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45 PCI Communication User Manual

Chapter 5 Pin Assignments and Wiring

5.2 Wiring

5.2.1 RS-232 Signal Wiring

Since the RS-232 interface is not strictly defined, many devices have their own con-

nection methods, and these may ignore some signal lines or lines reserved for other

functions. It is best to refer to the user manual of your device for installation instruc-

tions. You may find the following helpful.

In general, data terminal equipment (DTE) refers to a device that communicates with

data circuit-terminating equipment (DCE). DTE examples include PCs, terminals,

and some printers; whereas DCE examples include modems, digital service units

(DSUs), printers, and lab/factory equipment.

In some situations you may be able to get by with just three lines: data on TxD, a sig-

nal ground, and a handshaking line. Examples where this would work are printer or

plotter connections, troubleshooting, and situations where you require only one-wire

communication.

Table 5.15: Terminal or PC (DTE) Connections

DB-25 Male DB-25 Male or Female: Terminal

Pin Signal Pin Signal

2TxD3RxD

3RxD2TxD

4RTS5CTS

5CTS4RTS

6DSR20DTR

7GND7GND

20 DTR 6 DSR

8 DCD 8 DCD

Table 5.16: Modem Connections

DB-25 Male Modem (DCE)