IBM CMX58886CX user manual Serial Port in RS-422/485 Mode, Pin Signal Function In/Out DB-9

RS-422 and RS-485 Mode Pinout

Table 21 provides the serial port connector pinout when RS-422 or RS-485 modes are enabled.

Table 21 Serial Port in RS-422/485 Mode

Pin	Signal	Function	In/Out	DB-9
1	—	Data Carrier Detect	—	1
2	—	Data Set Ready	—	6
3	RXD–	Receive Data (–)	in	2
4	TXD+	Transmit Data (+)	out	7
5	TXD–	Transmit Data (–)	out	3
6	RXD+	Receive Data (+)	in	8
7	—	Reseved	—	4
8	—	Reseved	—	9
9,10	GND	Signal Ground	out	5

Facing the serial port connector, the pinout is:

9	7	5	3	1
GND	Rsvd	TXD-	RXD-	Rsvd
GND	Rsvd	RXD+	TXD+	Rsvd
10	8	6	4	2

Note When using the serial port in RS-485 mode, the serial transmitters are enabled and disabled under software control. The transmitters are enabled by manipulating the Request To Send (RTS*) signal of the serial port controller. This signal is controlled by writing bit 1 of the Modem Control Register (MCR) as follows:

•If MCR bit 1 = 1, then RTS* = 0, and serial transmitters are disabled

•If MCR bit 1 = 0, then RTS* = 1, and serial transmitters are enabled

Note For more information on the serial port registers, including the MCR, refer to the Serial Port Programming reference on page 99.

36 CMX58886CX cpuModule BDM-610000050 Rev A