Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (510) 668-7000 • FAX (510) 668-7017 • www.exar.com
XR18W750
WIRELESS UART CONTROLLER
MARCH 2008 REV. 1.0.0
GENERAL DESCRIPTION
The XR18W750 is a Wireless UART Controller with a
two-wire I2C interface to the XR18W753 RF
transceiver to complete Exar’s Wireless UART
chipset solution. The XR18W750 supports both the
parallel and serial interfaces to any host system thus
providing flexibility for system designers to select
their interface option.
The XR18W750 includes an embedded 8051
microprocessor which provides the power to process
the protocol framing for data transmission and to
handle error processing. Internally, the XR18W750
has a 32KB system memory for loading the firmware
from an external EEPROM and for data processing.
The XR18W750 also includes a 128-bit AES engine
for data encoding and decoding.
The XR18W750 is available in a 48-pin QFN
package.
APPLICATIONS
•Industrial Automation
•Factory Automation
•Point of Sales Systems
•Industrial Servers
•Data Collection Terminals
FEATURES
•2.25 to 3.63 Volt Operation
•5 Volt Tolerant Inputs
•8051 Microcontroller
•32KB System Memory
•128-bit AES Engine
•I2C Bus Master Interface to RF Transceivers
•Optional UART interface to RF Transceiver
•Selectable Serial or Parallel Mode Interface
•Enhanced UART
■16550 Compatible Register Set
■Parallel mode data rate from 1200 bps to 230.4
Kbps
■Serial mode data rate from 1200 bps to
921.6Kbps
■Transmit and Receive FIFOs of 64 bytes
■Programmable TX and RX FIFO Trigger Levels
■Transmit and Receive FIFO Level Counters
■Automatic Hardware (RTS/CTS) Flow Control
■Selectable Auto RTS Flow Control Hysteresis
■Full modem interface
•Device Identification and Revision
•48-pin QFN package
FIGURE 1. XR18W750 BLOCK DIAGRAM
UART
A2:A0
D7:D0
16/68#, CS#, IOW#, IOR#
INT, TXRDY#, RXRDY#
TX, RX, RTS#, CTS#,
DTR#, DSR#, CD#, RI# 8051
Microprocessor
AES
Encoding/
Decoding
S/P#
RESET
SDA
SCL
MODEM_RESET
RF_IRQ#
RF_DI
RF_DO
EN_DIDO
Parallel
Mode
Serial
Mode
CLK+
CLK-
GPIO[3:0]
I2C Interface
32KB
System
Memory
FIGURE 2. PIN OUT ASSIGNMENT
MODEM_RESET
GND
CLK-
CLK+
VCC
TEST2
TEST1
RF_IRQ#
RF_DO
RF_DI
SDA
SCL
XR18W750
EN_DIDO
TXRDY#
D7
D6
D5
D4
D3
D2
D1
D0
IOR#
VCC
GPIO3
GPIO2
GPIO1
TEST0
16/68#
IOW#
CS#
RXRDY#
A0
A1
A2
GND
GPIO0
INT
S/P#
RESET
TX
RX
DSR#
RTS#
RI#
CTS#
DTR#
CD#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
36
35
34
33
32
31
30
29
28
27
26
25
48
47
46
45
44
43
42
41
40
39
38
37
ORDERING INFORMATION
PART NUMBER PACKAGE OPERATING TEMPERATURE RANGE DEVICE STATUS
XR18W750IL48 48-Lead QFN -40°C to +85°C Active
XR18W750
2
WIRELESS UART CONTROLLER REV. 1.0.0
XR18W750
3
REV. 1.0.0 WIRELESS UART CONTROLLER
PIN DESCRIPTIONS
Pin Description
NAME 48-QFN
PIN # TYPE DESCRIPTION
PARALLEL MODE INTERFACE SIGNALS
A2
A1
A0
23
22
21
IAddress data lines [2:0]. These 3 address lines select one of the internal regis-
ters in the UART during a data bus transaction. The internal UART registers are
not accessed by the 8051 microprocessor in the parallel mode.
D7
D6
D5
D4
D3
D2
D1
D0
34
33
32
31
30
29
28
27
I/O Data bus lines [7:0] (bidirectional).
IOR#
(VCC)
26 IWhen 16/68# pin is HIGH, the Intel bus interface is selected and this input
becomes read strobe (active low). The falling edge instigates an internal read
cycle and retrieves the data byte from an internal register pointed by the address
lines [A2:A0], puts the data byte on the data bus to allow the host processor to
read it on the rising edge.
When 16/68# pin is LOW, the Motorola bus interface is selected and this input is
not used and should be connected to VCC.
IOW#
(R/W#)
18 IWhen 16/68# pin is HIGH, it selects Intel bus interface and this input becomes
write strobe (active low). The falling edge instigates the internal write cycle and
the rising edge transfers the data byte on the data bus to an internal register
pointed by the address lines.
When 16/68# pin is LOW, the Motorola bus interface is selected and this input
becomes read (HIGH) and write (LOW) signal.
CS# 19 IChip select (active low) signal.
INT
(IRQ#)
47 OWhen 16/68# pin is HIGH for Intel bus interface, this output is an active high
interrupt output. Upon power-up, this output is in three-state mode. The output
state is controlled by the user through the software setting of MCR[3]. The INT
output is enabled when MCR[3] is set to a logic 1. See MCR[3].
When 16/68# pin is LOW for Motorola bus interface, this output becomes an
active low, open drain interrupt output. An external pull-up resistor is required for
proper operation.
TXRDY# 35 OUART Transmitter Ready (active low). The output provides the TX FIFO/THR sta-
tus for transmit. See Table 3. If it is not used, leave it unconnected.
RXRDY# 20 OUART Receiver Ready (active low). This output provides the RX FIFO/RHR sta-
tus for receive. See Table 3. If it is not used, leave it unconnected.
SERIAL MODE INTERFACE SIGNALS
TX 44 OUART Transmit Data. Standard transmit and receive interface is enabled when
MCR[6] = 0. In this mode, the TX signal will be HIGH during reset or idle (no
data). If this pin is not used, leave it unconnected.
RX 43 IUART Receive Data. Normal receive data input must idle HIGH. If this pin is not
used, tie it to VCC or pull it high via a 100k ohm resistor.
XR18W750
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WIRELESS UART CONTROLLER REV. 1.0.0
RTS# 41 OUART Request-to-Send (active low) or general purpose output. This output must
be asserted prior to using auto RTS flow control, see EFR[6], MCR[1],
FCTR[1:0], EMSR[5:4] and IER[6].
CTS# 39 IUART Clear-to-Send (active low) or general purpose input. It can be used for
auto CTS flow control, see EFR[7], and IER[7]. This input should be connected to
VCC when not used.
DTR# 38 OUART Data-Terminal-Ready (active low) or general purpose output. If it is not
used, leave it unconnected.
DSR# 42 IUART Data-Set-Ready (active low) or general purpose input. This input should
be connected to VCC when not used. This input has no effect on the UART.
CD# 37 IUART Carrier-Detect (active low) or general purpose input. This input should be
connected to VCC when not used. This input has no effect on the UART.
RI# 40 IUART Ring-Indicator (active low) or general purpose input. This input should be
connected to VCC when not used. This input has no effect on the UART.
RF TRANSCEIVER INTERFACE SIGNALS
MODEM_RESET 1 O Reset output to the RF transceiver.
RF_IRQ# 8 I Interrupt input from RF transceiver.
SDA 11 I/O I2C Serial Data Line.
SCL 12 I/O I2C Serial Clock Line. The I2C clock frequency can be up to 400 KHz.
RF_DO 9 O Data out to RF transceiver.
RF_DI 10 IData in from RF transceiver.
EN_DIDO 36 IEnable RF_DI and RF_DO (active high) for sending data to and from RF trans-
ceiver. If I2C bus is used for this purpose, this input should be connected to
GND.
ANCILLARY SIGNALS
S/P# 46 ISerial or Parallel Mode select. If this pin is HIGH, then the serial interface will be
enabled. If this pin is LOW, then the parallel mode will be enabled.
16/68# 17 IIntel or Motorola Bus Select.
When 16/68# pin is HIGH, 16 or Intel Mode, the device will operate in the Intel
bus type of interface.
When 16/68# pin is LOW, 68 or Motorola mode, the device will operate in the
Motorola bus type of interface.
RESET
(RESET#)
45 IWhen 16/68# pin is HIGH for Intel bus interface, this input becomes RESET
(active high). When 16/68# pin is LOW for Motorola bus interface, this input
becomes RESET# (active low).
A 40 ns minimum active pulse on this pin will reset the internal registers and all
outputs. The UART transmitter output will be held HIGH, the receiver input will be
ignored and outputs are reset during reset period (see Table 15).
Pin Description
NAME 48-QFN
PIN # TYPE DESCRIPTION
XR18W750
5
REV. 1.0.0 WIRELESS UART CONTROLLER
Pin type: I=Input, O=Output, I/O= Input/output, OD=Output Open Drain.
CLK-
CLK+
3
4
I
I
16 MHz differential clock input or CMOS clock input. Use both signals for differ-
ential clock.
Connect CLK- to VCC to enable the CMOS/TTL clock mode. The external
CMOS/TTL clock should be connected to CLK+.
GPIO[3:0] 13, 14, 15,
48
I/O General Purpose I/O.
TEST2
TEST1
TEST0
6
7
16
I
I
I
Factor Test Modes (active high). For normal operation, connect these inputs to
GND.
VCC 5, 25 Pwr 2.97V to 3.63V power supply.
GND 2, 24 Pwr Power supply common, ground.
Pin Description
NAME 48-QFN
PIN # TYPE DESCRIPTION
XR18W750
6
WIRELESS UART CONTROLLER REV. 1.0.0
1.0 PRODUCT DESCRIPTION
The XR18W750 is a Digital Baseband with a two-wire I2C interface to the XR18W753 RF transceiver to
complete Exar’s Wireless UART chipset solution. An external I2C EEPROM is required to store Exar’s
proprietary firmware and Wireless UART chipset parameters.
The XR18W750 is functionally, as well as architecturally, divided into the following blocks and modules:
•8051 Microprocessor
•Enhanced UART
•AES Engine
•I2C Interface
1.1 8051 Microprocessor
The embedded 8051 microprocessor is compatible with the industry standard 803x/805x microprocessors
using a standard 8051 instruction set. The embedded 8051 microprocessor has a high-speed architecture that
takes four clocks per instruction cycle, eliminates wasted bus cycles and improves instruction execution time
on average by 2.5X over the standard 8051. The embedded 8051 microprocessor has a 32KB system
memory for loading the firmware from an external I2C EEPROM and for data processing. The firmware is
loaded from the external I2C EEPROM upon power on or reset. A 16MHz clock is required for correct
operation of the 8051 microprocessor. (This same 16MHz clock is also used by the enhanced UART in the
XR18W750.) For the firmware for communicating with the XR18W753 RF Transceiver, send an e-mail to
uarttechsupport@exar.com.
