Table 6.2: Modem Connections
For DTE to DCE connections, use a straight through cable (i.e., you don't have to reverse lines 2 and 3, lines 4 and
5, and lines 6 and 20 since, in general, the DCE RS-232 interfaces are reversed themselves).
Table 6.3: Terminal without Handshake
Therefore, if you are not using CTS, RTS, DSR,DTR and DCD signals, short pins 4 and 5 together, and please short
pins 6, 8,and 20 together.
6.2 RS-422 Signal Wiring
The RS-422 interface wiring is based on one-to-one principles. The transmit lines on one side connect to the receive
lines on the other side, and vice versa. With RS-422, you can transmit and receive data simultaneously (full duplex).
The connections are as follows:
Table 6.4:RS-422 DB9 Pin Assignment
Terminator Resistors Setup
The signals DSR, DTR and DCD are shorted internally on the PCM-24D2R4/24D4R4 cards when operating in
RS-422 mode. A user can solder in termination resistors if necessary for impedance matching. The card has two
mounting spaces for termination resistors, but no resistors are installed at the factory. Each pair of signal lines has a
separate resistor (RxD+/-, TxD+/-).
MOS-1120/MOS-1121 User Manual 8
