Jon Hylands wrote:
>
> On Tue, 9 May 2000 14:38:25 -0400, you wrote:
>
> > Any suggestions on an easier to interface add-on chip or type of PIC?
>
> What I have done so I can use 16F84s in a master/slave serial bus is
> to dedicate the INT pin on each slave to be the signal line. The
> master pulls the line low for a few hundred microseconds (the time the
> line is pulled low needs to be slightly greater than the length of the
> longest interrupt on any slave).
>
> The slaves all go into the ISR for the INT line, and watch the signal
> line (polling). When it goes high, the master proceeds to clock out 8
> bits, which is the slave address to send to. The slaves are all
> syncronized, so they each receive the byte and compare it to their
> slave ID. If it is the same, they do whatever is approriate in
> communication with the master. If its not, they ignore everything else
> on the data line and exit the ISR, not to be bothered again until the
> signal line gets pulled low again. Only the master may pull the signal
> line.
>
> Very simple, very easy to do, very direct, and it works great. I
> wouldn't pass huge amounts of data over this bus in one transaction,
> since there is no clock pulse to do bit-synching with. But if all
> you're doing is sending simple commands and receiving status info, it
> works pretty well. The master can be connected to a MAX232 or whatever
> to talk to the PC/Palm device.
>
> Its certainly not a 100% efficient solution, but it is very simple to
> implement, which for me is much more important...
>
> Later,
> Jon

Jon,
Would it be possible to see your code for this? I was thinking of doing
something similar, but I was going to implement full I2C in the slaves.

Thanks
Josh Koffman
joshy@mb.sympatico.ca