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DESCRIPTION
FEATURES
PIN CONFIGURATION
North Star HSIO-4
PROGRAMMABLE COMMUNICATION INTERFACE
ThepPD8251 Universal Synchronous/Asynchronous Receiver/Transmitter (USART) is
designed for microcomputer systems data communications. The USART is used as a
peripheral and is programmed by the pPD8080 or other processor to communicate in
commonly used serial data transmission techniques including IBM Bi-Sync. The USART
receives serial data streams and converts them into parallel data characters for the
processor. While receiving serial data, the USART w ill also accept data characters from
the processor in parallel format, convert them to serial format and transmit. The USART
w ill signal the processor when it has completely received or transmitted a character and
requires service. Complete USART STATUS including data format errors and control
signals such asTxE and SYNDET is available to the processor at any time.
•
Asynchronous or Synchronous Operation
— Asynchronous:
5-8 Bit Characters
Clock Rate — 1, 16 or 64 x Baud Rate
Break Character Generation
Select 1, 1-1/2, or 2 Stop Bits
False Start B it Detector
— Synchronous:
5-8 Bit Characters
Internal or External Character Synchronization
Automatic Sync Insertion
Single or Double Sync Characters
•
Baud Rate — Synchronous — DC to 56K Baud
— Asynchronous — DC to 9.6K Baud
•
Full Duplex, Double Buffered Transmitter and Receiver
•
Parity, Overrun and Framing Flags
•
Fully Compatible w ith 8080
•
A ll Inputs and Outputs are TTL Compatible
•
Single+5 V o lt Supply
•
Separate Device, Receive and Transmit T T L Clocks
•
28 Pin Plastic DIP Package
•
N-Channel MOS Technology
76
D i
°0
Oj Do
vcc
C/D
R D
RxC
W R
cs
DTR
CLK
RESET
RTS
TTc
TxD
DSR
RxC
RxD
RESET
Rx R DY
TxRDY
CLK
DSR
O T
TxD
r
SYNDET Sync Detect
TxE
RTS
CT3
CTS
TxE
v Cc
SYNDET
G N D
TxRDY
User/Technical Manual
fj. PD8251
PIN NAMES
Data Bus ( 8 bus)
Control or Data i s to be Written or Read
Read Data Command
Wnte Data or Control Command
Chip Enable
Clock Pulse (TTL)
Reset
Transmitter Clock ITTL)
Transmitter Data
Receiver Clock (TTL)
Receiver Data
Receiver Ready (has character f o r 8080)
Transmitter Ready (ready for char from 8080)
Data Set Ready
Data Terminal Ready
Request to Send Data
Clear to Send Data
Transmitter Empty
♦5 Volt Supply
Ground
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