1.2 Enhanced UART
A CPU or serial port can communicate with the XR18W750 via the enhanced 64 byte FIFO UART. The
XR18W750 can communicate with an external CPU when the parallel mode is enabled (S/P# connected to
GND) or it can communicate directly with another serial port when the serial mode is enabled (S/P# connected
to VCC). The enhanced UART has a register set that is compatible to the industry standard 16550, but with
additional features such as Auto RTS/CTS Hardware Flow Control, Programmable TX and RX FIFO Trigger
Levels, and a Programmable Fractional Baud Rate Generator.
1.2.1 Parallel Mode
When the parallel mode is enabled, an external CPU can communicate with the enhanced UART via either the
Intel bus (CS#, IOR#, IOW#, INT) or Motorola bus (CS#, R/W#, IRQ#) interface. Any data that is written to the
TX FIFO of the enhance UART will be transmitted serially to UART of the 8051 microprocessor, where it is
processed and sent via the I2C interface to the RF Transceiver.
1.2.2 Serial Mode
When the serial mode is enabled, an external serial port can communicate with the enhanced UART via RS-
232, RS-422, or RS-485. The data that is received in the RX FIFO of the enhanced UART will be read out via
the parallel bus by the 8051 microprocessor, where it is processed and appropriate actions are taken. There
are two modes of operation in the serial mode: Command Mode and Data Mode. In the command mode, the
enhanced UART can be configured via AT commands.
1.3 AES Engine
The internal 128-bit AES engine guarantees that the data is transmitted securely from one Wireless UART
chipset to another Wireless UART chipset with the same AES security key. This prevents other wireless
devices on the same frequency to listen in on the Wireless UART chipset unless it knows the 128-bit AES
security key.
1.4 I2C Interface
The I2C interface on the XR18W750 operates in the I2C master mode. The I2C interface is a two-wire serial
interface consisting of a serial data line (SDA) and serial clock line (SCL). The maximum I2C clock frequency
is 400 kHz. The XR18W750 loads the firmware from the EEPROM and can communicate with an RF
Transceiver like the XR18W753 via the I2C interface.
XR18W750
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REV. 1.0.0 WIRELESS UART CONTROLLER
1.4.1 XR18W753 RF Transceiver
The XR18W753 is an RF Transceiver with frequency ranges of 868MHz - 954MHz and a data rate of 250kbps.
All of the Physical Layer Management Entity (PLME) registers to configure and control the XR18W753 can be
accessed via the I2C interface. See the XR18W753 datasheet for complete details.
1.4.2 External EEPROM
An external I2C EEPROM is required to store the firmware for the 8051 microprocessor and the parameters of
the Wireless UART chipset. The I2C EEPROM must have at least 32KB of memory.
1.4.2.1 EEPROM Parameters
The table below describes all of the parameters that are stored in the external I2C EEPROM.
TABLE 1: EEPROM PARAMATERS
PARAMETER BYTES DESCRIPTION
Source ID 4These bytes are sent in the packet preamble to identify who is sending the
packet in P2P mode.
Destination ID 4These bytes are sent in the packet preamble to identify who is to receive
the packet in the P2P mode.
Baud Rate 4These 4 bytes store the default baud rate that the UART will be initialized
to during the next power-up.
Communication Mode 1This parameter selects the communication mode: P2P, P2M, Broadcast.
Channel Number (Frequency) 1This byte stores the default or last used channel frequency of the
XR18W753 RF Transceiver.
Number of Retries 1This byte stores the number of times to re-transmit a packet when an ACK
is not received in P2P mode before giving up.
Group ID 1These bytes are compared by the recipient when a broadcast packet has
been received.
Power Level 1This byte stores the default power level for the XR18W753.
XR18W753 address 1This byte stores the I2C address of the XR18W753.
Autobaud Detect 1This byte selects whether the device has the Autobaud Detect feature
enabled upon power-up.
Power-up Mode 1This byte selects whether the device powers up in the command or the
data mode.
AES Security Key 16 This parameter is used for as the encoding/decoding key in the AES
Engine.
2.0 COMMUNICATION MODES
2.1 Point-to-Point
Point-to-point communication is similar to two UARTs communicating via RS-232 or RS-422. The differences
being that the communication is now wireless and half-duplex. Each time a wireless data packet is
transmitted, the Wireless UART chipset waits until an ACK is received. If an ACK has not been received, the
Wireless UART chipset will re-transmit the packet. The Wireless UART chipset will attempt to re-transmit the
packet until the specified number of retries has been reached.
In this communication mode, the packet will only be received and an ACK will be sent if the two Wireless UART
chipsets are configured for the same frequency, with matching AES security keys and the Destination ID of the
packet matches the Source ID of the Wireless UART chipset.
XR18W750
8
WIRELESS UART CONTROLLER REV. 1.0.0
2.2 Point-to-Multipoint (Group Mode)
Point-to-multipoint communication, also known as Group mode, is when one master station transmits a packet
to all Wireless UART chipsets with the same Group ID. All Wireless UART chipsets with the same Group ID
will receive the message. No ACK will be sent by the receiving stations and no ACK is expected by the master
station. The Source and Destination ID is not checked in this communication mode.
2.3 Broadcast
The broadcast mode is when one master station transmits a packet and is received by all Wireless UART
chipsets that are on the same channel frequency and that have the same AES security key. In this case, the
Source ID, Destination ID and Group ID are not checked. No ACK will be sent by the receiving stations and no
ACK is expected by the master station.
3.0 ENHANCED UART DESCRIPTION
3.1 Serial Mode Interface
In the serial mode, the enhanced UART is controlled by the 8051 processor. The enhanced UART can
communicate with another serial port via RS-232, RS-485, or RS-422. A typical connection for the serial mode
of operation is shown below.
FIGURE 3. XR18W750 TYPICAL CONNECTIONS (SERIAL MODE)
8051
Microprocessor
S/P#
TX
RX
RTS#
CTS#
DTR#
DSR#
CD#
RI#
A2:A0
D7:D0
CS#
IOW#
IOR#
A2:A0
D7:D0
CS#
IOW#
IOR#
TXRDY#
RXRDY#
TXRDY#
RXRDY#
16/68#
VCC
UART
VCC
INT INT
UART
TX
RX
RTS#
CTS#
DTR#
DSR#
CD#
RI#
In the serial mode, the external serial port will need to communicate with the UART via AT commands.
3.1.1 Auto Baud Rate Detect
Upon power-up, the XR18W750 can automatically detect any baud rate from 1200 bps to 230.4Kbps in the
parallel mode or from 1200 bps to 921.6Kbps in the serial mode. The only requirement is that the carriage
return character (0x0D) is sent twice to the enhanced UART. After that the enhanced UART will be configured
for the correct baud rate.
XR18W750
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REV. 1.0.0 WIRELESS UART CONTROLLER
3.1.2 AT Commands
The AT Commands supported are given in the table below.
TABLE 2: AT COMMANDS
SYNTAX DESCRIPTION EXAMPLE
ATI3 Displays the firmware version. ATI3<Enter>
AT+PPM=[x] 0 = Enable Point-to-Point Mode (P2P)
1 = Enable Point-To-Multipoint Mode (P2M)
2 = Enable Broadcast Mode
AT+PPM=0<Enter>
AT+SID=[xxxxxxxx] Source address. The range is 0x1 to 0xFFFFFFFD.
0xFFFFFFFE and 0xFFFFFFFF are reserved.
AT+SID = 38437452<Enter>
// Source Address = 0x38437452
AT+DID Destination address. The range is 0x1 to 0xFFFFFFFD.
0xFFFFFFFE and 0xFFFFFFFF are reserved.
AT+DID=23437<Enter>
// Destination address = 0x23437
AT+BDR=[xxxxxx] Change baud rate to 1200, 2400, 4800, 9600, 19200,
38400, 57600, 115200, 230400 bps.
AT+BDR=19200<Enter>
AT+GID=[xxx] Group ID. The valid range is 0x1 to 0xFE. AT+GID=10<Enter>
//Set group ID = 10
AT+CHN=[xx] Sets the RF channel number for the device. See the
XR18W753 for the valid channel range.
AT+CHN=2<Enter>
//Set channel number = 2
AT+NRE=[x] Number of Retries. The range is 0x1 to 0xA. AT+NRE=3<Enter>
//Set the number of retries to 3
AT+PWR=[x] Power level of RF transmitter. The range is 0x1 to 0x8 AT+PWR=1
//Set the power level = -3dbm
AT&V Display the current values of the source address, desti-
nation address, baud rate, channel number, etc.
AT&V<Enter>
ATO Switch from command mode to data mode. ATO<Enter>
+++ Switch from data mode to command mode. The time
between each "+" should be between 250ms and 1 sec.
+++
AT+KEY=
[xxxxxxxx
xxxxxxxx
xxxxxxxx
xxxxxxxx]
Sets a key for the AES engine AT+KEY=0001020304050607
08090A0B0C0D0E0F<Enter>
//Set the AES key to the specified
//value
AT+I2C=[xx] Change the I2C address of the RF Transceiver. AT+I2C=60<Enter>
// Change I2C address to 0x60
AT+MOD=[x] 0 = Power-up in command mode
1 = Power-up in data mode
AT+MOD=1<Enter>
AT+ABD=[x] 0 = Autobaud detect disabled at next power-up
1 = Autobaud detect enabled at next power-up
AT+ABD=1<Enter>
XR18W750
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WIRELESS UART CONTROLLER REV. 1.0.0
3.2 Parallel Mode (CPU) Interface
In the parallel mode, the CPU interface is 8 data bits wide with 3 address lines and control signals to execute
data bus read and write transactions. The XR18W750 data interface supports both the Intel and Motorola
compatible types of CPUs and is compatible to the industry standard 16C550 UART. Each bus cycle is
asynchronous using CS#, IOR# and IOW#, or CS# and R/W# inputs. A typical data bus interconnection for
Intel and Motorola mode is shown in Figure 4.
FIGURE 4. XR18W750 TYPICAL INTEL/MOTOROLA DATA BUS INTERCONNECTIONS (PARALLEL MODE)
8051
Microprocessor
S/P#
A2:A0
D7:D0
CS#
IOW#
IOR#
INT
A2:A0
D7:D0
CS#
IOW#
IOR#
RESET
A2:A0
D7:D0
UART_CS#
IOW#
IOR#
RESET
TXRDY#
RXRDY#
TXRDY#
RXRDY#
16/68#VCC
UART
GND
INTUART_INT
Intel Data Bus Interconnections
UART
RX
TX
CTS#
RTS#
TX
RX
RTS#
CTS#
8051
Microprocessor
S/P#
A2:A0
D7:D0
CS#
IOW#
IOR#
INT
A2:A0
D7:D0
CS#
IOW#
IOR#
RESET
A2:A0
D7:D0
UART_CS#
R/W#
VCC
RESET#
TXRDY#
RXRDY#
TXRDY#
RXRDY#
16/68#GND
UART
GND
INTUART_IRQ#
VCC
Motorola Data Bus Interconnections
UART
RX
TX
CTS#
RTS#
TX
RX
RTS#
CTS#
XR18W750
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REV. 1.0.0 WIRELESS UART CONTROLLER
3.3 Device Reset
The RESET input resets the internal registers and the serial interface outputs to their default state (see
Table 15). An active high pulse of longer than 40 ns duration will be required to activate the reset function in
the device.
