ST16C552 Exar Corporation, ST16C552 Datasheet - Page 5

• Manufacturer Part Number: ST16C552
• Description: DUAL UART WITH 16-BYTE FIFO AND PARALLEL PRINTER PORT
• Manufacturer: Exar Corporation

SYMBOL DESCRIPTION
-IOR
-IOW
PD7-PD0
PE
RDOUT
-RESET
-RXRDY A/B
Symbol
Rev. 3.40
46-53
9,61
Pin
37
36
67
44
39
Signal Type
I/O
O
O
I
I
I
I
trailing edge of -IOR (end of the external CPU read cycle).
Read strobe.- A logic 0 transition on this pin will place the
contents of an Internal register defined by address bits A0-
A2 for either UART channels A/B or A0-A1 for the printer
port, onto D0-D7 data bus for a read cycle by an external
CPU.
Write strobe.- A logic 0 transition on this pin will transfer the
data on the internal data bus (D0-D7), as defined by either
address bits A0-A2 for UART channels A/B or A0-A1 for the
printer port, into an internal register during a write cycle from
an external CPU.
Printer Data port (Bi-directional three state) - These pins are
the eight bit, three state data bus for transferring information
to or from an external device (usually a printer). D0 is the
least significant bit. PD7-PD0 are latched during a write
cycle (output mode).
Paper Empty - General purpose input or line printer paper
empty (Internal pull-up). This pin can be connected to
provide a printer out of paper indication.
Read Out (active high) - This pin goes to a logic 1 when the
external CPU is reading data from the 552/552A. This signal
can be used to enable/disable external transceivers or other
logic functions.
Master Reset (active low) - a logic 0 on this pin will reset the
internal registers and all the outputs. The UART transmitter
output and the receiver input will be disabled during reset
time. (See ST16C552/552A External Reset Conditions for
initialization details.)
Receive Ready A/B (active low). This function is associated
with the dual channel UARTs and provide the RX FIFO/
RHR status for individual receive channels (A-B). A logic 0
indicates there is receive data to read/unload, i.e., receive
ready status with one or more RX characters available in the
FIFO/RHR. This pin is a logic 1 when the FIFO/RHR is
empty or when the programmed trigger level has not been
5
Pin Description
ST16C552/552A