User`s manual

38 CMX34GS cpuModule BDM-610000082 Rev A
RS-485 Mode Pinout
Table 17 provides the serial port connector pinout when RS-482 mode is enabled
Facing the serial port connector, the pinout is:
Table 17 Serial Port in RS-485 Mode
Pin Signal Function In/Out DB-9
1D–Data (–) in/out1
2—Reserved —6
3D+Data (+) in/out2
4—Reserved —7
5—Reserved —3
6—Reserved —8
7—Reserved —4
8—Reseved —9
9,10 GND Signal Ground out 5
97531
GND Rsvd Rsvd D+ D-
GND Rsvd Rsvd Rsvd Rsvd
10 8 6 4 2
WARNING The pinout of the COM ports in RS-485 mode is not compatible with previous generations
of RTD cpuModules.
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 in Appendix D.