3.4 Device Identification and Revision
The XR18W750 has the same Device ID as the XR16L275x and XR16V275x. To read the identification code
from the part, it is required to set the baud rate generator registers DLL and DLM both to 0x00. Now reading
the content of the DLM will provide 0x0A and reading the content of DLL will provide the revision of the part; for
example, a reading of 0x01 means revision A.
3.5 Internal Registers
The enhanced UART has a set of registers for control, monitoring and data loading and unloading. The
configuration register set is compatible to those already available in the standard single 16C550. These
registers function as data holding registers (THR/RHR), interrupt status and control registers (ISR/IER), a FIFO
control register (FCR), receive line status and control registers (LSR/LCR), modem status and control registers
(MSR/MCR), programmable data rate (clock) divisor registers (DLL/DLM), and a user accessible Scratchpad
Register (SPR).
Beyond the general 16C550 features and capabilities, the XR18W750 offers enhanced feature registers
(EMSR, FLVL, EFR, FCTR, TRG, FC) that provide automatic RTS and CTS hardware flow control, FIFO trigger
level control, and FIFO level counters. All the register functions are discussed in full detail later in “Section 4.0,
UART INTERNAL REGISTERS” on page 18.
3.6 DMA Mode
The device does not support direct memory access. The DMA Mode (a legacy term) in this document doesn’t
mean “direct memory access” but refers to data block transfer operation. The DMA mode affects the state of
the RXRDY# and TXRDY# output pins. The transmit and receive FIFO trigger levels provide additional
flexibility to the user for block mode operation. The LSR bits 5-6 provide an indication when the transmitter is
empty or has an empty location(s) for more data. The user can optionally operate the transmit and receive
FIFO in the DMA mode (FCR bit-3=1). When the transmit and receive FIFO are enabled and the DMA mode is
disabled (FCR bit-3 = 0), the enhanced UART is placed in single-character mode for data transmit or receive
operation. When DMA mode is enabled (FCR bit-3 = 1), the user takes advantage of block mode operation by
loading or unloading the FIFO in a block sequence determined by the programmed trigger level. In this mode,
the enhanced UART sets the TXRDY# pin when the transmit FIFO becomes full, and sets the RXRDY# pin
when the receive FIFO becomes empty. The following table shows their behavior. Also see Figures 16
through 21.
TABLE 3: TXRDY# AND RXRDY# OUTPUTS IN FIFO AND DMA MODE
PINS FCR BIT-0=0
(FIFO DISABLED)FCR BIT-0=1 (FIFO ENABLED)
FCR Bit-3 = 0
(DMA Mode Disabled)
FCR Bit-3 = 1
(DMA Mode Enabled)
RXRDY# LOW = 1 byte.
HIGH = no data.
LOW = at least 1 byte in FIFO.
HIGH = FIFO empty.
HIGH to LOW transition when FIFO reaches the
trigger level, or time-out occurs.
LOW to HIGH transition when FIFO empties.
TXRDY# LOW = THR empty.
HIGH = byte in THR.
LOW = FIFO empty.
HIGH = at least 1 byte in FIFO.
LOW = FIFO has at least 1 empty location.
HIGH = FIFO is full.
XR18W750
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WIRELESS UART CONTROLLER REV. 1.0.0
3.7 INT (IRQ#) Output
The INT interrupt output changes according to the operating mode and enhanced features setup. Table 4
and 5 summarize the operating behavior for the transmitter and receiver. When operating in the Motorola bus
mode, the IRQ# output is the opposite polarity of the INT output. Also see Figures 16 through 21.
TABLE 4: INT PIN OPERATION FOR TRANSMITTER
FCR BIT-0 = 0
(FIFO DISABLED)FCR BIT-0 = 1 (FIFO ENABLED)
INT Pin LOW = a byte in THR
HIGH = THR empty
LOW = FIFO above trigger level
HIGH = FIFO below trigger level or FIFO empty
TABLE 5: INT PIN OPERATION FOR RECEIVER
FCR BIT-0 = 0
(FIFO DISABLED)
FCR BIT-0 = 1
(FIFO ENABLED)
INT Pin LOW = no data
HIGH = 1 byte
LOW = FIFO below trigger level
HIGH = FIFO above trigger level
3.8 Programmable Baud Rate Generator
The enhanced UART has a programmable Baud Rate Generator (BRG) for the transmitter and receiver. The
divisor values for the specific data rates are given in the table below.
TABLE 6: UART DATA RATES
Data Rate
DIVISOR FOR 16x
Clock
(Decimal)
DLM VALUE
(HEX)
DLL VALUE
(HEX)
300 3333.333 0D 05
600 1666.667 06 82
2400 416.667 01 A0
4800 208.333 00 D0
9600 104.167 00 68
19200 52.083 00 34
38400 26.042 00 1A
57600 17.361 00 11
115200 8.681 00 8
230400 400 4
3.9 Transmitter
The transmitter section comprises of an 8-bit Transmit Shift Register (TSR) and 64 bytes of FIFO which
includes a byte-wide Transmit Holding Register (THR). TSR shifts out every data bit with the 16X internal
clock. A bit time is 16 clock periods. The transmitter sends the start-bit followed by the number of data bits,
inserts the proper parity-bit if enabled, and adds the stop-bit(s). The status of the FIFO and TSR are reported in
the Line Status Register (LSR bit-5 and bit-6).
3.9.1 Transmit Holding Register (THR) - Write Only
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REV. 1.0.0 WIRELESS UART CONTROLLER
The transmit holding register is an 8-bit register providing a data interface to the host processor. The host
writes transmit data byte to the THR to be converted into a serial data stream including start-bit, data bits,
parity-bit and stop-bit(s). The least-significant-bit (Bit-0) becomes first data bit to go out. The THR is the input
register to the transmit FIFO of 64 bytes when FIFO operation is enabled by FCR bit-0. Every time a write
operation is made to the THR, the FIFO data pointer is automatically bumped to the next sequential data
location.
3.9.2 Transmitter Operation in non-FIFO Mode
The host loads transmit data to THR one character at a time. The THR empty flag (LSR bit-5) is set when the
data byte is transferred to TSR. THR flag can generate a transmit empty interrupt (ISR bit-1) when it is enabled
by IER bit-1. The TSR flag (LSR bit-6) is set when TSR becomes completely empty.
FIGURE 5. TRANSMITTER OPERATION IN NON-FIFO MODE
Transmit
Holding
Register
(THR)
Transmit Shift Register (TSR)
Data
Byte
L
S
B
M
S
B
THR Interrupt (ISR bit-1)
Enabled by IER bit-1
TXNOFIFO1
16X Clock
3.9.3 Transmitter Operation in FIFO Mode
The host may fill the transmit FIFO with up to 64 bytes of transmit data. The THR empty flag (LSR bit-5) is set
whenever the FIFO is empty. The THR empty flag can generate a transmit empty interrupt (ISR bit-1) when the
amount of data in the FIFO falls below its programmed trigger level. The transmit empty interrupt is enabled by
IER bit-1. The TSR flag (LSR bit-6) is set when TSR/FIFO becomes empty.
FIGURE 6. TRANSMITTER OPERATION IN FIFO AND FLOW CONTROL MODE
Transmit Data Shift Register
(TSR)
Transmit
Data Byte THR Interrupt (ISR bit-1) falls
below the programmed Trigger
Level and then when becomes
empty. FIFO is enabled by FCR
bit-0=1
Transmit
FIFO
16X Clock
Auto CTS Flow Control (CTS# pin)
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3.10 Receiver
The receiver section contains an 8-bit Receive Shift Register (RSR) and 64 bytes of FIFO which includes a
byte-wide Receive Holding Register (RHR). The RSR uses the 16X clock for timing. It verifies and validates
every bit on the incoming character in the middle of each data bit. On the falling edge of a start or false start bit,
an internal receiver counter starts counting at the 16X clock rate. After 8 clocks the start bit period should be at
the center of the start bit. At this time the start bit is sampled and if it is still a logic 0 it is validated. Evaluating
the start bit in this manner prevents the receiver from assembling a false character. The rest of the data bits
and stop bits are sampled and validated in this same manner to prevent false framing. If there were any
error(s), they are reported in the LSR register bits 2-4. Upon unloading the receive data byte from RHR, the
receive FIFO pointer is bumped and the error tags are immediately updated to reflect the status of the data
byte in RHR register. RHR can generate a receive data ready interrupt upon receiving a character or delay until
it reaches the FIFO trigger level. Furthermore, data delivery to the host is guaranteed by a receive data ready
time-out interrupt when data is not received for 4 word lengths as defined by LCR[1:0] plus 12 bits time. This is
equivalent to 3.7-4.6 character times. The RHR interrupt is enabled by IER bit-0.
3.10.1 Receive Holding Register (RHR) - Read-Only
The Receive Holding Register is an 8-bit register that holds a receive data byte from the Receive Shift
Register. It provides the receive data interface to the host processor. The RHR register is part of the receive
FIFO of 64 bytes by 11-bits wide, the 3 extra bits are for the 3 error tags to be reported in LSR register. When
the FIFO is enabled by FCR bit-0, the RHR contains the first data character received by the FIFO. After the
RHR is read, the next character byte is loaded into the RHR and the errors associated with the current data
byte are immediately updated in the LSR bits 2-4.
FIGURE 7. RECEIVER OPERATION IN NON-FIFO MODE
Receive Data Shift
Register (RSR)
Receive
Data Byte
and Errors
RHR Interrupt (ISR bit-2)
Receive Data
Holding Register
(RHR)
RXFIFO1
16X Clock
Receive Data Characters
Data Bit
Validation
Error
Tags in
LSR bits
4:2
FIGURE 8. RECEIVER OPERATION IN FIFO AND AUTO RTS FLOW CONTROL MODE
Receive Data Shift
Register (RSR)
RXFIFO1
16X Clock
Error Tags
(64-sets)
Error Tags in
LSR bits 4:2
64 bytes by 11-bit
wide
FIFO
Receive Data Characters
FIFO
Trigger=16
Example
:
- RX FIFO trigger level selected at 16 bytes
(See Note Below)
Data fills to 24
Data falls to 8
Data Bit
Validation
Receive
Data FIFO
Receive
Data
Receive Data
Byte and Errors
RHR Interrupt (ISR bit-2) programmed for
desired FIFO trigger level.
FIFO is Enabled by FCR bit-0=1
RTS# de-asserts when data fills above the flow
control trigger level to suspend remote transmitter.
Enable by EFR bit-6=1, MCR bit-1.
RTS# re-asserts when data falls below the flow
control trigger level to restart remote transmitter.
Enable by EFR bit-6=1, MCR bit-1.
