Re: [cc65] C64, Interrupt and in need of an example

Please don't forget to acknowledge pending  irq's. Do the
irq-init immediately before the cli, else an irq could be
triggered while initializing screen memory or bitmaps
or music! This applies whether you use C or pure assembler!
In the _c_irq you have to backup the whole zp-segment, so that you
don't disturb the c-code outside the irq.

.IMPORT _c_irq

sei

lda #0
tax
tay
jsr init	; $1000

lda #>_c_irq
sta $0315
lda #<_c_irq
sta $0314
lda #$7f
sta $dc0d
bit $dc0d (<-never forget!)
lda #$01
sta $d01a
lda #$32
sta $d012
lda #$1b
sta $d011 (<-never forget!)

lsr $d019 (<-never forget!)

cli
rts

irq:
inc $d020
jsr play	; $1003
dec $d020
jmp $ea31

Greetz Monte Carlos

> On Donnerstag 28 Februar 2008, Markus Stehr wrote:
>   
>> Hi!
>>
>> Could someone please provide me with an usable example for an interrupt
>> for the C64? I have been reading the manual and asked Google for 2 hours
>> now and i am as clueless as i was 2 hours ago.
>>     
>
> sei
> lda #>irq
> sta $0315
> lda #<irq
> sta $0314
> lda #$7f
> sta $dc0d
> lda #$01
> sta $d01a
> lda #$32
> sta $d012
> lda #$1b
> sta $d011
>
> lda #0
> tax
> tay
> jsr init	; $1000
>
> cli
> rts
>
> irq:
> inc $d020
> jsr play	; $1003
> dec $d020
> jmp $ea31
>
> ... something like that :)
>
>   



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