address & Data Stop
Acknowledge
Address LSB AData Byte A
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 24 of 36
Memory Read Operation
There are two basic types of read operations. They are current
address read and selective address read. In a current address
read, the FM31276/FM31278 uses the internal address latch to
supply the address. In a selective read, the user performs a
procedure to set the address to a specific value.
Current Address & Sequential Read
As mentioned above the FM31276/FM31278 uses an internal
latch to supply the address for a read operation. A current
address read uses the existing value in the address latch as a
starting place for the read operation. The system reads from the
address immediately following that of the last operation.
To perform a current address read, the bus master supplies a
slave address with the LSB set to a ‘1’. This indicates that a read
operation is requested. After receiving the complete slave
address, the FM31276/FM31278 will begin shifting out data from
the current address on the next clock. The current address is the
value held in the internal address latch.
Beginning with the current address, the bus master can read any
number of bytes. Thus, a sequential read is simply a current
address read with multiple byte transfers. After each byte the
internal address counter will be incremented.
Note Each time the bus master acknowledges a byte, this
indicates that the FM31276/FM31278 should read out the next
sequential byte.
There are four ways to properly terminate a read operation.
Failing to properly terminate the read will most likely create a bus
contention as the FM31276/FM31278 attempts to read out
additional data onto the bus. The four valid methods are:
1. The bus master issues a no-acknowledge in the 9th clock
cycle and a STOP in the 10th clock cycle. This is illustrated in
the diagrams below. This is preferred.
2. The bus master issues a no-acknowledge in the 9th clock
cycle and a START in the 10th.
3. The bus master issues a STOP in the 9th clock cycle.
4. The bus master issues a START in the 9th clock cycle.
If the internal address reaches 7FFFh, it will wrap around to
0000h on the next read cycle. Figure 19 and Figure 20 below
show the proper operation for current address reads.
Figure 19. Current Address Read
S ASlave Address 1Data Byte 1 P
By Master
By F-RAM
Start Address
Stop
Acknowledge
No
Acknowledge
Data
Figure 20. Sequential Read
S ASlave Address 1Data Byte 1 P
By Master
By F-RAM
Start Address
Stop
Acknowledge
No
Acknowledge
Data
Data ByteA
Acknowledge
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 25 of 36
Selective (Random) Read
There is a simple technique that allows a user to select a random
address location as the starting point for a read operation. This
involves using the first three bytes of a write operation to set the
internal address followed by subsequent read operations.
To perform a selective read, the bus master sends out the slave
address with the LSB (R/W) set to ‘0’. This specifies a write
operation. According to the write protocol, the bus master then
sends the address bytes that are loaded into the internal address
latch. After the FM31276/FM31278 acknowledges the address,
the bus master issues a START condition. This simultaneously
aborts the write operation and allows the read command to be
issued with the slave address LSB set to a ‘1’. The operation is
now a current address read.
RTC/Companion Write Operation
All RTC and Companion writes operate in a similar manner to
memory writes. The distinction is that a different device ID is
used and only one byte address is needed instead of two byte
address. Figure 22 illustrates a single byte write to this device.
Note Although not required, it is recommended that A5-A7 in the
register address byte are zeros in order to preserve compatibility
with future devices.
RTC/Companion Read Operation
As with writes, a read operation begins with the Slave Address.
To perform a register read, the bus master supplies a Slave
Address with the LSB set to ‘1’. This indicates that a read
operation is requested. After receiving the complete Slave
Address, the FM31276/FM31278 will begin shifting data out from
the current register address on the next clock. Auto-increment
operates for the special function registers as with the memory
address. A current address read for the registers look exactly like
the memory except that the device ID is different.
The FM31276/FM31278 contains two separate address
registers, one for the memory address and the other for the
register address. This allows the contents of one address
register to be modified without affecting the current address of
the other register. For example, this would allow an interrupted
read to the memory while still providing fast access to an RTC
register. A subsequent memory read will then continue from the
memory address where it previously left off, without requiring the
load of a new memory address. However, a write sequence
always requires an address to be supplied.
