RS-422 Cabling Pin Outs for PortServer TS, ConnectPort LTS and Digi One SP Products

General EIA-422 Cable Information

This section applies to Digi products equipped with EIA-422 asynchronous 
interfaces.

Physical Cable Characteristics

EIA-422 interface cables should be shielded twisted-pair cables. Each 
signal requires two leads (one twisted pair of wires) to complete a balanced 
voltage digital circuit. The shield should be connected to the Chassis 
Ground of the devices at both ends of the interface cable.

Interface Signaling

The EIA-422 interface provides four signals: Transmitted Data (TxD), 
Received Data (RxD), Request To Send (RTS) and Clear To Send (CTS). 
The functions of these signals are identical to their EIA-232 counterparts.

Grounding Requirements

EIA-422 interface cables must provide a ground path between the devices 
to be connected. This ensures the integrity of data transfers and control 
signals. This should be connected to the Chassis Ground of each device. 
Digi recommends using the cable shield for this purpose.

Digi EIA-422 Connector Wiring

A terminal, a serial printer, or a serial port for another computer usually 
functions as a DTE device. The Digi adapter is also a DTE device. To 
connect a DTE device to another DTE device a null modem cable or 
adapter must be used.

Two wires (one twisted pair) are required for each signal, a positive lead 
("+"), and a negative lead ("-"). The "+" leads at one end of the cable must 
be connected to the "+" leads at the other end, and the "-" leads at one end 
must be connected to the "-" leads at the other end.

Incorrect wiring could result in damage to the connected devices. The 
following table shows the pin configurations for the EIA-422 versions of 
Digi DB-9, DB-25, and RJ-45 connectors:


 

 
8-Pin Option for PortServer TS 8/16 MEI Models only:


EIA-422 Software Handshaking (XON/XOFF) Cable

Use the chart below as a guide for EIA-422 wiring:


 

EIA-422 Hardware Handshaking (Ready/Busy) Cable

Use the following table as a guide for EIA-422 wiring.


 

EIA-422 DTE to DCE (Modem) Cable

Use the chart below as a guide for EIA-422 modem wiring: