XR19L220_07 Datasheet, PDF (3/43 Pages) Exar Corporation – SINGLE CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER

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PIN DESCRIPTIONS
Pin Descriptions
XR19L220
SINGLE CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
NAME
40-QFN
PIN#
TYPE
DESCRIPTION
DATA BUS INTERFACE (CMOS/TTL Voltage Levels)
A2
23
I _{Address bus lines [2:0]. These 3 address lines select one of the internal registers in the}
A1
24
UART during a data bus transaction.
A0
25
D7
8
I/O _{Data bus lines [7:0] (bidirectional).}
D6
7
D5
5
D4
38
D3
37
D2
36
D1
35
D0
34
IOR#
19
I _{When I/M# pin is HIGH, the Intel bus interface is selected and this input becomes read}
(NC)
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#
17
(R/W#)
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#
9
I _{This input is chip select (active LOW) to enable the device.}
INT
(IRQ#)
26
O _{When I/M# pin is HIGH, it selects Intel bus interface and this output become the active}
(OD) HIGH device interrupt output. This output is enabled through the software setting of MCR[3]:
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. An external pull-up resistor is required for proper opera-
tion. MCR[3] must be set to a logic 0 for proper operation of the interrupt.
MODEM OR SERIAL I/O INTERFACE (EIA-232/RS-232 Voltage Levels)
TXD
10
O _{UART Transmit Data. The TX signal will be LOW (< -5.0V) during reset or idle (no data).}
RXD
2
I _{UART Receive Data. The RX data input must idle LOW (< -3.0V).}
RTS
11
O _{UART Request-to-Send or general purpose output. This output must be asserted prior to}
using auto RTS flow control, see EFR[6], MCR[1] and IER[6].
CTS
1
I _{UART Clear-to-Send or general purpose input. It can be used for auto CTS flow control,}
see EFR[7], MSR[4] and IER[7]. This input has an internal pull-down resistor and can be left
unconnected when not used.
DTR
12
O _{UART Data-Terminal-Ready or general purpose output.}
DSR
3
I _{UART Data-Set-Ready or general purpose input. This input has an internal pull-down resis-}
tor and can be left unconnected when not used.
3