How to set serial port in semiduplex mode.

I have a serial card with rs485 and this port connect with a terminal
…Referring to some book ,I know rs485 work in
semiduplex mode.So I define the terminal work in semiduplex mode(refer the
terminal self intro).But I can only use devc-ser8250 to drive the rs485.How
to define the port to make it work in semiduplex mode?
My system is in qnx6.1.0.

I assume semiduplex is simplex… or half-duplex?!?

Often the hardware dictates if an RS-485 port is able to operate
in this mode or not. If the TX and RX control is integral to
the enable function in the hardware driver then you may only
have half-duplex operation available. On the other hand, sometimes
the TX enable is separate from RX enable and you can leave the RX
line on while TX, often used to listen for collisions.

Either case, the enable lines are typically run by the RTS signal
on a standard serial port and is controlled by the serial driver.
You may need to modify the serial driver (as we have done) to
accommodate this type of flow control.


zhz_zhang wrote:

I have a serial card with rs485 and this port connect with a terminal
.Referring to some book ,I know rs485 work in
semiduplex mode.So I define the terminal work in semiduplex mode(refer the
terminal self intro).But I can only use devc-ser8250 to drive the rs485.How
to define the port to make it work in semiduplex mode?
My system is in qnx6.1.0.