User`s manual

RS422 or RS485 Serial Port

You may use Setup to configure the first serial port as RS422 or RS485. In this case, you must con-

nect CN7 to an RS422 or RS485 compatible device.

When using RS422 or RS485 mode, you can use the port 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-.

RS422andRS485ModePinout

The following table gives the pinout of connector CN7 when RS422 or RS485 modes are enabled.

Facing the connector pins, the pinout is:

Note when using RS422 or RS485 Mode

When using the serial port in RS422 or RS485 mode, the serial transmitters are enabled and disabled

under software control; the receivers are always enabled.

The transmitters are enabled by manipulating the Request To Send (RTS*) signal of the first serial

port controller. This signal is controlled by writing bit 1 of the Modem Control Register (MCR) as

follows:

NOTE!

A 120 ohm termination resistors is provided on the cpuModule. Termi-

nation is usually necessary on all RS422 receivers and at the ends of the

RS485 lines.

If the termination resistor is required, it can be enabled by closing jump-

er JP3.

Connector CN7 in RS422 or RS485 Mode

Pin Signal Function in/out DB9

1 Reserved -- 1

2 Reserved -- 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 Reserved -- 4

8 Reserved -- 9

9,10 gnd Signal ground -- 5

9 7 5 3 1

GND Rsvd TXD- RXD- Rsvd

GND Rsvd RXD+ TXD+ Rsvd

10 8 6 4 2