Dan Michaels wrote:
>
> Peter Vogel wrote:
> >I am trying to find out the relationship between the osc input and reading
> of data from an IO port. The 16F87X manual I have suggests 100nS hold time
> is required, which cannot be correct for the 20MHz part.
> >
> >Where can I find the timing diagrams for this?
> >
>
> Look around in the datasheets for something describing which
> specific operations are performed during each instruction
> quarter-cycle.
>


Try the 16C84 datasheet, page 23. The C84 datasheet was
the first flash chip and Mchip took a lot of effort
with its documantation. It has LOTS of data and
explanations that are NOT in the more recent datasheets.

I printed it out and I constantly see questions asked
on the list that are clearly covered in the C84 datasheet
but not in the F84 or F87x datasheets.

The input pins are read on the end of the first clock,
the pin writes happen at the end of the last clock.
Hence the read-modify-write problem.

The C84 datasheet also has very nice timing diagrams
for TIMER0 clocking (page 25), TIMER0 external
clocking (page 27) INT pin int timing (page 45)
and more. Well worth printing out 80 pages and
$1 for a folder to put it in.
:o)
-Roman

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