Addressing FRAM Array in the FM31276/FM31278
Family
The FM31276/FM31278 family includes 64-Kbit and 256-Kbit
memory densities. The following 2-byte address field is shown
for each density.
Figure 21. Selective (Random) Read
S ASlave Address 1Data Byte 1 P
By Master
By F-RAM
Start Address
Stop
No
Acknowledge
Data
S ASlave Address 0Address MSB A
Start
Address
Acknowledge
Address LSB A
Figure 22. Single Byte Write
S
A
Slave Address
0
A
ddress
A
Data Byte
A
P
By Maste
r
Star
t
A
ddress & Data Stop
A
cknowledge
000
By F-RAM
Part Number 1st Address Byte 2nd Address Byte
FM31276 X X X A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0
FM31278 X A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 26 of 36
Maximum Ratings
Exceeding maximum ratings may shorten the useful life of the
device. These user guidelines are not tested.
Storage temperature ................................ –65 °C to +125 °C
Ambient Temperature
with power applied ................................... –55 °C to +125 °C
Supply voltage on VDD relative to VSS .........–1.0 V to +7.0 V
Input voltage ........... –1.0 V to +7.0 V and VIN < VDD + 1.0 V
Backup supply voltage .................................–1.0 V to +4.5 V
DC voltage applied to outputs
in High-Z state .................................... –0.5 V to VDD + 0.5 V
Transient voltage (< 20 ns)
on any pin to ground potential ............ –2.0 V to VDD + 2.0 V
Package power dissipation capability
(TA = 25 °C) ................................................................. 1.0 W
Surface mount lead soldering temperature
(3 seconds) .............................................................. +260 °C
DC output current
(1 output at a time, 1s duration) .................................. 15 mA
Electrostatic Discharge Voltage
Human Body Model (AEC-Q100-002 Rev. D) ..................... 2 kV
Charged Device Model (AEC-Q100-011 Rev. B) ............. 1.25 kV
Machine Model (AEC-Q100-003 Rev. E) ............................ 100 V
Latch-up current .................................................. > ±100 mA
Note PFI input voltage must not exceed 4.5 V. The
“VIN < VDD + 1.0 V” restriction does not apply to the SCL and
SDA inputs which do not employ a diode to VDD.
Operating Range
Range Ambient Temperature (TA) VDD
Industrial –40 C to +85 C 4.0 V to 5.5 V
DC Electrical Characteristics
Over the Operating Range
Parameter Description Test Conditions Min Typ [1] Max Unit
VDD[2] Power supply 4.0 – 5.5 V
IDD Average VDD current SCL toggling
between
VDD
– 0.3 V and VSS,
other inputs
VSS or VDD – 0.3 V.
fSCL = 100 kHz – – 500 A
fSCL = 400 kHz – – 900 A
fSCL = 1 MHz – – 1500 A
ISB VDD standby current SCL = SDA = VDD.
All other inputs
VSS or V
DD. Stop
command issued.
––150
A
VBAK[3] RTC backup voltage TA = +25 C to +85 C 1.55 – 3.75 V
TA = –40 C to +25 C 1.90 – 3.75 V
IBAK RTC backup current VBAK = 3.0 V,
VDD < 2.4 V,
oscillator running,
CNT1, CNT2 at
VBAK.
TA = +25 C,
VBAK = 3.0 V
––1.4
A
TA = +85 C,
VBAK = 3.0 V
––2.1
A
TA = +25 C,
VBAK = 2.0 V
– – 1.15 A
TA = +85 C,
VBAK = 2.0 V
– – 1.75 A
IBAKTC[4] Trickle charge current
with VBAK = 0 V
Fast Charge Off
(FC = ‘0’)
50 – 120 A
Fast Charge On
(FC = ‘1’)
200 – 2500 A
Notes
1. Typical values are at 25 °C, VDD = VDD(typ). Not 100% tested.
2. Full complete operation. Supervisory circuits, RTC, etc operate to lower voltages as specified.
3. The VBAK trickle charger automatically regulates the maximum voltage on this pin for capacitor backup applications.
4. VBAK will source current when trickle charge is enabled (VBC bit = ‘1’), VDD > VBAK, and VBAK < VBAK max.
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 27 of 36
VTP1 VDD trip point voltage, VTP = 0 RST is asserted active when VDD < VTP
. 3.75 3.90 4.00 V
VTP2 VDD trip point voltage, VTP = 1 RST is asserted active when VDD < VTP
. 4.20 4.40 4.50 V
VRST[5] VDD for valid RST I
OL = 80 A at VOL VBAK > VBAK min 0 – – V
VBAK < VBAK min 1.6 – – V
ILI Input leakage current VSS < VIN < VDD. Does not apply to A0, A1,
X1, PFI, RST, or X2
––±1
A
ILO Output leakage current VSS < VOUT < VDD. Does not apply to RST,
X1, or X2
––±1A
VIL[6] Input LOW voltage All inputs except as
listed below
– 0.3 – 0.3 × VDD V
CNT1, CNT2
battery-backed
(VDD < 2.5 V)
– 0.3 – 0.5 V
CNT1, CNT2
(VDD > 2.5 V)
– 0.3 – 0.8 V
VIH Input HIGH voltage All inputs except as
listed below
0.7 × VDD –V
DD + 0.3 V
CNT1, CNT2
battery-backed
(VDD < 2.5 V)
VBAK – 0.5 – VBAK + 0.3 V
CNT1, CNT2
(VDD > 2.5 V)
0.7 × VDD –V
DD + 0.3 V
PFI (comparator
input)
– – 3.75 V
VOH Output HIGH voltage IOH = –2 mA 2.4 – – V
VOL Output LOW voltage IOL = 3 mA – – 0.4 V
RRST Pull-up resistance for RST
inactive
50 – 400 k
Rin Input resistance (A1–A0) For VIN = VIL(Max) 20 – – k
For VIN = VIH(Min) 1 – – M
VPFI Power fail input reference voltage 1.140 1.20 1.225 V
VHYS Power fail input (PFI) hysteresis
(rising)
––100mV
DC Electrical Characteristics (continued)
Over the Operating Range
Parameter Description Test Conditions Min Typ [1] Max Unit
Notes
5. The minimum VDD to guarantee the level of RST remains a valid VOL level.
6. Includes RST input detection of external reset condition to trigger driving of RST signal by FM31276/FM31278.
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 28 of 36
AC Test Conditions
Input pulse levels .................................10% and 90% of VDD
Input rise and fall times .................................................10 ns
Input and output timing reference levels ................0.5 × VDD
Output load capacitance ............................................ 100 pF
Data Retention and Endurance
Parameter Description Test condition Min Max Unit
TDR Data retention TA = 85 C 10 – Years
TA = 75 C38–
TA = 65 C151–
NVCEndurance Over operating temperature 1014 – Cycles
Capacitance
Parameter [7] Description Test Conditions Typ Max Unit
CIO Input/Output pin capacitance TA = 25 C, f = 1 MHz, VDD = VDD(typ) – 8 pF
CXTL[8] X1, X2 crystal pin capacitance 12 – pF
Thermal Resistance
Parameter [7] Description Test Conditions 14-pin SOIC Unit
JA Thermal resistance
(junction to ambient)
Test conditions follow standard test methods and
procedures for measuring thermal impedance, per
EIA/JESD51.
