pic microcontroller discussion list <> wrote:
> I have two rs232 connections and I would like to send/receive from
> both of them, *not* at the same time.  Can I connect the two of them
> to the same RX/TX line and somehow select comm1 and comm2 from the
> pic?

You can put each TTL level comms line into one input of an OR gate, with
the other input of each OR gate going to separate PIC pins.  Feed the two
outputs of the OR gates into an AND, the output of the AND goes into the
PIC USART pin.

If either of the control lines is low, that port's data will pass through
to the PIC.  (TTL level serial comms idles high)

That's the basic idea, you could reduce it to one control pin from the PIC
without much extra logic

Nigel
--
Nigel Orr, Design Engineer                 nigel@axoninstruments.co.uk
Axon Instruments Ltd., Wardes Road,Inverurie,Aberdeenshire,UK,AB51 3TT
               Tel:+44 1467 622332 Fax:+44 1467 625235
                   http://www.axoninstruments.co.uk

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