User`s manual

RS422 or RS485 Serial Port

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

connect CN8 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 CN8 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 second se-

rial 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 JP4.

Connector CN8 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