XR16C872 Datasheet, PDF (6/60 Pages) Exar Corporation – DUAL UART WITH 1284 PARALLEL PORT AND PLUG-AND-PLAY CONTROLLER

XR16C872
DISCONTINUED
Name
Pin Type
Pin Description
IOCHRDY
20 OT24 Input/Output Channel Ready. IOCHRDY is a three state active high output
with an internal weak pull-up resistor. This pin goes low when 1284 parallel
port requires additional clock during a read or write cycle.
TC
91
I
Terminal Count. TC is an active high input during DMA cycle and when DACK#
is low to indicates data transfer is complete.
RESET
1
I
System Reset. Reset is an active high input. A 40ns minimum pulse will reset
the internal registers and outputs to the default state. The TX output is at logic
1 and RX input is internally held at logic 1 during reset. See XR16C872 Reset
Conditions for details.
XTAL1
76
I
Crystal Oscillator Input. A 22.1184 MHz crystal must be connected to this
input and XTAL2 pin to form an internal oscillator circuit which provides the
main clock to the the baud rate generators. An external clock of same
frequency may be used instead.
XTAL2
75
O Crystal Oscillator Output. The other side of the crystal is connected to this
pin to form an internal crystal oscillator.
EED
73 Bidir EED is a bi-drectional serial data bus to the external 93C46 EEPROM.
EECLK
72
O EECLK is a 500KHz clock output to the external EEPROM for serial data timing
reference.
EECS
71 Bidir EEPROM Chip Select. EECS is an active high output to the external EEPROM.
During Manual configuration mode, a logic 1 input will bypass the internal
divide-by-3 clock circuit to the two UARTs.
MAN#
74
I
Manual Configuration Select. MAN# is an active low input that enables S1-
S5 for selection of COM1-4 and LPT1-2 or in embedded applications.
1284 CONTROLLER INTERFACE
PD7-PD0
32-34 IOP14 Parallel Data Bus. PD0-PD7 are three-state bi-drectional data lines to the
37-41
parallel port. PD0 is the least significant bit with PD7 being the most
significant bit. PD0-PD7 are high current drive outputs and can connect to
the printer/parallel connector without external buffers.
ACK#
51 IP24 Acknowledge. ACK# is an active low input with with an internal weak pull-up.
It can be a general purpose input or line printer acknowledge signal. A logic
0 from the parallel/printer indicates successful data transfer to the print buffer.
AUTOFD#
PDIR
46 IOP14 AutoLineFeed. AUTOFD# is an active low tri-state with an internal weak pull-
up. It can be a general purpose I/O or automatic line feed. When this signal
is low the printer should automatically line feed after each printed line.
31
O Parallel Port Direction Indicator. PDIR indicates the operating direction of the
Rev. 1.00
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