rtd cpuModule CMX47786HX, User Manual

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CMX47786HX RTD Embedded Technologies, Inc.
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RS422 and RS485 Mode Pinout
The following table gives the pinout of the serial port connector when RS422 or RS485 modes are
enabled.
Facing the serial port connector, the pinout is:
Table 10: Serial Port in RS-422/485 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 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 RS485 Mode
When using the serial port in RS485 mode, the serial transmitters are
enabled and disabled under software control. The transmitters are en-
abled 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
For more information on the serial port registers, including the MCR,
please refer to a standard PC-AT hardware reference for the 16550-type
UART.