Re: [avr-gcc-list] custom signal prologue

[Jim Brain]

Ben Mann wrote:

> Hi all,
>
> Is there any way to customise the prologue of an interrupt handler?
>  
I had the same issue.  I'm interested in responses you receive, but here
is what I did:

#ifdef JOY_ASM_INT
void SIG_OUTPUT_COMPARE1A (void) __attribute__ ((interrupt))
__attribute__ ((naked));    \
void SIG_OUTPUT_COMPARE1A (void) {
asm volatile ("push r24" ::);
asm volatile ("push __tmp_reg__" ::);
#else
INTERRUPT(SIG_OUTPUT_COMPARE1A) {
#endif
 // bring output high
 JOY_POT_PORT|=(1<<JOY_POT_PIN_X);
 // turn off IRQ
 TIMSK&=(unsigned char)~(1<<OCIE1A);
  sei();
 if((TIFR & (1<<OCF1B)) != 0) {
   JOY_POT_PORT|=(1<<JOY_POT_PIN_Y);
 }
#ifdef JOY_ASM_INT
asm volatile ("pop __tmp_reg__" ::);
asm volatile ("pop r24" ::);
asm volatile ("reti" ::);
#endif
}

I compile with JOY_ASM_INT undefined, and see what registers the routine
requires.  I then tweak the ASM and recompile with JOY_ASM_INT defined.

I'm not wild about my solution, but I absolutely had to remove all the
extraneous pushes and pops, or the code was worthless.

Jim



--
Jim Brain, Brain Innovations
address@hidden                                http://www.jbrain.com
Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times!