> Thanks for the response Lyle, Mike. In your opinion will a 'correctly'
> calibrated 12F675 communicate serially alright? Surely a 4MHz
> clock driven device is capable of that sort of timing?

When the other side uses a crystal: almost certainly yes. But IMHO not
certain enough for a commercial product.

When the other side is another F675 with internal osc: I guess yes, but
I would no even base a hobby project on it.

Note that there is more than just the clock accuracy that affect asynch
communication:
- a UART generally samples at a fixed (not synchronised!) rate (an
external interrupt based UART - not a timer interrupt based one - could
cancel this problem)
- the electronics will contribute some timing errors

Wouter van Ooijen

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