XR19L400
3
REV. 1.0.3
SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER
PIN DESCRIPTIONS
Pin Descriptions
NAME
40-QFN
PIN#
TYPE
DESCRIPTION
DATA BUS INTERFACE (CMOS/TTL Voltage Levels)
A2
A1
A0
38
39
40
I
Address bus lines [2:0]. These 3 address lines select one of the internal registers in the
UART during a data bus transaction.
D7
D6
D5
D4
D3
D2
D1
D0
8
7
6
5
4
3
2
1
I/O Data bus lines [7:0] (bidirectional).
IOR#
(NC)
15
I
When I/M# 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 I/M# pin is LOW, the Motorola bus interface is selected and this input is not used.
IOW#
(R/W#)
14
I
When I/M# 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 trans-
fers the data byte on the data bus to an internal register pointed by the address lines.
When I/M# pin is LOW, the Motorola bus interface is selected and this input becomes read
(HIGH) and write (LOW) signal.
CS#
(CS#)
9
I
This input is the chip select (active low) for the UART in both the Intel and Motorola bus
modes.
INT
(IRQ#)
37
O
(OD)
When I/M# pin is HIGH, it selects Intel bus interface and this output become the active
HIGH interrupt output. This output is enabled through the software setting of MCR[3]. This
output is set to the active mode when MCR[3] is set to a logic 1, and set to the three state
mode when MCR[3] is set to a logic 0. See MCR[3].
When I/M# pin is LOW, it selects Motorola bus interface and this output becomes the active
LOW, open-drain interrupt output for both channels. An external pull-up resistor is required
for proper operation. MCR[3] must be set to a logic 0 for proper operation of the interrupt.
SERIAL I/O INTERFACE (RS-485/RS-485 Voltage Levels)
TX+
TX-
32
30
O
Differential UART Transmit Data.
RX+
RX-
28
27
I
Differential UART Receive Data.
ANCILLARY SIGNALS (CMOS/TTL Voltage Levels)
HALF/
FULL#
34
I
Half-duplex or full-duplex mode select. This pin is sampled upon power-up.
When HALF/FULL# is HIGH, half-duplex mode is enabled.
When HALF/FULL# is LOW, full-duplex mode is enabled.
After power-up, FCTR bit-3 can select between the half-duplex or full-duplex modes.
XTAL1
12
I
Crystal or external clock input.