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REV. 1.0.0 WIRELESS UART CONTROLLER
NOTE: Table-B selected as Trigger Table for Figure 8 (Table 10).
3.11 Auto RTS (Hardware) Flow Control
Automatic RTS hardware flow control is used to prevent data overrun to the local receiver FIFO. The RTS#
output is used to request remote unit to suspend/resume data transmission. The auto RTS flow control
features is enabled to fit specific application requirement (see Figure 9):
•Enable auto RTS flow control using EFR bit-6.
•The auto RTS function must be started by asserting RTS# output pin (MCR bit-1 to logic 1 after it is enabled).
If using the Auto RTS interrupt:
•Enable RTS interrupt through IER bit-6 (after setting EFR bit-4). The UART issues an interrupt when the
RTS# pin makes a transition from low to high: ISR bit-5 will be set to logic 1.
3.12 Auto RTS Hysteresis
With the Auto RTS function enabled, an interrupt is generated when the receive FIFO reaches the
programmed RX trigger level. The RTS# pin will not be forced HIGH (RTS off) until the receive FIFO reaches
the upper limit of the hysteresis level. The RTS# pin will return LOW after the RX FIFO is unloaded to the lower
limit of the hysteresis level. Under the above described conditions, the enhanced UART will continue to accept
data until the receive FIFO gets full. The Auto RTS function is initiated when the RTS# output pin is asserted
LOW (RTS On). Table 13 shows the complete details for the Auto RTS# Hysteresis levels. Please note that
this table is for programmable trigger levels only (Table D). The hysteresis values for Tables A-C are the next
higher and next lower trigger levels in the corresponding table.
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WIRELESS UART CONTROLLER REV. 1.0.0
3.13 Auto CTS Flow Control
Automatic CTS flow control is used to prevent data overrun to the remote receiver FIFO. The CTS# input is
monitored to suspend/restart the local transmitter. The auto CTS flow control feature is selected to fit specific
application requirement (see Figure 9):
•Enable auto CTS flow control using EFR bit-7.
If using the Auto CTS interrupt:
•Enable CTS interrupt through IER bit-7 (after setting EFR bit-4). The UART issues an interrupt when the
CTS# pin is de-asserted (HIGH): ISR bit-5 will be set to 1, and UART will suspend transmission as soon as
the stop bit of the character in process is shifted out. Transmission is resumed after the CTS# input is re-
asserted (LOW), indicating more data may be sent.
FIGURE 9. AUTO RTS AND CTS FLOW CONTROL OPERATION
RTSA# CTSB#
RXA TXB Transmitter
Receiver FIFO
Trigger Reached
Auto RTS
Trigger Level
Auto CTS
Monitor
RTSA#
TXB
RXA FIFO
CTSB#
Remote UART
UARTB
Local UART
UARTA
ON OFF ON
Suspend Restart
RTS High
Threshold
Data Starts
ON OFF ON
Assert RTS# to Begin
Transmission
1
2
3
4
5
6
7
Receive
Data RTS Low
Threshold
9
10
11
Receiver FIFO
Trigger Reached
Auto RTS
Trigger Level
Transmitter
Auto CTS
Monitor
RTSB#CTSA#
RXBTXA
INTA
(RXA FIFO
Interrupt)
RX FIFO
Trigger Level
RX FIFO
Trigger Level
8
12
RTSCTS1
The local UART (UARTA) starts data transfer by asserting RTSA# (1). RTSA# is normally connected to CTSB# (2) of
remote UART (UARTB). CTSB# allows its transmitter to send data (3). TXB data arrives and fills UARTA receive FIFO
(4). When RXA data fills up to its receive FIFO trigger level, UARTA activates its RXA data ready interrupt (5) and con-
tinues to receive and put data into its FIFO. If interrupt service latency is long and data is not being unloaded, UARTA
monitors its receive data fill level to match the upper threshold of RTS delay and de-assert RTSA# (6). CTSB# follows
(7) and request UARTB transmitter to suspend data transfer. UARTB stops or finishes sending the data bits in its trans-
mit shift register (8). When receive FIFO data in UARTA is unloaded to match the lower threshold of RTS delay (9),
UARTA re-asserts RTSA# (10), CTSB# recognizes the change (11) and restarts its transmitter and data flow again until
next receive FIFO trigger (12). This same event applies to the reverse direction when UARTA sends data to UARTB
with RTSB# and CTSA# controlling the data flow.
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REV. 1.0.0 WIRELESS UART CONTROLLER
3.14 Internal Loopback
The enhanced UART provides an internal loopback capability for system diagnostic purposes. The internal
loopback mode is enabled by setting MCR register bit-4 to logic 1. All regular UART functions operate normally.
Figure 10 shows how the modem port signals are re-configured. Transmit data from the transmit shift register
output is internally routed to the receive shift register input allowing the system to receive the same data that it
was sending. The TX, RTS# and DTR# pins are held while the CTS#, DSR# CD# and RI# inputs are ignored.
Caution: the RX input pin must be held HIGH during loopback test else upon exiting the loopback test the
UART may detect and report a false “break” signal. Also, Auto RTS/CTS flow control is not supported during
internal loopback.
FIGURE 10. INTERNAL LOOPBACK
TX
RX
Modem / General Purpose Control Logic
Internal Data Bus Lines and Control Signals
RTS#
MCR bit-4=1
VCC
VCC
Transmit Shift Register
(THR/FIFO)
Receive Shift Register
(RHR/FIFO)
CTS#
DTR#
DSR#
RI#
CD#
OP1#
RTS#
CTS#
DTR#
DSR#
RI#
CD#
VCC
OP2#
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WIRELESS UART CONTROLLER REV. 1.0.0
4.0 UART INTERNAL REGISTERS
The internal registers of the UART are selected by address lines A2-A0 in the parallel mode. In the serial
mode, the UART registers are not accessible via these address lines. The 8051 microprocessor does not
access the enhanced UART in the parallel mode. The complete register set is shown on Table 7 and Table 8.
TABLE 7: UART INTERNAL REGISTERS
ADDRESS REGISTER READ/WRITE COMMENTS
16C550 COMPATIBLE REGISTERS
0 0 0 RHR - Receive Holding Register
THR - Transmit Holding Register
Read-only
Write-only LCR[7] = 0
0 0 0 DLL - Divisor LSB Read/Write
LCR[7] = 1, LCR ≠ 0xBF
0 0 1 DLM - Divisor MSB Read/Write
0 0 0 DREV - Device Revision Code Read-only DLL, DLM = 0x00,
LCR[7] = 1, LCR ≠ 0xBF
0 0 1 DVID - Device Identification Code Read-only
0 0 1 IER - Interrupt Enable Register Read/Write LCR[7] = 0
0 1 0 ISR - Interrupt Status Register
FCR - FIFO Control Register
Read-only
Write-only LCR ≠ 0xBF
0 1 1 LCR - Line Control Register Read/Write
1 0 0 MCR - Modem Control Register Read/Write
LCR ≠ 0xBF1 0 1 LSR - Line Status Register Read-only
1 1 0 MSR - Modem Status Register Read-only
1 1 1 SPR - Scratch Pad Register Read/Write LCR ≠ 0xBF, FCTR[6] = 0
1 1 1 FLVL - RX/TX FIFO Level Counter Register Read-only
LCR ≠ 0xBF, FCTR[6] = 1
1 1 1 EMSR - Enhanced Mode Select Register Write-only
ENHANCED REGISTERS
0 0 0 TRG - RX/TX FIFO Trigger Level Register
FC - RX/TX FIFO Level Counter Register
Write-only
Read-only
LCR = 0xBF
0 0 1 FCTR - Feature Control Register Read/Write
0 1 0 EFR - Enhanced Function Register Read/Write
1 X X Rsrvd Read/Write
A2 A1 A0
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REV. 1.0.0 WIRELESS UART CONTROLLER
.
TABLE 8: INTERNAL REGISTERS DESCRIPTION. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1
ADDRESS
A2 A1 A0
REG
NAME
READ/
WRITE BIT-7 BIT-6 BIT-5 BIT-4 BIT-3 BIT-2 BIT-1 BIT-0 COMMENT
16C550 Compatible Registers
0 0 0 RHR RD Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
LCR[7]=0
0 0 0 THR WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
0 0 1 IER RD/WR 0/ 0/ 0/ 0Modem
Stat. Int.
Enable
RX Line
Stat.
Int.
Enable
TX
Empty
Int
Enable
RX
Data
Int.
Enable
CTS Int.
Enable
RTS Int.
Enable
0 1 0 ISR RD FIFOs
Enabled
FIFOs
Enabled
0/ 0/ INT
Source
Bit-3
INT
Source
Bit-2
INT
Source
Bit-1
INT
Source
Bit-0
LCR ≠ 0xBF
INT
Source
Bit-5
INT
Source
Bit-4
0 1 0 FCR WR RX FIFO
Trigger
RX FIFO
Trigger
0/ 0/ DMA
Mode
Enable
TX
FIFO
Reset
RX
FIFO
Reset
FIFOs
Enable
TX FIFO
Trigger
TX FIFO
Trigger
0 1 1 LCR RD/WR Divisor
Enable
Set TX
Break
Set Par-
ity
Even
Parity
Parity
Enable
Stop
Bits
Word
Length
Bit-1
Word
Length
Bit-0
1 0 0 MCR RD/WR 0/ 0/ 0/ Internal
Lopback
Enable
OP2#/INT
Output
Enable
Rsrvd
(OP1#)
RTS#
Output
Control
DTR#
Output
Control
LCR ≠ 0xBF
1 0 1 LSR RD RX FIFO
Global
Error
THR &
TSR
Empty
THR
Empty
RX
Break
RX Fram-
ing Error
RX
Parity
Error
RX
Over-
run
Error
RX
Data
Ready
1 1 0 MSR RD CD#
Input
RI#
Input
DSR#
Input
CTS#
Input
Delta
CD#
Delta
RI#
Delta
DSR#
Delta
CTS#
1 1 1 SPR RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 LCR ≠ 0xBF
FCTR[6]=0
1 1 1 EMSR WR Rsrvd
(1)
LSR
Error
Inter-
rupt.
Imd/Dly#
Auto
RTS
Hyst.
bit-3
Auto
RTS
Hyst.
bit-2
Rsrvd Rsrvd Rx/Tx
FIFO
Count
Rx/Tx
FIFO
Count
LCR ≠ 0xBF
FCTR[6]=1
1 1 1 FLVL RD Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
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WIRELESS UART CONTROLLER REV. 1.0.0
5.0 INTERNAL REGISTER DESCRIPTIONS
5.1 Receive Holding Register (RHR) - Read- Only
SEE”RECEIVER” ON PAGE 14.
5.2 Transmit Holding Register (THR) - Write-Only
SEE”TRANSMITTER” ON PAGE 12.
5.3 Interrupt Enable Register (IER) - Read/Write
The Interrupt Enable Register (IER) masks the interrupts from receive data ready, transmit empty, line status
and modem status registers. These interrupts are reported in the Interrupt Status Register (ISR).
