XR16C872CQ EXAR [Exar Corporation], XR16C872CQ Datasheet - Page 6

• Manufacturer Part Number: XR16C872CQ
• Description: DUAL UART WITH 1284 PARALLEL PORT AND PLUG-AND-PLAY CONTROLLER
• Manufacturer: EXAR [Exar Corporation]

XR16C872
1284 CONTROLLER INTERFACE
Name
IOCHRDY
TC
RESET
XTAL1
XTAL2
EED
EECLK
EECS
MAN#
PD7-PD0
ACK#
AUTOFD#
PDIR
Rev. 1.00
37-41
32-34
Pin
73
72
71
20
91
76
75
74
51
46
31
1
IOP14
IOP14
IP24
OT24
Type
Bidir
Bidir
O
O
O
I
I
I
I
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.
Terminal Count. TC is an active high input during DMA cycle and when DACK#
is low to indicates data transfer is complete.
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.
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.
Crystal Oscillator Output. The other side of the crystal is connected to this
pin to form an internal crystal oscillator.
EED is a bi-drectional serial data bus to the external 93C46 EEPROM.
EECLK is a 500KHz clock output to the external EEPROM for serial data timing
reference.
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.
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.
Parallel Data Bus. PD0-PD7 are three-state bi-drectional data lines to the
significant bit. PD0-PD7 are high current drive outputs and can connect to
the printer/parallel connector without external buffers.
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.
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.
parallel port. PD0 is the least significant bit with PD7 being the most
Parallel Port Direction Indicator. PDIR indicates the operating direction of the
DISCONTINUED
6
Pin Description
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