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// By ajhippel
// Crazy climber is one of the pcb's where the main cpu controlles the soundchip, which is the same like on the atari st..
// only the clock for the soundchip is a bit lower, but i transposed the song a bit higher...
// it's just a z80 player instead of the 68000 play-routine i used the old days...
// unfortunately there is only one interrupt (about 60hz) and no timer...with a timer i could add sid-voice and everything...
// the sine is indeed VERY simple...
// crazy climber has 32 scroll-registers for each column...wow i never had that on an atari st :)
// thats why the code is VERY short:
initialisation:
ld hl,sineoffsets ;pointer in the ram
ld b,32 ;32 columns
initsineoffsets:
ld a,b ;get b (32-1) as startdely
dec a ;make it 31-0)
ld (hl),a ;store delay
inc hl ;next column
djnz initsineoffsets
// and this is the sine-program:
dosine:
ld hl,sineoffsets ;points to 32 bytes free ram
ld de,#9800 ;pointer to the 32 scroll-registers
ld b,32 ;32 columns
dosinelp:
ld a,(hl) ;get offset in the sinetable
and a ;
jp m,sinewave ;when minus, then do the sine
dec a ;when positive, count down delay
ld (hl),a ;store it again
inc hl ;next column (ram)
inc de ;next column (scrollregister)
djnz dosinelp
ret
sinewave:
inc a ;increment offset
or #80 ;always make it negative (positive would be the initial delay)
ld (hl),a ;store offset
and #7f ;only 0-127
push hl ;store the pointer
ld h,HI sinetable ;get the high-byte of the sinetable-address
ld l,a ;offset = lowbyte of the address
ld a,(hl) ;get value from table
pop hl ;get the pointer again
inc hl ;increase the pointer
ld (de),a ;store value in the scroll-register
inc de ;increase pointer
djnz dosinelp ;next column
ret
// just make sure that the 128 bytes sinetable does not cross a 256 bytes border
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