Baud Rate Generator Divisor
0 0 0 DLL RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 LCR[7]=1
LCR ≠ 0xBF
0 0 1 DLM RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
0 0 0 DREV RD Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 LCR[7]=1
LCR ≠ 0xBF
DLL=0x00
DLM=0x00
0 0 1 DVID RD 0 0 0 0 1 0 1 0
Enhanced Registers
0 0 0 TRG WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
LCR=0XBF
0 0 0 FC RD Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
0 0 1 FCTR RD/WR RX/TX
Mode
SCPAD
Swap
Trig
Tab l e
Bit-1
Trig
Tab l e
Bit-0
Rsrvd Rsrvd Auto
RTS
Hyst
Bit-1
Auto
RTS
Hyst
Bit-0
0 1 0 EFR RD/WR Auto
CTS
Enable
Auto
RTS
Enable
Rsrvd Enable
IER [7:4],
ISR [5:4],
FCR[5:4],
MCR[7:5]
Rsrvd Rsrvd Rsrvd Rsrvd
1 X X Rsrvd RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
TABLE 8: INTERNAL REGISTERS DESCRIPTION. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1
ADDRESS
A2 A1 A0
REG
NAME
READ/
WRITE BIT-7 BIT-6 BIT-5 BIT-4 BIT-3 BIT-2 BIT-1 BIT-0 COMMENT
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REV. 1.0.0 WIRELESS UART CONTROLLER
5.3.1 IER versus Receive FIFO Interrupt Mode Operation
When the receive FIFO (FCR BIT-0 = 1) and receive interrupts (IER BIT-0 = 1) are enabled, the RHR interrupts
(see ISR bits 2 and 3) status will reflect the following:
A. The receive data available interrupts are issued to the host when the FIFO has reached the programmed
trigger level. It will be cleared when the FIFO drops below the programmed trigger level.
B. FIFO level will be reflected in the ISR register when the FIFO trigger level is reached. Both the ISR register
status bit and the interrupt will be cleared when the FIFO drops below the trigger level.
C. The receive data ready bit (LSR BIT-0) is set as soon as a character is transferred from the shift register to
the receive FIFO. It is reset when the FIFO is empty.
5.3.2 IER versus Receive/Transmit FIFO Polled Mode Operation
When FCR BIT-0 equals a logic 1 for FIFO enable; resetting IER bits 0-3 enables the FIFO polled mode of
operation. Since the receiver and transmitter have separate bits in the LSR either or both can be used in the
polled mode by selecting respective transmit or receive control bit(s).
A. LSR BIT-0 indicates there is data in RHR or RX FIFO.
B. LSR BIT-1 indicates an overrun error has occurred and that data in the FIFO may not be valid.
C. LSR BIT 2-4 provides the type of receive data errors encountered for the data byte in RHR, if any.
D. LSR BIT-5 indicates THR is empty.
E. LSR BIT-6 indicates when both the transmit FIFO and TSR are empty.
F. LSR BIT-7 indicates a data error in at least one character in the RX FIFO.
IER[0]: RHR Interrupt Enable
The receive data ready interrupt will be issued when RHR has a data character in the non-FIFO mode or when
the receive FIFO has reached the programmed trigger level in the FIFO mode.
•Logic 0 = Disable the receive data ready interrupt (default).
•Logic 1 = Enable the receiver data ready interrupt.
IER[1]: THR Interrupt Enable
This bit enables the Transmit Ready interrupt which is issued whenever the THR becomes empty in the non-
FIFO mode or when data in the FIFO falls below the programmed trigger level in the FIFO mode. If the THR is
empty when this bit is enabled, an interrupt will be generated.
•Logic 0 = Disable Transmit Ready interrupt (default).
•Logic 1 = Enable Transmit Ready interrupt.
IER[2]: Receive Line Status Interrupt Enable
If any of the LSR register bits 1, 2, 3 or 4 is a logic 1, it will generate an interrupt to inform the host controller
about the error status of the current data byte in FIFO. LSR bit-1 generates an interrupt immediately when the
character has been received. LSR bits 2-4 generate an interrupt when the character with errors is read out of
the FIFO (default). Instead, LSR bits 2-4 can be programmed to generate an interrupt immediately, by setting
EMSR bit-6 to a logic 1.
•Logic 0 = Disable the receiver line status interrupt (default).
•Logic 1 = Enable the receiver line status interrupt.
IER[3]: Modem Status Interrupt Enable
•Logic 0 = Disable the modem status register interrupt (default).
•Logic 1 = Enable the modem status register interrupt.
IER[4]: Reserved
This bit is reserved and should remain at a logic 0.
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WIRELESS UART CONTROLLER REV. 1.0.0
IER[5]: Reserved
For normal operation, this bit should be ’0’.
IER[6]: RTS# Output Interrupt Enable (requires EFR bit-4=1)
•Logic 0 = Disable the RTS# interrupt (default).
•Logic 1 = Enable the RTS# interrupt. The UART issues an interrupt when the RTS# pin makes a transition
from low to high.
IER[7]: CTS# Input Interrupt Enable (requires EFR bit-4=1)
•Logic 0 = Disable the CTS# interrupt (default).
•Logic 1 = Enable the CTS# interrupt. The UART issues an interrupt when CTS# pin makes a transition from
low to high.
5.4 Interrupt Status Register (ISR) - Read-Only
The UART provides multiple levels of prioritized interrupts to minimize external software interaction. The
Interrupt Status Register (ISR) provides the user with six interrupt status bits. Performing a read cycle on the
ISR will give the user the current highest pending interrupt level to be serviced, others are queued up to be
serviced next. No other interrupts are acknowledged until the pending interrupt is serviced. The Interrupt
Source Table, Table 9, shows the data values (bit 0-5) for the interrupt priority levels and the interrupt sources
associated with each of these interrupt levels.
5.4.1 Interrupt Generation:
•LSR is by any of the LSR bits 1, 2, 3 and 4.
•RXRDY is by RX trigger level.
•RXRDY Time-out is by a 4-char plus 12 bits delay timer.
•TXRDY is by TX trigger level or TX FIFO empty.
•MSR is by any of the MSR bits 0, 1, 2 and 3.
•CTS# is when its transmitter toggles the input pin (from LOW to HIGH) during auto CTS flow control.
•RTS# is when its receiver toggles the output pin (from LOW to HIGH) during auto RTS flow control.
5.4.2 Interrupt Clearing:
•LSR interrupt is cleared by a read to the LSR register.
•RXRDY interrupt is cleared by reading data until FIFO falls below the trigger level.
•RXRDY Time-out interrupt is cleared by reading RHR.
•TXRDY interrupt is cleared by a read to the ISR register or writing to THR.
•MSR interrupt is cleared by a read to the MSR register.
•RTS# and CTS# flow control interrupts are cleared by a read to the MSR register.
]
TABLE 9: INTERRUPT SOURCE AND PRIORITY LEVEL
PRIORITY ISR REGISTER STATUS BITS SOURCE OF INTERRUPT
LEVEL BIT-5 BIT-4 BIT-3 BIT-2 BIT-1 BIT-0
1 0 0 0 1 1 0 LSR (Receiver Line Status Register)
2 0 0 1 1 0 0 RXRDY (Receive Data Time-out)
3 0 0 0 1 0 0 RXRDY (Received Data Ready)
4 0 0 0 0 1 0 TXRDY (Transmit Ready)
5 0 0 0 0 0 0 MSR (Modem Status Register)
7 1 0 0 0 0 0 CTS#, RTS# change of state
- 0 0 0 0 0 1 None (default) or Wake-up Indicator
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REV. 1.0.0 WIRELESS UART CONTROLLER
ISR[0]: Interrupt Status
•Logic 0 = An interrupt is pending and the ISR contents may be used as a pointer to the appropriate interrupt
service routine.
•Logic 1 = No interrupt pending (default condition).
ISR[3:1]: Interrupt Status
These bits indicate the source for a pending interrupt at interrupt priority levels (See Interrupt Source Table 9).
ISR[4]: Reserved
ISR[5]: RTS#/CTS# Interrupt Status
This bit is enabled when EFR bit-4 is set to a logic 1. ISR bit-5 indicates that the CTS# or RTS# has been de-
asserted.
ISR[7:6]: FIFO Enable Status
These bits are set to a logic 0 when the FIFOs are disabled. They are set to a logic 1 when the FIFOs are
enabled.
5.5 FIFO Control Register (FCR) - Write-Only
This register is used to enable the FIFOs, clear the FIFOs, set the transmit/receive FIFO trigger levels, and
select the DMA mode. The DMA, and FIFO modes are defined as follows:
FCR[0]: TX and RX FIFO Enable
•Logic 0 = Disable the transmit and receive FIFO (default).
•Logic 1 = Enable the transmit and receive FIFOs. This bit must be set to logic 1 when other FCR bits are
written or they will not be programmed.
FCR[1]: RX FIFO Reset
This bit is only active when FCR bit-0 is a ‘1’.
•Logic 0 = No receive FIFO reset (default)
•Logic 1 = Reset the receive FIFO pointers and FIFO level counter logic (the receive shift register is not
cleared or altered). This bit will return to a logic 0 after resetting the FIFO.
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WIRELESS UART CONTROLLER REV. 1.0.0
FCR[2]: TX FIFO Reset
This bit is only active when FCR bit-0 is a ‘1’.
•Logic 0 = No transmit FIFO reset (default).
•Logic 1 = Reset the transmit FIFO pointers and FIFO level counter logic (the transmit shift register is not
cleared or altered). This bit will return to a logic 0 after resetting the FIFO.
FCR[3]: DMA Mode Select
Controls the behavior of the TXRDY# and RXRDY# pins. See DMA operation section for details.
•Logic 0 = Normal Operation (default).
•Logic 1 = DMA Mode.
FCR[5:4]: Transmit FIFO Trigger Select
(logic 0 = default, TX trigger level = 1)
These 2 bits set the trigger level for the transmit FIFO. The UART will issue a transmit interrupt when the
number of characters in the FIFO falls below the selected trigger level, or when it gets empty in case that the
FIFO did not get filled over the trigger level on last re-load. Table 10 below shows the selections. EFR bit-4
must be set to ‘1’ before these bits can be accessed. Note that the receiver and the transmitter cannot use
different trigger tables. Whichever selection is made last applies to both the RX and TX side.
FCR[7:6]: Receive FIFO Trigger Select
(logic 0 = default, RX trigger level =1)
The FCTR Bits 5-4 are associated with these 2 bits. These 2 bits are used to set the trigger level for the receive
FIFO. The UART will issue a receive interrupt when the number of the characters in the FIFO crosses the
trigger level. Table 10 shows the complete selections. Note that the receiver and the transmitter cannot use
different trigger tables. Whichever selection is made last applies to both the RX and TX side.
