Dear Néstor,
> your answer is very appreciated. I have refactored the code as you
> told, I put all the global variables in a header file, called
> "defs.h". I have also taken out all the calls to functions from the
> interrupt. Now, interrupt handler routine is a lot simpler. Just one
> thing: I haven't been able to disable the interrupt and save the stack
> with the code you gave me. Apparently, it should work, since I'm using
> a PIC 16F877, which seems to have 16 stack bytes. Am I missing
> something from your explanation?
What do you mean with you "haven't been able to disable interrupts and
save the stack" --- could you do either but not both, or none? How did
you find out that you did not succeed in performing the task?!?
Do you get compile time errors?
Run-time errors?
What precisely are the symptoms/error indications?
To make stack saving a bit more efficient, this afternoon I tried
(something like)
static void
Intr(void) __interrupt(0)
{
char int_status;
char int_stack[16];
__data char *src;
__data char *dst;
unsigned char u;
// disable interrupts (same as the macro)
int_status = INTCON & 0xC0;
INTCON &= 0x3F; // GIE = PIE = 0;
// save pseudo stack
src = (__data char *)0x70; // &STK00
dst = &int_stack[0];
for (u = 0; u < 16; u++)
{
*dst++ = *src++;
}
// handle timer interrupt
if (T0IF)
{
T0IF = 0; // re-arm for next interrupt
// --- more handler code ---
}
end:
// restore stack
src = &int_stack[0];
dst = (__data char *)0x70; // &STK00
for (u = 0; u < 16; u++)
{
*dst++ = *src++;
}
// restore/re-enable interrupts
INTCON |= int_status; // restore GIE and PIE
}
... and the .asm looks good (did not test on real hardware, though).
No meddling with GIE/PIE or T0IF/T0IE should be required in the
interrupt handler iff INTCON is masked and restored as shown.
Of course, you will have to enable GIE/PIE and T0IE at some point
in your program to enter the interrupt handler, but this seems to
be done in the menu handling code (if I recall correctly).
Rather puzzled,
Raphael
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