Instruction manual

Chapter 2 Installation 27
RS-422
RS-485
RS-232/422/485 serial port connections
(COMA, COMB)
Pin assignments
The following table shows the pin assignments for the card's RS-
232 and RS-422/485 (COMB) serial port connectors:
RS-232 (COMA, COMB) RS-422/485 (COMB)
Pin Signal Pin Signal
1 DCD 1 TX- (DTE)
2 RX 2 TX+ (DTE)
3 TX 3 RX+ (DTE)
4 DTR 4 RX- (DTE)
5 GND 5 Ground
6 DSR 6 RTS-
7 RTS 7 RTS+
8 CTS 8 CTS-
9 RI 9 CTS-
RS-422 signal wiring
RS-422 is used for long-distance point-to-point connections. RS-
422 originally used four wires for one-way communication (with
devices such as display terminals or printer) but was later adopted