[A83] Re: interrupt with shutdown
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[A83] Re: interrupt with shutdown
Yes, but you could put a DI at the start and then EI before the halt...
Michael Vincent
Detached Solutions - www.detacheds.com
Radical Software - www.radicalsoft.org
----- Original Message -----
From: "Tijl Coosemans" <tijl@ulyssis.org>
To: <assembly-83@lists.ticalc.org>
Sent: Sunday, December 09, 2001 9:49 AM
Subject: [A83] Re: interrupt with shutdown
>
> Hmm, I tried out the following two interrupt routines.
>
> ex af,af'
> bit 0,(iy+33)
> ret nz
> set 0,(iy+33)
> ex af,af'
> halt
> res 0,(iy+33)
> jp 0039h
>
> -------------------------------------
>
> ex af,af'
> bit 0,(iy+33)
> ret nz
> set 0,(iy+33)
> ex af,af'
> ei
> halt
> res 0,(iy+33)
> jp 0039h
>
> The first time the routine is called, it sets a bit and waits for an
> interrupt to happen (HALT). If that interrupt happens, it will return
> immediately (the bit is set), reset the bit and call the standard
> interrupt handler.
>
> The difference between the two routines is that the second one has an EI
> before the HALT and first one doesn't. Thus the second one always works
> and is merely meant to verify that the test works.
>
> The first routine however, will only work if interrupts are not disabled
> when an interrupt is accepted. If interrupts are disabled at the start of
> an interrupt, the HALT will cause the calculator to freeze.
>
> And that's what happened when I ran the first routine. The calc simply
> locked up. So I guess it's safe to remove the DI from the start of a
> custom interrupt routine.
>
> Tijl Coosemans
> http://tijl.studentenweb.org/
>
>
> > From: "Michael Vincent" <hookman@worldnet.att.net>
> >
> > A DI is good practice, because if your interrupt routine takes a long
> > time to run, another interrupt might be called before it's exited, and
then
> > it will start again...going into a loop of sorts.
> >
> > Michael Vincent
> > Detached Solutions - www.detacheds.com
> > Radical Software - www.radicalsoft.org
> >
>
> > > From: "Tijl Coosemans" <tijl@ulyssis.org>
> > >
> > >
> > > I just tested it out and a DI at the start of an interrupt routine is
> > > not necessary, at least not on the TI83-.
>
>
>
>
References: