147 lines
1.6 KiB
ArmAsm
147 lines
1.6 KiB
ArmAsm
;div7_table = $9C00
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;mod7_table = $9D00
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;hposn_high = $9E00
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;hposn_low = $9F00
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;=====================
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; make /7 %7 tables
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;=====================
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; HGR_PAGE should be $20/$40 to select if default for hposn
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; is page1 or page2
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hgr_make_tables:
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ldy #0
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lda #0
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ldx #0
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div7_loop:
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sta div7_table,Y
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inx
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cpx #7
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bne div7_not7
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clc
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adc #1
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ldx #0
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div7_not7:
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iny
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bne div7_loop
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ldy #0
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lda #0
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mod7_loop:
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sta mod7_table,Y
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clc
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adc #1
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cmp #7
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bne mod7_not7
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lda #0
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mod7_not7:
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iny
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bne mod7_loop
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; Hposn table
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lda #0
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hposn_loop:
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ldy #0
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ldx #0
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pha
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jsr hposn ; (Y,X),(A)
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pla
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tax
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lda GBASL
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sta hposn_low,X
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lda GBASH
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sta hposn_high,X
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inx
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txa
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cmp #192
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bne hposn_loop
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rts
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; left masks
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; in memory on screen
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; x111 1111 1111111 start at 0
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; x111 1110 0111111 start at 1
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; x111 1100 0011111 start at 2
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; ...
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; x100 0000 0000001 start at 6
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left_masks:
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.byte $FF,$FE,$FC,$F8, $F0,$E0,$C0
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; right masks
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; in memory on screen
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; x000 0001 1000000 end at 0
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; x000 0011 1100000 end at 1
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; x000 0111 1110000 end at 2
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; ...
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; x011 1111 1111110 end at 5
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; x111 1111 1111111 end at 6
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right_masks:
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.byte $81,$83,$87, $8F,$9F,$BF,$FF
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; from the Apple II firmware
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hposn:
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; sta HGR_Y ; save Y and X positions
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; stx HGR_X
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; sty HGR_X+1
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pha ; Y pos on stack
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and #$C0 ; calc base addr for Y-pos
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sta GBASL
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lsr
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lsr
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ora GBASL
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sta GBASL
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pla
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sta GBASH
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asl
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asl
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asl
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rol GBASH
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asl
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rol GBASH
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asl
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ror GBASL
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lda GBASH
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and #$1F
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ora HGR_PAGE ; default is $40 in this game
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sta GBASH
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; txa
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; cpy #0
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; beq xpos_lessthan_256
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; ldy #35
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; adc #4
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;label_1:
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; iny
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;xpos_lessthan_256:
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; sbc #7
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; bcs label_1
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rts
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