Atari 8-Bit Computer

850 Interface Module

The 850 Interface has 4 serial ports on the back. When facing the back the serial ports are labeled 4 to 1 from left to right.

Pin	Description
Port 1	Port 2	Port 3	Port 4
1	Data Terminal Ready (DTR, Ready Out)
2	Carrier Detect (CRX, In)	Not Connected
3	Send Data (Out)
4	Receive Data (In)
5	Signal Ground
6	Data Set Ready (DSR, Ready In)	Not Connected
7	Request to Send (RTS, Out)	Not Connected	Request to Send (RTS, Out)
8	Clear to Send (CTS, In)	Not Connected
9	Not Connected	-8V

Description

Port 1

Port 2

Port 3

Port 4

Data Terminal Ready
(DTR, Ready Out)

Carrier Detect
(CRX, In)

Not Connected

Send Data
(Out)

Receive Data
(In)

Signal Ground

Data Set Ready
(DSR, Ready In)

Not Connected

Request to Send
(RTS, Out)

Not Connected

Request to Send
(RTS, Out)

Clear to Send
(CTS, In)

Not Connected

-8V

Pins 1 and 7 on port 4 are not computer-controlled and are always ON (+10V).