[A83] Re: Interrupt troubles [83, Ion]
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[A83] Re: Interrupt troubles [83, Ion]
>From: "Kirk Meyer" <kirk.meyer@colorado.edu>
>
>I'm not exactly sure why that would return to the TIOS.
The outing to port 03h before the 'rst 38h' affects the way the interrupt
handler works. It probably lets it return to the TI-OS home screen.
>If the 83 port 3 is the same as the 86's, then that
>code first checks to see if the screen is updating (?! -
>this shouldn't matter on 83..) and then secondly does stuff
>with port 3 so that the ON key doesn't crash the calculator.
>However since you're calling the TIOS interrupt (presumably
>for the GetCSC support), it already does the second thing
>with port 3 for you. And I'm not sure whether the first thing
>with port 3 makes sense in light of the way the 83 updates
>its screen.
The only things that affect the lcd are port 04h, 10h, 11h (I think)
> > .exit_interrupt ;
> > in a,(3) ; check on interrupt status
> > rra ;
> > ld a,0 ;
> > adc a,9 ;
> > out (3),a ;
> > ld a,$0B ;
> > out (3),a ;
> > ;
> > exx ; Swap to shadow registers.
> > ex af,af ; So the TIOS swaps back to the
> > rst $38 ; normal ones... (the ones we saved
> > ex af,af ; with push/pops)
> > exx ;
> > pop bc ;
> > pop de ;
> > pop hl ;
> > pop af ;
> > ei ;
> > ret ;
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