> >IE0 is to enable/disable interrupts from a lightpen/mouse connected to
the
> >v9938/58. However, in the MSX system the mouse is read through the PSG
and a
> >lightpen is most of the time not connected (you'll have to solder on your
> >VDP to do that... there is no connector for it).
>
> Oops I think I completelty messed the bit numbering in my previous post.
>
> My Portar doc says this lightpen/mouse thing is done by bit IE2 (that's
bit #5
> of register 1), whereas IE0 (bit #5 of register 0) is the vertical
retrace
> enable. Surely my docs are wrong then?
Err, probably not. I did it from memory.
Okay, to set things straight:
IE0: Enable line 212-interrupt
IE1: Enable interrupt when line specified in r#19 is reached (different from
IE0)
IE2: Enable Mouse/Lightpen interrupt
> >On MSX it is #FF by default. However, this is not specified in the MSX
> >system (in fact IM1 is the only official interrupt-mode, although IM2 can
be
> >used too) so it can actually have any value because of a distortion or
so...
> >All programs should fill the entire area from I*256 to (I+1)*256
(INCLUDING
> >the last byte!!!)...
>
> I know this method already (as a matter of fact it's the one I chose just
to
> make sure everything worked ok). I just wanted to know if I could assume
any
> defalut value.
Well as I stated if programming an emulator yes if programming an MSX app
no.
> >I wrote a very extended article about it in one of the most recent
> >XSW-Magazine issues... You should really take a look at that. But it's in
> >Dutch, though.
>
> Pity my Dutch's a bit too crusty these days :)
>
> Thanks Laurens
It's okay.
~Grauw
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