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59 lines
1.1 KiB
ArmAsm
59 lines
1.1 KiB
ArmAsm
; Xdraw Wave
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; repeatedly draws an image from an Apple II shape table
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; this time we rotate a bit
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; we also go for a bit of sound
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; loads at $E7 which sets the HGR_SCALE zero-page value for free
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; zero page locations
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; ROM calls
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HGR2 = $F3D8
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HPOSN = $F411
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XDRAW0 = $F65D
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.zeropage
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.globalzp rot_smc
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xdraw_wave:
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jsr HGR2 ; Hi-res, full screen ; 3
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; Y=0, A=0 after this call
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; we load at $E7 which is HGR_SCALE, so HGR_SCALE gets
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; the value of the above JSR instruction ($20)
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; A and Y are 0 here.
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; X is left behind by the boot process?
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tax
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jsr HPOSN ; set screen position to X= (y,x) Y=(a)
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; saves X,Y,A to zero page
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; after Y= orig X/7
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; A and X are ??
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tiny_loop:
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; values for shape table
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; Y X
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; 00 E7 = neat
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; 00 EB = OK
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; 00 EF = good
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; F0 01 = cool, let's go with it
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; ldx #$01 ; point to bottom byte of shape address
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ldy #$f0 ; point to top byte of shape address
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; ROT in A
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; this will be 0 2nd time through loop, arbitrary otherwise
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lda #5 ; ROT=0
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jsr XDRAW0 ; XDRAW 1 AT X,Y
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; Both A and X are 0 at exit
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; Z flag set on exit
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; Y varies
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beq tiny_loop ; bra
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