### EIA 422 Asynchronous Interface

This section applies to AccelePort adapters equipped with EIA-422 asynchronous interfaces.

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.

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.

A DTE device is a terminal, serial printer, serial port for another computer, etc. 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.

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 and DB-25 connectors.

#### DB-9 and DB-25 Connector Wiring for Digi EIA-422 Adapters

Signal | Description | DB-9 Pin | DB-25 Pin
--- | --- | --- | ---
TxD+ | Transmitted Data (+) | 8 | 2
TxD- | Transmitted Data (-) | 9 | 14
RxD+ | Received Data (+) | 6 | 3
RxD- | Received Data (-) | 7 | 16
RTS+ | Request To Send (+) | 2 | 4
RTS- | Request To Send (-) | 3 | 19
CTS+ | Clear To Send (+) | 4 | 5
CTS- | Clear To Send (-) | 5 | 13
GND | Chassis Ground | Shell | 1, 7, Shell

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