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PICList Thread
'[PIC]: 16F87x read port timing spec'
2001\02\21@221645 by Dan Michaels

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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.

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2001\02\22@005347 by Roman Black

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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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2001\02\22@090905 by severson

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>
> 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.
>

Is this data sheet still available?

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2001\02\22@094012 by severson

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> > > 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.
> > >
> >
> > Is this data sheet still available?
>
> Try this.
>
> http://www.thepicarchive.cwc.net/documents.htm
>
> David

Thanks, but this just points to the microchip site, and a page error.

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2001\02\23@041304 by Roman Black

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Rob Severson wrote:
>
> >
> > 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.
> >
>
> Is this data sheet still available?


It is on my computer! :o)
I can put it up for downloading if it's
not available from Microchip anymore.

Most of the nice diagrams and explanations
are available in the huge Mchip mid-range
reference manual. It's just nice having them
in the chip datasheet along with the C84 specific
stuff.

My Picstart came with a 16C84, so i obtained
the datasheet. When I started using 16F84 I
realised the datasheet for it was cut down.
I think Mchip assumes we all know all the
quirks by now, which is a shame for newbies.
Probably like most people I always use a
datasheet and never use the mid-range ref
manual.:o)
-Roman

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