Olin Lathrop wrote:
>> I was using a 16F628 so everyting was on one code page.  ISR was
>> saving W, STATUS, FSR and PCLATH for good measure.  Is there
>> anything else that could potentially get me?
>
> Any other state that is shared between the interrupt and foreground
> code.

I take that as a no then, in the context of SFR's.

>> Without the ISR running, the foreground code wouldn't do anything but
>> loop, as it was waiting for the ISR to fill in a RAM location.  And
>> since the ISR was hit repeatedly so quickly by an external
>> interrupt, it would have been impossible to simulate with what I
>> have available.
>
> The simulator allows you to define how an external pin is wiggled over
> time in a file.  This might be useable to simulate your external
> interrupt.

I'll look into that.

>> I
>> even thought that since I had two interrupt sources, that maybe
>> somehow I was receiving another while the first was being serviced,
>> but that can't happen unless I reenable GIE, right?
>
> Right.
>
>> It would then print it to an LCD, and then
>> clear the RAM location, and go back into the tight loop.
>
> Was it possible to lose an interrupt by not clearing the RAM location
> fast enough?

AFAIK, no.  If another pulse stream came in while I was writing to the
LCD (which happens with the Sony type protocol of sending three bursts
of the same data in rapid succession), it would simply overlay the RAM
location once the entire burst was processed.  The timer interrupt was
there to tell me that no data had arrived for a while, and for me to
re-init my capture field and bits received counter.  Give me some time,
and I will try to duplicate the issue as you've really got me thinking
about this again.

I'm highly inclined to believe that I missed something obscure, as I
know better than to blame a CPU for odd behavior, no matter how odd.
It's just that with knowledge of the prior GIE issue and some of the
other documented issues, I was a tad more inclined to chalk it up to
some obscure problem with the CPU and int handling when using the
capture module and to let it slide.  Again, this is not my normal
practice.  I'm a bit to obsessive/compulsive to brush things like that
off.  ;-)

michael brown

"In the land of the blind, he who has one eye is king"

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