CM312 Datasheet, PDF (26/56 Pages) List of Unclassifed Manufacturers – Communications utilityModule

RS422 or RS485 Serial Port
You can change the mode switch to set the first port as RS422 or RS485. In this case, you must
connect CN3 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
TDX+, and connect RXD- to TXD-.
Note! Two 120-ohm termination resistors are provided on the utilityModule. Termination is
usually necessary on all RS-422 receivers and at the ends of the RS-485 bus. If the
termination resistor is required, it can be enabled by closing jumper JP8 5-6 for RxD
and/or 7-8 CTS.
RS422 and RS485 Mode Pinout
The following table gives the pinout of connector CN3 when RS422 or RS485 modes are enabled.
Table 9 Connector CN3 in RS422/485 Mode
CN3 Pin
Signal
Function
In/out
DB9
1
RTS-
Request to send (-)
Out
1
2
RTS+
Request to send (+)
Out
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
CTS-
Clear to send (-)
In
4
8
CTS+
Clear to send (+)
In
9
9,10
GND
Signal Ground
--
5
CM312 Quad Serial utilityModule
16
RTD Embedded Technologies, Inc.