Hi Ken,

you wrote:
> ...
> Every time someone criticized my engineering work, be it hardware,
software,
> or firmware, it has made me a much better designer.
I, too, have learned to appreciate constructive criticism; and, believe me -
I've had
my share! - but that's not what I've had my hackles raised about!

you wrote:
> Are you able to pump out some registers out the serial port for debugging
> purposes?
> Olin gave you a hint about a possible bad coding practice -- maybe FSR
> related?
> Is the ISR modifying the bank select register?

!!! I think I'm onto something!

Due to the sporadic nature of the "failure" [which was that B1_COUNT was
getting trashed], it appears that something asynchronous to the main
execution thread must be the culprit.  So, I went directly to the ISR with
my suspicions:  far as I can see, ISR is as correct as it can be... *IF*
execution was interrupted from Bank 0 !   The ISR saves 'W', 'STATUS', 'FSR'
etc. into temp variables that are defined in Bank 0.   Now, I've not written
code before that operates on Data Memory in Bank1...3.   Could it possibily
be that I need to 'shadow' my ISR Temp variables in each Bank?  As it turns
out, my "W_TEMP" variable is allocated at address 0x20 (bank 0).  What is
supposed to happen if, while I'm executing code that's referencing Bank 1, I
get an interrupt and attempt to save "w" in "W_TEMP" (0x20)?   I'm guessing
that this might be the source of 0xA0 being whacked?  Does this sound right
to you?
I did one experiment that seems to reinforce my conjecture: moved the data
structure definition to be based at address 0xA1... never see any execution
problems (after MANY retries!).
I've got to try one more experiment: to see if the value that "clobbers"
0xA0 was in fact the "W" value being saved by the ISR.
To quote "Arnold"... "I'll be back!"
Jim

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