On Thu, 25 Mar 1999, Jeroen Smael wrote:
> Nestor Soriano wrote:
> > Hi people... problems again... this time, when changing stack. In a new
> > update of NestorAcentos I'm developing, I put the following piece of code
> > attached to the timer interrupt hook. The code is placed in a reserved zone
> > on page 3:
> >
> > ld (SAVESP),sp
> > ld sp,NEWSP+100
> > push all
> > .
> > . (changes slot and segment on page 2, do stuff and restores old status)
> > .
> > pop all
> > ld sp,(SAVESP)
> > jp old interrupt hook
> >
> > SAVESP: dw 0
> > NEWSP: ds 100
> >
> > Well, a program executing such code causes the system to crash when any
> > other program is executed. Someone knows where is the problem?
> >
> > Thanx!
>
> Hi Nestor,
>
> Perhaps a stupid remark, but do you call this routine or do you jump to
> it? If you call it, the JP at the end causes your problem. If you jump
> to this routine, I don't see anything wrong with it (somebody else?).
hmm.. it is just the other way around; if he CALLs it, it is ok because
the old_interrupt_hook RETurns.
Do you perform BDOS routines during your interrupt Nestor? And do you use
it in DOS1 or DOS2 environment?
Also stupid: don't forget to push/pop IX/IY and shadowregisters.
Greetz,
jon
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