IBM BDM-610000049 RS-422 or RS-485 Serial Port, Full-Duplex Connections, Half-Duplex RS-485 Mode

Facing the serial port’s connector pins, the pinout is:

9 7 5 3 1

GND

DTR

TXD

RXD

DCD

GND

RI

CTS

RTS

DSR

10 8 6 4 2

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–.

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),JP2 for Serial Port 2 (COM2), JP11 for Serial Port 3 (COM3), and JP13 for Serial Port 4 (COM4).

When using full-duplex (typically in RS-422 mode), connect the ports as shown in Table 19.

Table 19 Full-Duplex Connections

Port 1	Port 2
RXD+	TXD+
TXD+	RXD+
RXD–	TXD–
TXD–	RXD–

When using half-duplex in RS-485 mode, connect the ports as shown in Table 20.

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–

38 CMX158886 cpuModule BDM-610000049 Rev G