COMPUTER TO TCS ASCII COMMUNICATIONS : Serial Port Connection

Jim Harwood

Revised March 18, 1999

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RS-232 Serial Port Connection

The protocol expected by the LSI-11 TCS from the remote computer is: no parity, 8 data bits, and 1 stop bit. Currently, the IRTF TCS is set to 9600 baud. You are advised to confirm the baud rate with the day crew.

Following is a description of the RS-232 signal lines at the remote computer end of the cable, as expected by the TCS computer.

Pin 2:

Transmit to TCS Receive (Pin 3).

Pin 3:

Receive from TCS Transmit (Pin 2).

Pin 4:

Request To Send (output) to TCS Clear To Send (Pin 5). Also jumpered to Pin 20, Data Terminal Ready. This signal is actively asserted and cleared by the remote computer, depending on whether or not the remote computer is ready to accept transmission from the TCS.

Pin 5:

Clear To Send (input) from TCS Request To Send (Pin 4). This signal is actively asserted and cleared by the TCS depending on whether or not the TCS is ready to accept transmission from the remote computer.

Pin 6:

Data Set Ready (input) from TCS Data Terminal Ready. Jumpered to Pin 8, Carrier Detect. This signal is permanently enabled while the TCS is on-line. It is not toggled as a handshake. The remote computer can use this signal to sense the presence of the TCS.

Pin 7:

Common. Connected to Pin 7 at the TCS.

Pin 8:

Carrier Detect (input). Jumpered to Pin 6. Senses Data Terminal Ready from TCS.

Pin 20:

Data Terminal Ready (output). Jumpered to Pin 4. Not connected to TCS. This signal is available for any equipment that wants to utilize DTR for handshaking.

 

TCS RS-232 Serial Port Cable

 

External(DTE)

 

DB25-S (Female)

Berg or 3M 40-pin

LSI-11/23 (DCE)

Braided Shield

1¾

·

 

 

 

 

 

 

Xmit

2

 

®

®

 

J

8

Rcv

Rcv

3

 

¬

¬

 

F

6

Xmit

Req To Send

4

 

®

®

 

T

16

Clear To Send

Clear To Send

5

 

¬

¬

 

V

18

Req To Send

Common

7

 

«

«

 

A

1

Common

Data Set Ready Carrier Detect

6
8

·
·

¬
Jumpered

¬
Jumpered

· ·

DD
BB

26
24

Data Terminal Ready
Carrier Detect

Jumpered

· ·

M
E

11
5

EIA Interlock