TABLE 10: TRANSMIT AND RECEIVE FIFO TRIGGER TABLE AND LEVEL SELECTION
TRIGGER
TABLE
FCTR
BIT-5
FCTR
BIT-4
FCR
BIT-7
FCR
BIT-6
FCR
BIT-5
FCR
BIT-4
RECEIVE
TRIGGER LEVEL
TRANSMIT
TRIGGER
LEVEL
COMPATIBILITY
Table-A 0 0
0
0
1
1
0
1
0
1
0 0
1 (default)
4
8
14
1 (default) 16C550, 16C2550,
16C2552, 16C554,
16C580
Table-B 0 1
0
0
1
1
0
1
0
1
0
0
1
1
0
1
0
1
8
16
24
28
16
8
24
30
16C650A
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REV. 1.0.0 WIRELESS UART CONTROLLER
5.6 Line Control Register (LCR) - Read/Write
The Line Control Register is used to specify the asynchronous data communication format. The word or
character length, the number of stop bits, and the parity are selected by writing the appropriate bits in this
register.
LCR[1:0]: TX and RX Word Length Select
These two bits specify the word length to be transmitted or received.
WORD LENGTH
0 0 5 (default)
0 1 6
1 0 7
1 1 8
LCR[2]: TX and RX Stop-bit Length Select
The length of stop bit is specified by this bit in conjunction with the programmed word length.
WORD
LENGTH
STOP BIT LENGTH
(BIT TIME(S))
05,6,7,8 1 (default)
1 5 1-1/2
16,7,8 2
Table-C 1 0
0
0
1
1
0
1
0
1
0
0
1
1
0
1
0
1
8
16
56
60
8
16
32
56
16C654
Table-D 1 1 X X X X Programmable
via TRG
register.
FCTR[7] = 0.
Programmable
via TRG
register.
FCTR[7] = 1.
16x275x, 16C285x,
16C850, 16C854,
16C864
BIT-1 BIT-0
BIT-2
TABLE 10: TRANSMIT AND RECEIVE FIFO TRIGGER TABLE AND LEVEL SELECTION
TRIGGER
TABLE
FCTR
BIT-5
FCTR
BIT-4
FCR
BIT-7
FCR
BIT-6
FCR
BIT-5
FCR
BIT-4
RECEIVE
TRIGGER LEVEL
TRANSMIT
TRIGGER
LEVEL
COMPATIBILITY
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WIRELESS UART CONTROLLER REV. 1.0.0
LCR[3]: TX and RX Parity Select
Parity or no parity can be selected via this bit. The parity bit is a simple way used in communications for data
integrity check. See Table 11 for parity selection summary below.
•Logic 0 = No parity.
•Logic 1 = A parity bit is generated during the transmission while the receiver checks for parity error of the
data character received.
LCR[4]: TX and RX Parity Select
If the parity bit is enabled with LCR bit-3 set to a logic 1, LCR bit-4 selects the even or odd parity format.
•Logic 0 = ODD Parity is generated by forcing an odd number of logic 1’s in the transmitted character. The
receiver must be programmed to check the same format (default).
•Logic 1 = EVEN Parity is generated by forcing an even number of logic 1’s in the transmitted character. The
receiver must be programmed to check the same format.
LCR[5]: TX and RX Parity Select
If the parity bit is enabled, LCR BIT-5 selects the forced parity format.
•LCR BIT-5 = logic 0, parity is not forced (default).
•LCR BIT-5 = logic 1 and LCR BIT-4 = logic 0, parity bit is forced to a logical 1 for the transmit and receive
data.
•LCR BIT-5 = logic 1 and LCR BIT-4 = logic 1, parity bit is forced to a logical 0 for the transmit and receive
data.
TABLE 11: PARITY SELECTION
LCR BIT-5 LCR BIT-4 LCR BIT-3 PARITY SELECTION
X X 0 No parity
0 0 1 Odd parity
0 1 1 Even parity
1 0 1 Force parity to mark, “1”
1 1 1 Forced parity to space, “0”
LCR[6]: Transmit Break Enable
When enabled, the Break control bit causes a break condition to be transmitted (the TX output is forced to a
“space", LOW state). This condition remains, until disabled by setting LCR bit-6 to a logic 0.
•Logic 0 = No TX break condition (default).
•Logic 1 = Forces the transmitter output (TX) to a “space”, LOW, for alerting the remote receiver of a line
break condition.
LCR[7]: Baud Rate Divisors Enable
Baud rate generator divisor (DLL and DLM) enable.
•Logic 0 = Data registers are selected (default).
•Logic 1 = Divisor latch registers are selected.
5.7 Modem Control Register (MCR) or General Purpose Outputs Control - Read/Write
The MCR register is used for controlling the serial/modem interface signals or general purpose inputs/outputs.
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REV. 1.0.0 WIRELESS UART CONTROLLER
MCR[0]: DTR# Output
The DTR# pin is a modem control output. If the modem interface is not used, this output may be used as a
general purpose output.
•Logic 0 = Force DTR# output HIGH (default).
•Logic 1 = Force DTR# output LOW.
MCR[1]: RTS# Output
The RTS# pin is a modem control output and may be used for automatic hardware flow control by enabled by
EFR bit-6. If the modem interface is not used, this output may be used as a general purpose output.
•Logic 0 = Force RTS# HIGH (default).
•Logic 1 = Force RTS# LOW.
MCR[2]: Reserved
OP1# is not available as an output pin on the enhanced UART. But it is available for use during Internal
Loopback Mode. In the Loopback Mode, this bit is used to write the state of the modem RI# interface signal.
MCR[3]: OP2# Output / INT Output Enable
This bit enables or disables the operation of INT, interrupt output. If INT output is not used, OP2# can be used
as a general purpose output. Also, if 16/68# pin selects Motorola bus interface mode, this bit must be set to
logic 0.
•Logic 0 = INT (A-B) outputs disabled (three state mode) and OP2# output set HIGH(default).
•Logic 1 = INT (A-B) outputs enabled (active mode) and OP2# output set LOW.
MCR[4]: Internal Loopback Enable
•Logic 0 = Disable loopback mode (default).
•Logic 1 = Enable local loopback mode, see loopback section and Figure 10.
MCR[7:5]: Reserved
For normal operation, these register bits should be ’0’.
5.8 Line Status Register (LSR) - Read Only
This register provides the status of data transfers between the UART and the host.
LSR[0]: Receive Data Ready Indicator
•Logic 0 = No data in receive holding register or FIFO (default).
•Logic 1 = Data has been received and is saved in the receive holding register or FIFO.
LSR[1]: Receiver Overrun Error Flag
•Logic 0 = No overrun error (default).
•Logic 1 = Overrun error. A data overrun error condition occurred in the receive shift register. This happens
when additional data arrives while the FIFO is full. In this case the previous data in the receive shift register
is overwritten. Note that under this condition the data byte in the receive shift register is not transferred into
the FIFO, therefore the data in the FIFO is not corrupted by the error.
LSR[2]: Receive Data Parity Error Tag
•Logic 0 = No parity error (default).
•Logic 1 = Parity error. The receive character in RHR does not have correct parity information and is suspect.
This error is associated with the character available for reading in RHR.
LSR[3]: Receive Data Framing Error Tag
•Logic 0 = No framing error (default).
•Logic 1 = Framing error. The receive character did not have a valid stop bit(s). This error is associated with
the character available for reading in RHR.
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WIRELESS UART CONTROLLER REV. 1.0.0
LSR[4]: Receive Break Error Tag
•Logic 0 = No break condition (default).
•Logic 1 = The receiver received a break signal (RX was LOW for at least one character frame time). In the
FIFO mode, only one break character is loaded into the FIFO.
LSR[5]: Transmit Holding Register Empty Flag
This bit is the Transmit Holding Register Empty indicator. The THR bit is set to a logic 1 when the last data byte
is transferred from the transmit holding register to the transmit shift register. The bit is reset to logic 0
concurrently with the data loading to the transmit holding register by the host. In the FIFO mode this bit is set
when the transmit FIFO is empty, it is cleared when the transmit FIFO contains at least 1 byte.
LSR[6]: THR and TSR Empty Flag
This bit is set to a logic 1 whenever the transmitter goes idle. It is set to logic 0 whenever either the THR or
TSR contains a data character. In the FIFO mode this bit is set to a logic 1 whenever the transmit FIFO and
transmit shift register are both empty.
LSR[7]: Receive FIFO Data Error Flag
•Logic 0 = No FIFO error (default).
•Logic 1 = A global indicator for the sum of all error bits in the RX FIFO. At least one parity error, framing error
or break indication is in the FIFO data. This bit clears when there is no more error(s) in any of the bytes in the
RX FIFO.
5.9 Modem Status Register (MSR) - Read Only
This register provides the current state of the modem interface input signals. Lower four bits of this register are
used to indicate the changed information. These bits are set to a logic 1 whenever a signal from the modem
changes state. These bits may be used for general purpose inputs when they are not used with modem
signals.
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REV. 1.0.0 WIRELESS UART CONTROLLER
MSR[0]: Delta CTS# Input Flag
•Logic 0 = No change on CTS# input (default).
•Logic 1 = The CTS# input has changed state since the last time it was monitored. A modem status interrupt
will be generated if MSR interrupt is enabled (IER bit-3).
MSR[1]: Delta DSR# Input Flag
•Logic 0 = No change on DSR# input (default).
•Logic 1 = The DSR# input has changed state since the last time it was monitored. A modem status interrupt
will be generated if MSR interrupt is enabled (IER bit-3).
MSR[2]: Delta RI# Input Flag
•Logic 0 = No change on RI# input (default).
•Logic 1 = The RI# input has changed from a LOW to HIGH, ending of the ringing signal. A modem status
interrupt will be generated if MSR interrupt is enabled (IER bit-3).
MSR[3]: Delta CD# Input Flag
•Logic 0 = No change on CD# input (default).
•Logic 1 = Indicates that the CD# input has changed state since the last time it was monitored. A modem
status interrupt will be generated if MSR interrupt is enabled (IER bit-3).
MSR[4]: CTS Input Status
CTS# pin may function as automatic hardware flow control signal input if it is enabled and selected by Auto
CTS (EFR bit-7). Auto CTS flow control allows starting and stopping of local data transmissions based on the
modem CTS# signal. A HIGH on the CTS# pin will stop UART transmitter as soon as the current character has
finished transmission, and a LOW will resume data transmission. Normally MSR bit-4 bit is the complement of
the CTS# input. However in the loopback mode, this bit is equivalent to the RTS# bit in the MCR register. The
CTS# input may be used as a general purpose input when the modem interface is not used.
MSR[5]: DSR Input Status
Normally this bit is the complement of the DSR# input. In the loopback mode, this bit is equivalent to the DTR#
bit in the MCR register. The DSR# input may be used as a general purpose input when the modem interface is
not used.
MSR[6]: RI Input Status
Normally this bit is the complement of the RI# input. In the loopback mode this bit is equivalent to bit-2 in the
MCR register. The RI# input may be used as a general purpose input when the modem interface is not used.
MSR[7]: CD Input Status
Normally this bit is the complement of the CD# input. In the loopback mode this bit is equivalent to bit-3 in the
MCR register. The CD# input may be used as a general purpose input when the modem interface is not used.
