XR16C850CM-F Datasheet, PDF (6/56 Pages) Exar Corporation – 2.97V TO 5.5V UART WITH 128-BYTE FIFO

XR16C850
2.97V TO 5.5V UART WITH 128-BYTE FIFO
xr
REV. 2.3.1
NAME
44-PIN
PLCC
48-PIN
TQFP
TYPE
DESCRIPTION
LPT2#
26
22 O Line Printer Port-2 Decode Logic Output (active low) - This pin functions as the PC
standard LPT-2 printer port address decode logic output, see Table 1. During Intel
Bus Mode, LPT2# becomes DDIS#/D12.
MODEM OR SERIAL I/O INTERFACE
TX
13
8
O Transmit Data or wireless infrared transmit data. This output is active low in normal
standard serial interface operation (RS-232, RS-422 or RS-485) and active high in
the infrared mode. Infrared mode can be enabled by connecting pin ENIR to VCC
or through software selection after power up.
RX
11
7
I Receive Data or wireless infrared receive data. Normal received data input idles at
logic 1 condition and logic 0 in the infrared mode. The wireless infrared pulses are
applied to the decoder. This input must be connected to its idle logic state in either
normal, logic 1, or infrared mode, logic 0, else the receiver may report “receive
break” and/or “error” condition(s).
RTS#
36
32 O Request to Send or general purpose output (active low). This port may be used for
automatic hardware flow control, see EFR bit-6, MCR bit-1, FCTR bits 0-1 and IER
bit-6. RTS# output must be asserted before auto RTS flow control can start. If this
pin is not needed for modem communication, then it can be used as a general I/O.
If it is not used, leave it unconnected.
CTS#
40
38
I Clear to Send or general purpose input (active low). If used for automatic hardware
flow control, data transmission will be stopped when this pin is de-asserted and will
resume when this pin is asserted again. See EFR bit-7, MCR bit-2 and IER bit-7. If
this pin is not needed for modem communication, then it can be used as a general
I/O. If it is not used, connect it to VCC.
DTR#
37
33 O Data Terminal Ready or general purpose output (active low). If this pin is not
needed for modem communication, then it can be used as a general I/O. If it is not
used, leave it unconnected.
DSR#
41
39
I Data Set Ready input or general purpose input (active low). If this pin is not
needed for modem communication, then it can be used as a general I/O. If it is not
used, connect it to VCC.
CD#
42
40
I Carrier Detect input or general purpose input (active low). If this pin is not needed
for modem communication, then it can be used as a general I/O. If it is not used,
connect it to VCC.
RI#
43
41
ANCILLARY SIGNALS
XTAL1
18
14
I Ring Indicator input or general purpose input (active low). If this pin is not needed
for modem communication, then it can be used as a general I/O. If it is not used,
connect it to VCC.
I Crystal or external clock input. See Figure 7 for typical oscillator connections.
Caution: this input is not 5V tolerant.
XTAL2
19
15 O Crystal or buffered clock output. See Figure 7 for typical oscillator connections.
SEL
34
36
I PC Mode Select (active low). When this input is at logic 0, it enables the on-board
chip select decode function according to PC ISA bus COM[4:1] and IRQ[4,3] port
definitions. See Table 3 for details. This pin has an internal 100kΩ pull-up resistor.
This pin is not available on the 40 pin PDIP packages which operate in the Intel
Bus Mode only.
6