mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-11-04 05:05:13 +00:00
215 lines
3.9 KiB
ArmAsm
215 lines
3.9 KiB
ArmAsm
; Kansasfest HackFest Entry
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; Zero Page
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DRAW_PAGE = $EE
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CURRENT_OFFSET = $EF
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; Soft Switches
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SET_GR = $C050 ; Enable graphics
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FULLGR = $C052 ; Full screen, no text
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LORES = $C056 ; Enable LORES graphics
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; ROM routines
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TEXT = $FB36 ;; Set text mode
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HOME = $FC58 ;; Clear the text screen
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WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
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;===================
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; init screen
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jsr TEXT
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jsr HOME
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lda #0
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sta DRAW_PAGE
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sta CURRENT_OFFSET
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; Clear Page0
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lda #$00
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sta DRAW_PAGE
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jsr clear_gr
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; draw border line
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lda #$55
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ldy #38
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jsr hline
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; Clear Page1
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lda #$4
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sta DRAW_PAGE
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jsr clear_gr
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; draw border line
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lda #$55
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ldy #38
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jsr hline
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;=====================================================
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; attempt vapor lock
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; by reading the "floating bus" we can see most recently
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; written value of the display
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; we look for $55 (which is the grey line)
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;=====================================================
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; See:
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; Have an Apple Split by Bob Bishop
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; Softalk, October 1982
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; Challenges: each scan line scans 40 bytes.
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; The blanking happens at the *beginning*
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; So 65 bytes are scanned, starting at adress of the line - 25
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; the scan takes 8 cycles, look for 4 repeats of the value
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; to avoid false positive found if the horiz blanking is mirroring
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; the line (max 3 repeats in that case)
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vapor_lock_loop: ; first make sure we have all zeroes
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LDA #$00
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zxloop:
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LDX #$04
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wiloop:
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CMP $C051
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BNE zxloop
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DEX
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BNE wiloop
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LDA #$55 ; now look for four all grey
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zloop:
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LDX #$04
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qloop:
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CMP $C051
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BNE zloop
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DEX
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BNE qloop
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; found first line of low-res grey, need to kill time
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; until we can enter at top of screen
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; so we want roughly 5200+4550 - 65 (for the scanline we missed)
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; GR part
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bit LORES
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bit SET_GR
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bit FULLGR
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; want 9685
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; Try X=34 Y=55 cycles=9681
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lda #0 ; 2
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lda #0 ; 2
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ldy #55 ; 2
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loopA:
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ldx #34 ; 2
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loopB:
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dex ; 2
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bne loopB ; 2nt/3
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dey ; 2
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bne loopA ; 2nt/3
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jmp display_loop
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.align $100
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display_loop:
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ldy CURRENT_OFFSET
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ldx #0
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data_loop:
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lda words,Y
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sta $6d0,X
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lda words2,Y
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sta $750,X
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lda words3,Y
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sta $ad0,X
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lda words4,Y
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sta $b50,X
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iny
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inx
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cpx #40
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bne data_loop
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inc CURRENT_OFFSET
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lda #128
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jsr WAIT
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jmp display_loop
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;==================================
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; HLINE
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;==================================
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; Color in A
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; Y has which line
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hline:
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pha ; 3
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ldx gr_offsets,y ; 4+
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stx hline_loop+1 ; 4
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lda gr_offsets+1,y ; 4+
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clc ; 2
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adc DRAW_PAGE ; 3
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sta hline_loop+2 ; 4
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pla ; 4
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ldx #39 ; 2
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hline_loop:
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sta $5d0,X ; 38 ; 5
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dex ; 2
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bpl hline_loop ; 2nt/3
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rts ; 6
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;==========================
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; Clear gr screen
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;==========================
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; Color in A
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clear_gr:
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ldy #46
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clear_page_loop:
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jsr hline
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dey
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dey
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bpl clear_page_loop
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rts
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.align $100
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words:
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; H E L L O
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.byte $D1,$00,$D1,$00, $D1,$01,$00, $D1,$00,$00, $D1,$00,$00, $D0,$01,$D0,$00
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.repeat 239
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.byte $0
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.endrep
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words2:
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.byte $24,$04,$24,$00, $24,$20,$00, $24,$20,$00, $24,$20,$00, $04,$20,$04,$00
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.repeat 239
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.byte $0
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.endrep
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words3:
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.byte $C9,$C0,$C9,$00, $C9,$C0,$00, $C9,$00,$00, $C9,$00,$00, $C9,$00,$C0,$00
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.repeat 239
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.byte $0
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.endrep
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words4:
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.byte $06,$00,$06,$00, $06,$00,$00, $06,$00,$00, $06,$00,$00, $06,$00,$06,$00
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.repeat 239
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.byte $0
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.endrep
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gr_offsets:
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.word $400,$480,$500,$580,$600,$680,$700,$780
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.word $428,$4a8,$528,$5a8,$628,$6a8,$728,$7a8
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.word $450,$4d0,$550,$5d0,$650,$6d0,$750,$7d0
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