mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-06-08 15:29:41 +00:00
133 lines
1.9 KiB
ArmAsm
133 lines
1.9 KiB
ArmAsm
; wires -- Apple II Hires
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; D0+ used by HGR routines
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HGR_COLOR = $E4
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HGR_PAGE = $E6
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GBASL = $26
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GBASH = $27
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HGR_END2 = $FC
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HGR_END = $FD
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COUNT = $FE
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FRAME = $FF
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; soft-switches
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PAGE1 = $C054
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PAGE2 = $C055
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; ROM routines
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HGR2 = $F3D8 ; set hires page2 and clear $4000-$5fff
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HGR = $F3E2 ; set hires page1 and clear $2000-$3FFF
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WAIT = $FCA8 ; delay 1/2(26+27A+5A^2) us
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wires:
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jsr HGR
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jsr HGR2 ; clear screen PAGE2 A and Y 0 after
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reset_x:
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ldx #$0
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switch_pages:
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lda HGR_PAGE
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eor #$60
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sta HGR_PAGE
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cmp #$40
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bne switch_page2
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bit PAGE1
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jmp outer_loop
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switch_page2:
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bit PAGE2
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outer_loop:
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;=====================================
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; pulse loop horizontal
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;=====================================
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; write out pattern to horizontal line
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; due to memory layout by going $4000-$43FF only draw every 8th line
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lda #$00
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tay
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sta GBASL
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lda HGR_PAGE ; point GBASL to $4000
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sta GBASH
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clc
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adc #$4
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sta HGR_END
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adc #$1C
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sta HGR_END2
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horiz_loop:
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lda even_lookup,X
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sta (GBASL),Y
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iny
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lda odd_lookup,X
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sta (GBASL),Y
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iny
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bne noflo2
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inc GBASH
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noflo2:
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lda HGR_END
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cmp GBASH
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bne horiz_loop
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;========================================
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; vertical loop
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;========================================
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; A should already be $44 here
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; Y should be 0
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; X is position in pattern
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; to be honest I don't remember how this works
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vert_loop:
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txa
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clc
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adc #2 ; $44 + 2? = $46
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asl ; = $8E
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asl ; shift left? = $1C + carry
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adc HGR_PAGE ; what? = $5D
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sbc GBASH ; huh - $44 = $19
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cmp #8 ; WHAT IS GOING ON HERE?
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lda #$81
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bcs noeor
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ora #$02
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noeor:
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sta (GBASL),Y ; store it out
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inc GBASL ; skip two columns
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inc GBASL
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bne noflo
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inc GBASH
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noflo:
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lda HGR_END2
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cmp GBASH
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bne vert_loop
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inx ; wrap at 7
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cpx #7
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beq reset_x
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bne switch_pages ; bra
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even_lookup:
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.byte $D7,$DD,$F5, $D5,$D5,$D5,$D5
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odd_lookup:
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.byte $AA,$AA,$AA, $AB,$AE,$BA,$EA
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