> The problem is that when I attach the receiver for the synchronous data,
the
> stream begins to transmit incessantly.  It is unstable up to roughly 5.1V.
> Therefore, I'm led to wonder if the voltage applied affects the USART
> at all.  The peripheral that attaches to the PIC USART draws
> almost 500mA *from the power rails*.  I have tried attaching it to a
> seperate power supply, and I get the same result, but if I increase the
> voltage to the PIC slightly, it seems to stabilize a little, however, the
> USART seems to affect the bitbanged interface, and is causing it to abort
> transmissions part way through.

Are there large glitches on the line perhaps causing the protection diodes
to kick in?  Who is driving the data and clock lines when?  It sounds like
there is some kind of collision.  What do you mean by "unstable up to
roughly 5.1V"?


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