On Wed, Mar 19, 2003 at 09:40:16AM +0000, Rowen Pereira wrote:
> I am doing a project in which i have to multiplex 
> the Rx and TX lines of the serial port on to one line.
> If i do this on an 'and' gate the single line remains 
> at a low (space) state.{Rx remains at mark if no data}
> I want to know what is "break" and  data is
> transmitted 
> after a long "Break".
> How is this data treated.

With RS232 a logic '0' is +12v and a logic '1' -12v (all line driver
chips are inverters).  So whatever you use has to be able to cope
with these voltages.

Line idle is constant 0 (ie +12v) so you might (at slowish speeds)
get away with a diode array and pullup resister.

> Is there any method you know that helps one to
> multiplex both TX and RX lines onto one line. 

The 'usual' way is to use RTS to request the line be switched, and CTS
to indicate that it has been switched.

	David

-- 
David Laight: david@l8s.co.uk