Hi Martin,

>I have been advised by a local contractor to use the MC14094 shift =
>register for the output multiplexer as I need to latch the values on the =
>port.  He also advised the 74HC597A as an input multiplexer.  The idea =

How about using 74HC589s for the input multiplexor.  The 74HC589's serial
output can be tri-stated.  The 74HC165 is also a parallel to serial shift
register that can be used for the inputs.

For the outputs, the 74HC164 is a serial to parallel shift register.
A better device is the 74HC595 (serial to parallel shift register with
latched 3-state outputs).

I'm in the similar situation where I need more I/O pins than the PIC
I am using (16F84) can supply.  I'm using 74HC589s to multiplex the inputs
and 74HC595s to multiplex the outputs.

I'm a newbie to PICs so I'm still playing around with this when I can get
a chance.

I had posted a similar note on the PICLIST a short while ago and
Paul B. Webster sent me several emails regarding possible solutions.
I can forward the emails to you if you want.  Let me know.

Regards,

-Randie
                                    ________
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