Moxa Technologies Industio C114HI, Manual

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RS-232/RS-422/RS-482 Programming
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Chapter 9
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A statement as following will turn on both the transmitter and the receiver:
outportb(BASE + 7, 3);
3. AUTO
In the AUTO mode, the transmitter is enabled and the receiver is disabled
whenever outgoing data is available. Otherwise, the transmitter is disabled and
the receiver is enabled. No handshaking signals, such as RTS, are necessary.
Users can build a RS-485 network with just two wires. The RS-485 control is
completely transparent to users. This feature means RS-485 acts just like RS-232
in half duplex operation mode. Applications written for half-duplex RS-232 can
be used without modification.
Please refer to the sample program rs485.c in the \DOS\EXAMPLE\C directory for
more programming details.