Hi,

Bart Stofferis wrote:
>
> Hi there !!
>
> Name here is Bart, and i have got some problems with my LUTs (lookup
> tables) & PIC16C73A or 16C76.
>
> I have to implement 10 tables of 127 bytes and the problem is that when
> an interrupt occurs the
> program counter jumps somewhere in space ... lost in space ...
>
> I don't understand the program counter mechanism very well ...
>
> Can someone reserve some time to have a look at my experiments
>
> I have included 2 files, the main program file and the LUT-file
>
> Thanks a lot ... and enjoy !
>

While I didn4t look through the whole programm, I would suggest4,
to copy the interrupt service routine to each page. I think that
when processing the irq, just the actual PC is pushed onto the stack.
And because of the WIDTH of the PC only addresses within a page
are pushed, popped or jumped to.

Trying to explain it in a different way:

You may think of the Pic-rom as like to have e.g. some ROM chips with a
chipselect done by a external register.

the external register doesn4t know about irq4s so either a bankswitch to
the ISR in bank 0 has to be executed ( routine to do that has to be e.g.
in bank  1 at the same location as where the original routine is located
in bank 0 ) or just copy the ISR to each used bank. The later suggestion
prevents you from keeping track where your jump to ISR came from.

Kind regards,

        Stefan