IBM CMX58886CX - Manual (Page 43)

BDM-610000050 Rev A Chapter 3: Connecting the cpuModule 35
Facing the serial port’s connector pins, the pinout is:
RS-422 or RS-485 Serial Port
You may use Setup to configure the serial ports as RS-422 or RS-485. In this case, you must connect the serial
port to an RS-422 or RS-485 compatible device.
When using RS-422 or RS-485 mode, you can use the serial ports in either half-duplex (two-wire) or full-duplex
(four-wire) configurations. For half-duplex (2-wire) operation, you must connect RXD+ to TXD+, and connect
RXD– to TXD–.
When using full-duplex (typically in RS-422 mode), connect the ports as shown in Table 19.
When using half-duplex in RS-485 mode, connect the ports as shown in Table 20.
9 7 5 3 1
GND DTR TXD RXD DCD
GND RI CTS RTS DSR
10 8 6 4 2
Note The cpuModule has a 120 Ω termination resistor. Termination is usually necessary on all RS-422
receivers and at the ends of the RS-485 bus.
Note If required, the termination resistor can be enabled by closing jumper JP1 for Serial Port 1 (COM1)
or JP2 for Serial Port 2 (COM2).
Table 19 Full-Duplex Connections
Port 1 Port 2
RXD+ TXD+
TXD+ RXD+
RXD– TXD–
TXD– RXD–
Table 20 Half-Duplex RS-485 Mode
From To
Port 1 TXD+ Port 1 RXD+
Port 1 TXD– Port 1 RXD–
Port 1 TXD+ Port 2 RXD+
Port 1 RXD– Port 2 TXD–