cmd6686gx manual - RTD Embedded Technologies, Inc.

Connector CN8 in RS-422/485 Mode
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
Facing the serial port’s connector pins, the pinout is:
9 7 5 3 1
GND Rsvd TXD- RXD- Rsvd
GND Rsvd RXD+ TXD+ Rsvd
10 8 6 4 2
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 first serial port controller or by I/O
port 0x18. This signal is controlled by writing bit 1 of the Modem
Control Register (MCR) or writting toI/O port 0x18 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
• If Port 0x18h OR 0xCh then transmitters always on
• If Port 0x18h AND 0x3h then transmitters under
RTS* control
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.
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