A

EIA-232-D Interconnections

Figure A-2 shows a way of wiring an EIA-232-D connector to enable a computer to connect to a basic terminal with only three lines. This is feasible because most terminals have a DTR signal that is ON, and which can be used to pull up the CTS, DCD, and DSR signals.

Two of these connectors wired back-to-back can be used. In this implementation, however, diagnostic messages that might otherwise be generated do not occur because all the handshaking is bypassed. In addition, the TX and RX lines may have to be crossed since TX from a terminal is outgoing but the TX line on a modem is an incoming signal.

 

EIA-232-D CONNECTOR

GND

1

TxD

2

RxD

3

RTS

4

CTS

5

DSR

6

GND

7

DCD

8

 

. . . .

DTR

20

Figure A-2. Minimum EIA-232-D Connection

A-6

Page 78
Image 78
Motorola MVME177 manual Figure A-2. Minimum EIA-232-D Connection