Opps, had to send this again because I didn't pay attention to the reply address.

Thanks Mike and Bob Ammerman for the thoughts.  For now I'll use the USART with an
open collector (as Alan suggested) or try the diode (as Harold suggested).  I've
always enjoyed  the journey more more so that the destination.  So trying different
methods is enlightening and fun.  I've ordered the parts, will start the program
development in a day or so.  With all the good comments and suggestions, I have
several alternatives if my present path doesn't work out.

Thanks again to all who responded.  What a great list.

Happy Trails........ Larry



Mike Singer wrote:

> Larry McKibben wrote:
>
> >  I'm not sure I want to add the complicity of RS485.
> > .
> > .
> > .
> > Reconsidering, I will abandon the USART.
>
>    Hello, Larry.
>
>    Why not to use the idea of Microchip ICSP interface in this context.
> Plus for more reliability I'd recommend star topology instead of bus.
> Plus for the same reason I'd recommend a sort of MAX232 stuff as
> bus drives. (I bought ICL232CPE for less then 1$)
>    What do I mean. PIC16F8XX has a lot of I/O pins. Set two lines
> (DataIn and DataOut) among central chip and each peripheral chip.
> Add two common lines (Reset and Syncro) from central to periferal.
> You'll get a fully static system with easy programming and debugging.
>    The idea is quite clear. After "Reset" you send commands in, say, 4 bits,
> synchronizing each bit by "Syncro" front. Then you send and receive data
> simultaneously going on with the synchronization.
>
>    Good luck.
>    Mike.
>
> PS: Microchip ICSP has DataIn and DataOut in one line. The above
>        idea looks more like an Atmel's SP.
>
> ----------------------------------------------------------------------------
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>
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Happy Trails....  Larry

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