Laurens Holst wrote:
>
> > This still doesn't answer the question whether interrupt cancelling
> is
> > possible.
> >
> > Scenario:
> > 1. DI
> > 2. enable interrupts at VDP level
> > 3. wait for some time, long enough for an interrupt to occur
> > 4. disable interrupts at VDP level
> > 5. EI
> > 6. test: does an interrupt occur?
>
> The interrupt does not occur.
> The VDP simply copies the value of the FH bit to the interrupt-pin of
> the
> slot.
> This pin remains set (and thus generating an interrupt, unless they
> are
> disabled using DI) until the corresponding statusregister is read.
>
> Since both are different statusregisters, they can overlap eachother.
>
> ~Grauw
>
Hello,
Just working my way trough all the mail I got during my vacation.
Interesting to know and never told in this entire discussion is the
following trick (One I used a lot in the beginning)
To reset a interrupt from a horizontal line interrupt (reg #19), I used
to set the interupt enable bit to zero and then back on again. Turning
the bit off also dropped the interrupt.
This was better because I could now make the interupt line drop in
lesser time, I just had two write twice to a register. With the official
read methode I had to write a register, wait, read a status register and
then put #15 back to zero (as assumed by the standard interrupt handler)
David Heremans
--
"One difference between SuSE and Red Hat is that the
former operates in a country where people don't sue
each other over coffee being too hot."
Linus Torvalds
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