80 C/W
JC Thermal resistance
(junction to case)
29 C/W
AC Test Loads and Waveforms
Figure 23. AC Test Loads and Waveforms
5.5V
OUTPUT
100 pF
1.7 k
Notes
7. This parameter is characterized and not 100% tested.
8. The crystal attached to the X1/X2 pins must be rated as 6 pF/12.5 pF.
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 29 of 36
Supervisor Timing
Over the Operating Range
Parameter Description Min Max Units
tRPU RST active (LOW) after VDD > VTP 100 200 ms
tRNR[9] RST response time to VDD < VTP (noise filter) 10 25 s
tVR[9, 10] VDD power-up ramp rate 50 –s/V
tVF[9, 10] VDD power-down ramp rate 100 –s/V
tWDP[11] Pulse width of RST for watchdog reset 100 200 ms
tWDOG[11] Timeout of watchdog tDOG 2 × tDOG ms
fCNT Frequency of event counters 010 MHz
tOSC RTC Oscillator time to start – 2 s
Figure 24. RST Timing
V
DD
V
TP
V
RST
RST
t
RPU
t
VF
t
VR
t
RNR
Notes
9. This parameter is characterized and not 100% tested.
10. Slope measured at any point on VDD waveform.
11. tDOG is the programmed time in register in register 0Ah, VDD > VTP
, and tRPU satisfied.
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 30 of 36
AC Switching Characteristics
Over the Operating Range
Parameter [12]
Description Min Max Min Max Min Max Unit
Cypress
Parameter
Alt.
Parameter
fSCL SCL clock frequency 0 100 0 400 0 1000 kHz
tSU; STA Start condition setup for repeated Start 4.7 – 0.6 – 0.25 – s
tHD;STA Start condition hold time 4.0 – 0.6 – 0.25 – s
tLOW Clock LOW period 4.7 – 1.3 – 0.6 – s
tHIGH Clock HIGH period 4.0 – 0.6 – 0.4 – s
tSU;DAT tSU;DATA Data in setup 250–100–100– ns
tHD;DAT tHD;DATA Data in hold 0 – 0 – 0 – ns
tDH Data output hold (from SCL @ VIL) 0–0–0–ns
tR[13] trInput rise time – 1000 – 300 – 300 ns
tF[13] tfInput fall time – 300 – 300 – 100 ns
tSU;STO STOP condition setup 4 – 0.6 0.25 – s
tAA tVD;DATA SCL LOW to SDA Data Out Valid – 3 0.9 – 0.55 s
tBUF Bus free before new transmission 4.7 – 1.3 – 0.5 – s
tSP Noise suppression time constant on SCL, SDA – 50 50 – 50 ns
Figure 25. Read Bus Timing Diagram
Figure 26. Write Bus Timing Diagram
tSU:SDA
Start
tR
`tF
Stop Start
tBUF
tHIGH
1/fSCL
tLOW tSP tSP
Acknowledge
tHD:DAT
tSU:DAT
tAA tDH
SCL
SDA
tSU:STO
Start Stop Start Acknowledge
tAA
tHD:DAT
tHD:STA tSU:DAT
SCL
SDA
Notes
12. Test conditions assume a signal transition time of 10 ns or less, timing reference levels of 0.5 × VDD, input pulse levels of 10% to 90% of VDD, and output loading of
the specified IOL/IOH and 100 pF load capacitance shown in Figure 23 on page 28.
13. This parameter is characterized and not 100% tested.
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 31 of 36
Ordering Code Definitions
Ordering Information
Ordering Code Package
Diagram Package Type Operating
Range
FM31276-G 51-85067 14-pin SOIC Industrial
FM31276-GTR 51-85067 14-pin SOIC
FM31278-G 51-85067 14-pin SOIC
FM31278-GTR 51-85067 14-pin SOIC
All these parts are Pb-free. Contact your local Cypress sales representative for availability of these parts.
Option: XX = blank or TR
blank = Standard; TR = Tape and Reel
Package Type:
G = 14-pin SOIC
Density: XXX = 276 or 278
276 = 64-Kbit; 278 = 256-Kbit
I2C Processor Companion
Cypress
31FM XXX G XX-
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 32 of 36
Package Diagram
Figure 27. 14-pin SOIC (150 Mils) Package Outline, 51-85067
51-85067 *E
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 33 of 36
Acronyms Document Conventions
Units of Measure
Acronym Description
EEPROM Electrically Erasable Programmable Read-Only
Memory
EIA Electronic Industries Alliance
F-RAM Ferroelectric Random Access Memory
I2C Inter-Integrated Circuit
I/O Input/Output
JEDEC Joint Electron Devices Engineering Council
JESD JEDEC Standards
LSB Least Significant Bit
MSB Most Significant Bit
NMI Non Maskable interrupt
RoHS Restriction of Hazardous Substances
SOIC Small Outline Integrated Circuit
Symbol Unit of Measure
°C degree Celsius
Hz hertz
kHz kilohertz
kkilohm
Mbit megabit
MHz megahertz
Amicroampere
Fmicrofarad
smicrosecond
mA milliampere
ms millisecond
ns nanosecond
ohm
%percent
pF picofarad
Vvolt
Wwatt
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 34 of 36
Document History Page
Document Title: FM31276/FM31278, 64-Kbit/256-Kbit Integrated Processor Companion with F-RAM
Document Number: 001-86393
Rev. ECN No. Orig. of
Change
Submission
Date Description of Change
** 3916896 GVCH 02/28/2013 New spec.
*A 3924836 GVCH 03/07/2013 Changed status to Production.
Removed FM31274, FM31272 parts related information in all instances across
the document.
Removed 4Kb and 8Kb memory size related information in all instances across
the document.
Updated formatting.
*B 3985209 GVCH 05/02/2013 Updated DC Electrical Characteristics:
Changed minimum value of VTP1 parameter from 3.80 V to 3.75 V.
Changed minimum value of VTP2 parameter from 4.25 V to 4.20 V.
Changed minimum value of VPFI parameter from 1.175 V to 1.140 V.
*C 4333096 GVCH 05/05/2014 Updated Real-time Clock Operation:
Updated Crystal Oscillator:
Updated description (Added use of 6 pF crystal).
Updated Maximum Ratings:
Added “Maximum junction temperature” and its corresponding details.
Added “DC voltage applied to outputs in High-Z state” and its corresponding
details.
Added “Transient voltage (< 20 ns) on any pin to ground potential” and its
corresponding details.
Added “Package power dissipation capability (TA = 25 °C)” and its
corresponding details.
Added “DC output current (1 output at a time, 1s duration)” and its
corresponding details.
Added “Latch-up current” and its corresponding details.
Removed “Package Moisture Sensitivity Level” and its corresponding details.
Updated Data Retention and Endurance:
Updated details corresponding to TDR parameter.
Added NVC parameter and its corresponding details.
Updated Capacitance:
Changed typical value of CXTL parameter from 25 pF to 12 pF.
Added Thermal Resistance.
Updated Package Diagram:
Removed SOIC Package Marking Scheme.
Updated to Cypress template.
*D 4562106 GVCH 11/05/2014 Updated Functional Description:
Added “For a complete list of related documentation, click here.” at the end.
FM31276/FM31278
Document Number: 001-86393 Rev. *F Page 35 of 36
*E 6072167 GVCH 02/16/2018 Updated Register Map:
Updated Ta b le 6 :
Removed “VTP1” bit from bit 1 corresponding to address “0Bh”.
Replaced “VTP0” with “VTP” in bit 0 corresponding to address “0Bh”.
Updated details in “Description” column corresponding to OSCEN (to add tOSC
time in the 01h register).
Updated DC Electrical Characteristics:
Changed typical value of VTP2 parameter from 4.00 V to 4.40 V.
Updated Supervisor Timing:
Added tOSC parameter and its corresponding details.
Updated Package Diagram:
spec 51-85067 – Changed revision from *D to *E.
Updated to new template.
*F 6388437 GVCH 11/19/2018 Updated Maximum Ratings:
Replaced “–55 °C to +125 °C” with “–65 °C to +125 °C” in ratings corresponding
to “Storage temperature”.
Updated to new template.
Document History Page (continued)
Document Title: FM31276/FM31278, 64-Kbit/256-Kbit Integrated Processor Companion with F-RAM
Document Number: 001-86393
Rev. ECN No. Orig. of
Change
Submission
Date Description of Change
Document Number: 001-86393 Rev. *F Revised November 19, 2018 Page 36 of 36
FM31276/FM31278
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