IRQ / VBL / trackloader

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heaven6502
Vic 20 Drifter
Posts: 27
Joined: Sat Jan 26, 2013 3:30 pm

IRQ / VBL / trackloader

Post by heaven6502 »

i am using a trackloader and need to switch IRQs for music playback...

sorry to ask dumb questions...

am I right that on the VIC a VBL is not triggered as IRQ/NMI? So everything is timer based?

when using stable rasterline routines (which use the 2 double timer) and I exit that part to load the next... how do I setup back the "standard" values and bits to run properly the IRQ for music while loading? talking about $0314/$0315...

I do

wait for rasterline #154
SEI
LDA #<22150
STA $9125
lda #>22150
STA $9126
lda #<music_IRQ
sta $0314
lda #>music_IRQ
sta $0315
cli

and what is the key to $0318/$0319 NMI? how is that handled properly? would be make sense to use NMI for music?

it's kind of confusing
groepaz
Vic 20 Scientist
Posts: 1180
Joined: Wed Aug 25, 2010 5:30 pm

Re: IRQ / VBL / trackloader

Post by groepaz »

what loader is it that you are using? generally for a demo type of thing, you need a "irq loader" which will work even if an irq is running (and then you just do it, you dont have to switch to original irq when running or whatever). on the other hand when using a "normal" loader, you cant play music while loading, as the loader itself would disable/enable the irq in undefined periods.
I'm just a Software Guy who has no Idea how the Hardware works. Don't listen to me.
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