5.10 Scratch Pad Register (SPR) - Read/Write
This is a 8-bit general purpose register for the user to store temporary data.
5.11 Enhanced Mode Select Register (EMSR)
This register replaces SPR (during a Write) and is accessible only when FCTR[6] = 1.
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WIRELESS UART CONTROLLER REV. 1.0.0
EMSR[1:0]: Receive/Transmit FIFO Level Count (Write-Only)
When Scratchpad Swap (FCTR[6]) is asserted, EMSR bits 1-0 controls what mode the FIFO Level Counter is
operating in.
TABLE 12: SCRATCHPAD SWAP SELECTION
FCTR[6] EMSR[1] EMSR[0] Scratchpad is
0 X X Scratchpad
1 X 0 RX FIFO Level Counter Mode
1 0 1 TX FIFO Level Counter Mode
1 1 1 Alternate RX/TX FIFO Counter Mode
During Alternate RX/TX FIFO Level Counter Mode, the first value read after EMSR bits 1-0 have been
asserted will always be the RX FIFO Level Counter. The second value read will correspond with the TX FIFO
Level Counter. The next value will be the RX FIFO Level Counter again, then the TX FIFO Level Counter and
so on and so forth.
EMSR[3:2]: Reserved
For normal operation, these bits should be ’0’.
EMSR[5:4]: Extended RTS Hysteresis
TABLE 13: AUTO RTS HYSTERESIS
BIT-5 BIT-4 BIT-1 BIT-0 HYSTERESIS
(CHARACTERS)
0
0
0
0
0
0
0
0
0
0
1
1
0
1
0
1
0
±4
±6
±8
0
0
0
0
1
1
1
1
0
0
1
1
0
1
0
1
±8
±16
±24
±32
1
1
1
1
0
0
0
0
0
0
1
1
0
1
0
1
±40
±44
±48
±52
1
1
1
1
1
1
1
1
0
0
1
1
0
1
0
1
±12
±20
±28
±36
EMSR EMSR FCTR FCTR RTS#
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REV. 1.0.0 WIRELESS UART CONTROLLER
EMSR[6]: LSR Interrupt Mode
•Logic 0 = LSR Interrupt Delayed (for 16C550 compatibility, default). LSR bits 2, 3, and 4 will generate an
interrupt when the character with the error is in the RHR.
•Logic 1 = LSR Interrupt Immediate. LSR bits 2, 3, and 4 will generate an interrupt as soon as the character is
received into the FIFO.
EMSR[7]: Reserved
For normal operation, this bit should be ’1’.
5.12 FIFO Level Register (FLVL) - Read-Only
The FIFO Level Register replaces the Scratchpad Register (during a Read) when FCTR[6] = 1. Note that this is
not identical to the FIFO Data Count Register which can be accessed when LCR = 0xBF.
FLVL[7:0]: FIFO Level Register
This register provides the FIFO counter level for the RX FIFO or the TX FIFO or both depending on EMSR[1:0].
See Table 12 for details.
5.13 Baud Rate Generator Registers (DLL and DLM) - Read/Write
These registers make-up the value of the baud rate divisor. SEE”PROGRAMMABLE BAUD RATE
GENERATOR” ON PAGE 12.
5.14 Device Identification Register (DVID) - Read Only
This register contains the device ID (0x0A). Prior to reading this register, DLL and DLM should be set to 0x00.
5.15 Device Revision Register (DREV) - Read Only
This register contains the device revision information. For example, 0x01 means revision A. Prior to reading
this register, DLL and DLM should be set to 0x00.
5.16 Trigger Level Register (TRG) - Write-Only
User Programmable Transmit/Receive Trigger Level Register. If both the TX and RX trigger levels are used,
the TX trigger levels must be set before the RX trigger levels.
TRG[7:0]: Trigger Level Register
These bits are used to program desired trigger levels when trigger Table-D is selected. FCTR bit-7 selects
between programming the RX Trigger Level (a logic 0) and the TX Trigger Level (a logic 1).
5.17 RX/TX FIFO Level Count Register (FC) - Read-Only
This register is accessible when LCR = 0xBF. Note that this register is not identical to the FIFO Level Count
Register which is located in the general register set when FCTR bit-6 = 1 (Scratchpad Register Swap). It is
suggested to read the FIFO Level Count Register at the Scratchpad Register location when FCTR bit-6 = 1.
See Table 12.
FC[7:0]: RX/TX FIFO Level Count
Receive/Transmit FIFO Level Count. Number of characters in Receiver FIFO (FCTR[7] = 0) or Transmitter
FIFO (FCTR[7] = 1) can be read via this register. Reading this register is not recommended when transmitting
or receiving data.
5.18 Feature Control Register (FCTR) - Read/Write
FCTR[1:0]: RTS Hysteresis
User selectable RTS# hysteresis levels for hardware flow control application. After reset, these bits are set to
“0” to select the next trigger level for hardware flow control. See Table 13 for more details.
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WIRELESS UART CONTROLLER REV. 1.0.0
FCTR[3:2]: Reserved
For normal operation, these bits should be ’0’.
FCTR[5:4]: Transmit/Receive Trigger Table Select
See
TABLE 14: TRIGGER TABLE SELECT
BIT-5 BIT-4 TABLE
0 0 Table-A (TX/RX)
0 1 Table-B (TX/RX)
1 0 Table-C (TX/RX)
1 1 Table-D (TX/RX)
Table 10 for more details.
FCTR[6]: Scratchpad Swap
•Logic 0 = Scratch Pad register is selected as general read and write register. ST16C550 compatible mode.
•Logic 1 = FIFO Level Count register (Read-Only), Enhanced Mode Select Register (Write-Only). Number of
characters in transmit or receive FIFO can be read via scratch pad register when this bit is set. Enhanced
Mode Select Register is selected when it is written into.
FCTR[7]: Programmable Trigger Register Select
If using both programmable TX and RX trigger levels, TX trigger levels must be set before RX trigger levels.
•Logic 0 = Registers TRG and FC selected for RX.
•Logic 1 = Registers TRG and FC selected for TX.
5.19 Enhanced Feature Register (EFR)
EFR[3:0]: Reserved
For normal operation, these bits should be ’0’.
EFR[4]: Enhanced Function Bits Enable
Enhanced function control bit. This bit enables IER bits 4-7, ISR bits 4-5, FCR bits 4-5, and MCR bits 5-7 (MCR
bits 7-5 should remain at their default values of ’0’). After modifying any enhanced bits, EFR bit-4 can be set to
a logic 0 to latch the new values. This feature prevents legacy software from altering or overwriting the
enhanced functions once set. Normally, it is recommended to leave it enabled, logic 1.
•Logic 0 = modification disable/latch enhanced features. IER bits 4-7, ISR bits 4-5, FCR bits 4-5, and MCR
bits 5-7are saved to retain the user settings. After a reset, the IER bits 4-7, ISR bits 4-5, FCR bits 4-5, and
MCR bits 5-7 are set to a logic 0 to be compatible with ST16C550 mode (default).
•Logic 1 = Enables the above-mentioned register bits to be modified by the user.
EFR[5]: Reserved
For normal operation, this bit should be ’0’.
FCTR FCTR
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REV. 1.0.0 WIRELESS UART CONTROLLER
EFR[6]: Auto RTS Flow Control Enable
RTS# output may be used for hardware flow control by setting EFR bit-6 to logic 1. When Auto RTS is
selected, an interrupt will be generated when the receive FIFO is filled to the programmed trigger level and
RTS de-asserts HIGH at the next upper trigger level or hysteresis level. RTS# will return LOW when FIFO data
falls below the next lower trigger level. The RTS# output must be asserted (LOW) before the auto RTS can
take effect. RTS# pin will function as a general purpose output when hardware flow control is disabled.
•Logic 0 = Automatic RTS flow control is disabled (default).
•Logic 1 = Enable Automatic RTS flow control.
EFR[7]: Auto CTS Flow Control Enable
Automatic CTS Flow Control.
•Logic 0 = Automatic CTS flow control is disabled (default).
•Logic 1 = Enable Automatic CTS flow control. Data transmission stops when CTS# input de-asserts HIGH.
Data transmission resumes when CTS# returns LOW.
TABLE 15: UART RESET CONDITIONS
DLM, DLL DLM = 0x00 and DLL = 0x01. Only resets to these values during a power up.
They do not reset when the Reset Pin is asserted.
