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XR16C872

Dual UART with 1284 Parallel Port and Plug-and-Play Controller

Exar Corporation 

Preliminary

XR16C872

PIN DESCRIPTION (CONT'D)

Symbol

Pin # Type Pin Description

PDIR

31

O

Parallel Port Direction Indicator. PDIR indicates the operating direction of the

parallel port. An output logic 0 indicates the parallel port is operating as an

output port and a logic 1 indicates it is an input port.

BUSY

50

IP24 BUSY is an active high printer busy indicator or general purpose input.

Generally, it is used as an input from the printer and a logic 1 indicates it is not

ready. The input has an internal weak pull-up resistor.

ERR#

52

IP24 ERR# is printer error indicator or a general purpose input. Generally, it is

used as an input from the printer and a logic 0 indicates it has an error

condition. The input has a weak internal pull-up resistor.

INIT#

45 IOP14 INIT# is a printer initialization signal or a general purpose output. Generally, it

is used with the printer (active low) for system initialization or reset. The pin is

a tri-state output and has an internal weak pull-up resistor.

PE

49

IP24 PE is a signal from the printer indicating a paper empty condition or general

purpose input. Generally, it is used with a printer and a logic 1 indicates the

printer is out of paper. This input has an internal weak pull-up resistor.

SELECT

48

IP24 SELECT is the printer select status indicator to the host or general purpose

input. Normally this pin is connected to a printer output and a logic 0 indicates

the ready status of the printer, i.e., on-line and/or on-line and ready condiftion.

This pin has an internal weak pull-up resistor.

SELCTIN#

44 IOP14 SELCTIN# is a select signal to the printer or general purpose I/O pin. This pin

can be read via bit-3 in the printer command register, or written via bit-3 in the

printer control register. Normally this signal is connected to a printer to select

the printer with an active low signal. The pin is tri-state output and has an

internal weak pull-up resistor.

STROBE#

47 IOP14 STROBE# is a data strobe output or general purpose I/O pin. Normally this

output is connected to a printer and indicates that valid data is available on

the data bus (PD0-PD7). The pin is a tri-state output with an intenal weak

pull-up resistor.

MODEM OR SERIAL PORT INTERFACE

RXA, RXB 63,53

I

Receive Data A/B. Serial receive data or IR pulses input to UART channel A

and B. The RX signal to the UART should be a logic 1 state during reset, idle

(no data) and sleep mode. During the local loop-back mode, the RX input pins

are disabled and TX data is internally connected to the UART RX Inputs. In the

IR mode, this input is normally at logic 0.

TXA, TXB 64,54

O

Transmit Data A/B. Serial transmit data or IR pulses output from channel A

and B. The normal output is a logic 1 for serial data during reset, idle (no

data), sleep mode, or when the transmitter is disabled. During the local loop-

back mode, the TX output pin is held at logic 1and internally it connects to RX

input. In IR mode, the output changes to a logic 0 after it is enabled (MCR

bit 5=1).

Rev. P1.00

7

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