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BDM-610000075 Rev B Chapter 3: Connecting the cpuModule 35
RS-422 and RS-485 Mode Pinout
Table 19 provides the serial port connector pinout when RS-422 or RS-485 modes are enabled.
Facing the serial port connector, the pinout is:
Table 19 Serial Port in RS-422/485 Mode
Pin Signal Function In/Out DB-9
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 — Reseved — 4
8 — Reseved — 9
9,10 GND Signal Ground out 5
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 in Appendix D.