You have to acknowlege the interrupt in software-EOI mode.
> I suspect the 'automatic end-of-interrupt mode' bit settings, as
> there's no way how to set it via a C function, AFAIK. Any ideas?
Since the EOI mode is global to all interrupts served by the MFP it is a
bad idea to change it.
OK, this is as far as I could get with my 'deassemblerize' mission:
Xbtimer( XB_TIMERA, 1<<3, 1, asm_timer_a ); // event count mode, count to '1'
Supexec( enableTimerASei ); // enable software end of interrupt
Jenabint( MFP_TIMERA );
and the handler:
_asm_timer_a:
movem.l d0-d1/a0-a1,-(sp)
jsr _timerA
movem.l (sp)+,d0-d1/a0-a1
rte
There are two problems with the handler: GCC by default doesn't save d0/d1/a0/a1 registers (nor the Xbtimer initialization does) and the handler must end with 'rte'. Any way out of this? (I deliberately ignore the fact that some MFP regs are irretrievably lost).