102 lines
2.5 KiB
ArmAsm
102 lines
2.5 KiB
ArmAsm
;=============================================
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; put_sprite
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;=============================================
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; Sprite to display in INH,INL
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; Location is XPOS,YPOS
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; Note, only works if YPOS is multiple of two?
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put_sprite:
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ldy #0 ; byte 0 is xsize ; 2
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lda (INL),Y ; 5
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sta CH ; xsize is in CH ; 3
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iny ; 2
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lda (INL),Y ; byte 1 is ysize ; 5
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sta CV ; ysize is in CV ; 3
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iny ; 2
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lda YPOS ; make a copy of ypos ; 3
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sta TEMPY ; as we modify it ; 3
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;===========
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; 28
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put_sprite_loop:
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sty TEMP ; save sprite pointer ; 3
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ldy TEMPY ; 3
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lda gr_offsets,Y ; lookup low-res memory address ; 5
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clc ; 2
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adc XPOS ; add in xpos ; 3
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sta OUTL ; store out low byte of addy ; 3
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lda gr_offsets+1,Y ; look up high byte ; 5
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adc DRAW_PAGE ; ; 3
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sta OUTH ; and store it out ; 3
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ldy TEMP ; restore sprite pointer ; 3
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; OUTH:OUTL now points at right place
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ldx CH ; load xsize into x ; 3
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;===========
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; 36
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put_sprite_pixel:
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lda (INL),Y ; get sprite colors ; 5
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iny ; increment sprite pointer ; 2
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sty TEMP ; save sprite pointer ; 3
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ldy #$0 ; 2
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; check if completely transparent
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; if so, skip
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cmp #$0 ; if all zero, transparent ; 2
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beq put_sprite_done_draw ; don't draw it ; 2nt/3
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; FIXME: use BIT? ;==============
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; 17
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sta COLOR ; save color for later ; 3
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; check if top pixel transparent
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and #$f0 ; check if top nibble zero ; 2
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bne put_sprite_bottom ; if not skip ahead ; 2nt/3
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lda #$f0 ; setup mask ; 2
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sta MASK ; 3
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bmi put_sprite_mask ; 2nt/3
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put_sprite_bottom:
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lda COLOR ; re-load color ; 3
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and #$0f ; check if bottom nibble zero ; 2
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bne put_sprite_all ; if not, skip ahead ; 2nt/3
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lda #$0f ; 2
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sta MASK ; setup mask ; 3
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put_sprite_mask:
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lda (OUTL),Y ; get color at output ; 5
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and MASK ; mask off unneeded part ; 3
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ora COLOR ; or the color in ; 3
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sta (OUTL),Y ; store it back ; 5
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jmp put_sprite_done_draw ; we are done ; 3
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put_sprite_all:
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lda COLOR ; load color ; 3
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sta (OUTL),Y ; and write it out ; 5
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put_sprite_done_draw:
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ldy TEMP ; restore sprite pointer ; 3
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inc OUTL ; increment output pointer ; 5
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dex ; decrement x counter ; 2
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bne put_sprite_pixel ; if not done, keep looping ; 2nt/3
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inc TEMPY ; each line has two y vars ; 5
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inc TEMPY ; 5
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dec CV ; decemenet total y count ; 5
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bne put_sprite_loop ; loop if not done ; 2nt/3
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rts ; return ; 6
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