RHR Bits 7-0 = 0xXX
THR Bits 7-0 = 0xXX
IER Bits 7-0 = 0x00
FCR Bits 7-0 = 0x00
ISR Bits 7-0 = 0x01
LCR Bits 7-0 = 0x00
MCR Bits 7-0 = 0x00
LSR Bits 7-0 = 0x60
MSR Bits 3-0 = Logic 0
Bits 7-4 = Logic levels of the inputs inverted
SPR Bits 7-0 = 0xFF
EMSR Bits 7-0 = 0x80
FLVL Bits 7-0 = 0x00
EFR Bits 7-0 = 0x00
FCTR Bits 7-0 = 0x00
I/O SIGNALS
TX HIGH
RTS# HIGH
DTR# HIGH
RXRDY# HIGH
TXRDY# LOW
INT
(IRQ#)
Three-State Condition (16 mode)
HIGH (68 mode)
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WIRELESS UART CONTROLLER REV. 1.0.0
REGISTERS RESET STATE
RESET STATE
ABSOLUTE MAXIMUM RATINGS
Power Supply Range 4 Volts
Voltage at Any Pin GND-0.3V to 4V
Operating Temperature -40o to +85oC
Storage Temperature -65o to +150oC
Package Dissipation 500 mW
TYPICAL PACKAGE THERMAL RESISTANCE DATA (MARGIN OF ERROR: ± 15%)
Thermal Resistance (48-QFN) theta-ja =28oC/W, theta-jc = 10.5oC/W
ELECTRICAL CHARACTERISTICS
DC ELECTRICAL CHARACTERISTICS
O TO O O TO +85OC FOR INDUSTRIAL GRADE PACKAGE), VCC IS 2.25V TO 3.6V
SYMBOL PARAMETER
LIMITS
MIN MAX
LIMITS
MIN MAX
UNITS CONDITIONS
VILCKC CMOS/TTL Clock Input Low Level -0.3 0.4 -0.3 0.6 V
VIHCKC CMOS/TTL Clock Input High Level 2.0 VCC 2.4 VCC V
VILCKD
VIHCKD
Differential Clock Input Amplitude 200 200 mV
VIL Input Low Voltage -0.3 0.5 -0.3 0.7 V
VIH Input High Voltage 1.8 5.5 2.0 5.5 V
VOL Output Low Voltage
0.4
0.4 V
V
IOL = 4 mA
IOL = 2 mA
VOH Output High Voltage
1.8
2.0 V
V
IOH = -1 mA
IOH = -400 uA
IIL Input Low Leakage Current ±10 ±10 uA
IIH Input High Leakage Current ±10 ±10 uA
CIN Input Pin Capacitance 5 5 pF
ICC Power Supply Current 50 60 mA
XR18W750
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REV. 1.0.0 WIRELESS UART CONTROLLER
TA=0 70 C (-40
2.5V 3.3V
XR18W750
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WIRELESS UART CONTROLLER REV. 1.0.0
AC ELECTRICAL CHARACTERISTICS
UNLESS OTHERWISE NOTED: TA=0O TO 70OC (-40O TO +85OC FOR INDUSTRIAL GRADE PACKAGE), VCC=2.25 -
3.63V, 70 PF LOAD WHERE APPLICABLE
SYMBOL PARAMETER
LIMITS
2.5V ± 10%
MIN MAX
LIMITS
3.3V ± 10%
MIN MAX
UNIT
ECLK External Clock (CMOS/TTL or Differential) 16 16 MHz
TAS Address Setup Time (16 mode) 0 0 ns
TAH Address Hold Time (16 mode) 0 0 ns
TCS Chip Select Width (16 mode) 50 40 ns
TRD IOR# Strobe Width (16 mode) 50 40 ns
TDY Read Cycle Delay (16 mode) 50 40 ns
TRDV Data Access Time (16 mode) 45 35 ns
TDD Data Disable Time (16 mode) 25 25 ns
TWR IOW# Strobe Width (16 mode) 50 40 ns
TDY Write Cycle Delay (16 mode) 50 40 ns
TDS Data Setup Time (16 mode) 10 10 ns
TDH Data Hold Time (16 mode) 5 5 ns
TADS Address Setup (68 Mode) 0 0 ns
TADH Address Hold (68 Mode) 0 0 ns
TRWS R/W# Setup to CS# (68 Mode) 0 0 ns
TRDA Read Data Access (68 mode) 45 35 ns
TRDH Read Data Disable (68 mode) 25 25 ns
TWDS Write Data Setup (68 mode) 10 10 ns
TWDH Write Data Hold (68 Mode) 5 5 ns
TRWH CS# De-asserted to R/W# De-asserted (68 Mode) 5 5 ns
TCSL CS# Width (68 Mode) 50 40 ns
TCSD CS# Cycle Delay (68 Mode) 50 40 ns
TWDO Delay From IOW# To Output 50 50 ns
TMOD Delay To Set Interrupt From MODEM Input 50 50 ns
TRSI Delay To Reset Interrupt From IOR# 50 50 ns
TSSI Delay From Stop To Set Interrupt 1 1 Bclk
TRRI Delay From IOR# To Reset Interrupt 45 45 ns
TSI Delay From Stop To Interrupt 45 45 ns
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REV. 1.0.0 WIRELESS UART CONTROLLER
TINT Delay From Initial INT Reset To Transmit Start 824 824 Bclk
TWRI Delay From IOW# To Reset Interrupt 45 45 ns
TSSR Delay From Stop To Set RXRDY# 1 1 Bclk
TRR Delay From IOR# To Reset RXRDY# 45 45 ns
TWT Delay From IOW# To Set TXRDY# 45 45 ns
TSRT Delay From Center of Start To Reset TXRDY# 8 8 Bclk
TRST Reset Pulse Width 40 40 ns
Bclk Baud Clock 16X of data rate Hz
FIGURE 11. MODEM INPUT/OUTPUT TIMING
IOW #
RTS#
DTR#
CD#
CTS#
DSR#
INT
IOR#
RI#
TWDO
TMOD TMOD
TRSI
TMOD
Active
Active
Change of state Change of state
Active Active Active
Change of state Change of state
Change of state
Active Active
AC ELECTRICAL CHARACTERISTICS
UNLESS OTHERWISE NOTED: TA=0O TO 70OC (-40O TO +85OC FOR INDUSTRIAL GRADE PACKAGE), VCC=2.25 -
3.63V, 70 PF LOAD WHERE APPLICABLE
SYMBOL PARAMETER
LIMITS
2.5V ± 10%
MIN MAX
LIMITS
3.3V ± 10%
MIN MAX
UNIT
FIGURE 12. 16 MODE (INTEL) DATA BUS READ TIMING - PARALLEL MODE
TAS
TDD
TAH
TRD
TRDV
TDY
TDD
TRDV
TAH
TAS
TCS
Valid Address Valid Address
Valid Data Valid Data
A0-A2
CS#
IOR#
D0-D7
RDTm
TCS
TRD
FIGURE 13. 16 MODE (INTEL) DATA BUS WRITE TIMING - PARALLEL MODE
16Write
TAS
TDH
TAH
TWR
TDS
TDY
TDH
TDS
TAH
TAS
TCS
Valid Address Valid Address
Valid Data Valid Data
A0-A2
CS#
IOW#
D0-D7
TCS
TWR
XR18W750
38
WIRELESS UART CONTROLLER REV. 1.0.0
FIGURE 14. 68 MODE (MOTOROLA) DATA BUS READ TIMING - PARALLEL MODE
68Read
TADS
TRDH
TADHTCSL
TRDA
TCSD
TRWS
Valid Address Valid Address
Valid Data
A0-A2
CS#
R/W#
D0-D7
TRWH
Valid Data
FIGURE 15. 68 MODE (MOTOROLA) DATA BUS WRITE TIMING - PARALLEL MODE
68Write
TADS TADHTCSL
TWDS
TCSD
TRWS
Valid Address Valid Address
Valid Data
A0-A2
CS#
R/W#
D0-D7
TRWH
Valid Data
TWDH
XR18W750
39
REV. 1.0.0 WIRELESS UART CONTROLLER
FIGURE 16. RECEIVE READY & INTERRUPT TIMING [NON-FIFO MODE] - PARALLEL MODE
RX
RXRDY#
IOR#
INT
D0:D7
Start
Bit D0:D7
Stop
Bit D0:D7
TSSR
1 Byte
in RHR
Active
Data
Ready
Active
Data
Ready
Active
Data
Ready
1 Byte
in RHR
1 Byte
in RHR
TSSR TSSR
RXNFM
TRR TRR TRR
TSSR TSSR TSSR
(Reading data
out of RHR)
FIGURE 17. TRANSMIT READY & INTERRUPT TIMING [NON-FIFO MODE] - PARALLEL MODE
TX
TXRDY#
IOW#
INT*
D0:D7
Start
Bit D0:D7
Stop
Bit D0:D7
TWT
TXNonFIFO
TWT TWT
TWRI TWRI TWRI
TSRT TSRT TSRT
*INT is cleared when the ISR is read or when data is loaded into the THR.
ISR is read ISR is readISR is read
(Loading data
into THR)
IER[1]
enabled
XR18W750
40
WIRELESS UART CONTROLLER REV. 1.0.0
FIGURE 18. RECEIVE READY & INTERRUPT TIMING [FIFO MODE, DMA DISABLED] - PARALLEL MODE
RX
RXRDY#
IOR#
INT
D0:D7
S
TSSR
RXINTDMA#
RX FIFO fills up to RX
Trigger Level or RX Data
Timeout
RX FIFO drops
below RX
Trigger Level
FIFO
Empties
First Byte is
Received in
RX FIFO
D0:D7
SD0:D7TD0:D7
SD0:D7
S
TD0:D7
S
TTD0:D7
ST
Start
Bit
Stop
Bit
TRR
TRRI
TSSI
(Reading data out
of RX FIFO)
FIGURE 19. RECEIVE READY & INTERRUPT TIMING [FIFO MODE, DMA ENABLED] - PARALLEL MODE
RX
RXRDY#
IOR#
INT
D0:D7
S
TSSR
RXFIFODMA
RX FIFO fills up to RX
Trigger Level or RX Data
Timeout
RX FIFO drops
below RX
Trigger Level
FIFO
Empties
D0:D7
SD0:D7TD0:D7
SD0:D7
S
TD0:D7
S
TTD0:D7
ST
Start
Bit
Stop
Bit
TRR
TRRI
TSSI
(Reading data out
of RX FIFO)
XR18W750
41
REV. 1.0.0 WIRELESS UART CONTROLLER
FIGURE 20. TRANSMIT READY & INTERRUPT TIMING [FIFO MODE, DMA MODE DISABLED]
TX
TXRDY#
IOW#
INT*
TXDMA#
D0:D7
SD0:D7TD0:D7
SD0:D7
S
TD0:D7
S
TTD0:D7
ST
Start
Bit
Stop
Bit
TWRI
(Unloading)
(Loading data
into FIFO)
Last Data Byte
Transmitted
TX FIFO fills up
to trigger level TX FIFO drops
below trigger level
Data in
TX FIFO
TX FIFO
Empty
TWT
TSRT
TX FIFO
Empty
T
TS
TSI
ISR is read
IER[1]
enabled
ISR is read
*INT is cleared when the ISR is read or when TX FIFO fills up to the trigger level.
FIGURE 21. TRANSMIT READY & INTERRUPT TIMING [FIFO MODE, DMA MODE ENABLED] - PARALLEL MODE
TX
TXRDY#
IOW#
INT*
D0:D7
S
TXDMA
D0:D7
SD0:D7
TD0:D7
SD0:D7S
TD0:D7
S
TTD0:D7ST
Start
Bit
Stop
Bit
TWRI
T
(Unloading)
(Loading data
into FIFO)
Last Data Byte
Transmitted
TX FIFO fills up
to trigger level
TX FIFO drops
below trigger level
At least 1
empty location
in FIFO
TSRT
TX FIFO
Full
TWT
TSI
ISR Read ISR Read
*INT cleared when the ISR is read or when TX FIFO fills up to trigger level.
IER[1]
enabled
XR18W750
42
WIRELESS UART CONTROLLER REV. 1.0.0
PACKAGE DIMENSIONS (48 PIN QFN - 7 X 7 X 0.9 mm)
Note: The control dimension is in millimeter.
A0.031 0.039 0.80 1.00
A1 0.000 0.002 0.00 0.05
A3 0.006 0.010 0.15 0.25
D0.270 0.281 6.85 7.15
D2 0.201 0.209 5.10 5.30
b0.007 0.012 0.18 0.30
e0.0197 BSC 0.50 BSC
L0.012 0.020 0.30 0.50
XR18W750
43
REV. 1.0.0 WIRELESS UART CONTROLLER
INCHES MILLIMETERS
SYMBOL MIN MAX MIN MAX
REVISION HISTORY
DATE REVISION DESCRIPTION
February 2007 P1.0.0 Preliminary Datasheet.
March 2008 1.0.0 Final Datasheet.
44
NOTICE
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to
improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any
circuits described herein, conveys no license under any patent or other right, and makes no representation that
the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration
purposes and may vary depending upon a user’s specific application. While the information in this publication
has been carefully checked; no responsibility, however, is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the
failure or malfunction of the product can reasonably be expected to cause failure of the life support system or
to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless
EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has
been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately
protected under the circumstances.
Copyright 2008 EXAR Corporation
Datasheet March 2008.
Send your UART technical inquiry with technical details to hotline: uarttechsupport@exar.com.
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
XR18W750
WIRELESS UART CONTROLLER REV. 1.0.0
