This way I have a few bits too few. I am using a PIC16C84, which has a
total of 13 I/O bits. But if I use only 3 address-bits, and preset the
ttransceivers for either input or output this should worh (I hope)

Hans

Nicholas Irias wrote:
>
> One possible solution is to use tri-state 8-bit bus transceivers at
> each of the 4 destinations or sources.  You can use 4-bit magnitude
> comparators at each destination to compare a bus address to the
> destination address, and use the address==address to enable the
> transceiver.  This supports 16 addresses.
>
> This requires a bus with 8 data lines, 4 address lines, and one flow
> control line, to control the data direction of the selected transceiver.
>
> This method is definitely bulkier and less elegant than a 2 wire
> I2C bus, but your software winds up being incredibly simple, at
> least if each slave device is either always an input or always an
> output.  The software in a slave device is just reading or writing to
> its 8 pins, and can be oblivious to the outside world.  No need to
> perform some communication task every few uSecs.
>
> The relevant parts are DM74LS85 and DM74LS245.  Note that you
> will need to invert the A==B output from the magnitude comparator
> before feeding it into the transceiver.
>
> ----------
> > From: H.P. de Vries <H.P.d.Vries@stud.tue.nl>
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: MUX
> > Date: Friday, February 13, 1998 8:28 PM
> >
> > Does anyone know of a Bidirectional 32-8 multiplexer? (or 16-4, 4-1)
> >
> > I want to multiplex an 8-bit I/O port of a PIC to 4 sources/destinations
> > of/for the data. I hope somone understands this ....
> >
> > Hans