> In practice, I found out that the data
> pin of each
> register cannot be tied to a common data bus.

It can, but it probably won't have the effect you want.

> Is there a solution to do
> this ? (for 3 shift-registers, tie the Q7 data out pin to the
> same data bus D0 pin, which is also common to other circuits).

You seem to have found the solution. What is your question?

> Is it worth to have an address/data/command bus for a PIC
> project, which
> uses one latch, 3 shift-registers, one analog multiplexer and an ADC ?

Probably, if you need it for some purpose. But for the latch, 3 SR's,
mux and ADC you do not realy need it. And the normal way to operate a
PIC is not to create a data bus as found in a microprocessor system, but
to use the PIC pins to interace directly to your peripherals, using
tricks like SR's and serial ADC's to limit the number of pins used.

Wouter van Ooijen

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Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products

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