; Kansasfest HackFest Entry ; Zero Page DRAW_PAGE = $EE CURRENT_OFFSET = $EF ; Soft Switches SET_GR = $C050 ; Enable graphics FULLGR = $C052 ; Full screen, no text PAGE0 = $C054 ; Page0 PAGE1 = $C055 ; Page1 LORES = $C056 ; Enable LORES graphics ; ROM routines TEXT = $FB36 ;; Set text mode HOME = $FC58 ;; Clear the text screen WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us ;=================== ; init screen jsr TEXT jsr HOME lda #0 sta DRAW_PAGE sta CURRENT_OFFSET ; Clear Page0 lda #$00 sta DRAW_PAGE jsr clear_gr ; draw border line lda #$55 ldy #38 jsr hline ; Clear Page1 lda #$4 sta DRAW_PAGE lda #$44 jsr clear_gr ; draw border line lda #$55 ldy #38 jsr hline ; temporarily draw HELLO ldy CURRENT_OFFSET ldx #0 data_loop2: lda words,Y sta $6d0,X lda words2,Y sta $750,X lda words3,Y sta $ad0,X lda words4,Y sta $b50,X iny inx cpx #40 bne data_loop2 ;===================================================== ; attempt vapor lock ; by reading the "floating bus" we can see most recently ; written value of the display ; we look for $55 (which is the grey line) ;===================================================== ; See: ; Have an Apple Split by Bob Bishop ; Softalk, October 1982 ; Challenges: each scan line scans 40 bytes. ; The blanking happens at the *beginning* ; So 65 bytes are scanned, starting at adress of the line - 25 ; the scan takes 8 cycles, look for 4 repeats of the value ; to avoid false positive found if the horiz blanking is mirroring ; the line (max 3 repeats in that case) vapor_lock_loop: ; first make sure we have all zeroes LDA #$00 zxloop: LDX #$04 wiloop: CMP $C051 BNE zxloop DEX BNE wiloop LDA #$55 ; now look for four all grey zloop: LDX #$04 qloop: CMP $C051 BNE zloop DEX BNE qloop ; found first line of low-res grey, need to kill time ; until we can enter at top of screen ; so we want roughly 10 lines * 4 = 40*65 = 2600+4550-65 ; +4550 - 65 (for the scanline we missed) = 7085 - 12 = 7073 ; GR part bit LORES ; 4 bit SET_GR ; 4 bit FULLGR ; 4 ; want 7073 ; Try X=26 Y=52 cycles=7073 lda #0 ; 2 lda #0 ; 2 ldy #52 ; 2 loopA: ldx #26 ; 2 loopB: dex ; 2 bne loopB ; 2nt/3 dey ; 2 bne loopA ; 2nt/3 jmp display_loop .align $100 ;================================================ ; Display Loop ;================================================ ; each scan line 65 cycles ; 1 cycle each byte (40cycles) + 25 for horizontal ; Total of 12480 cycles to draw screen ; Vertical blank = 4550 cycles (70 scan lines) ; Total of 17030 cycles to get back to where was ; We want to alternate between page1 and page2 every 65 cycles ; vblank = 4550 cycles to do scrolling ; 2 + 48*( (4+2+25*(2+3)) + (4+2+23*(2+3)+4+5)) + 9) ; 48*[(6+125)-1] + [(6+115+10)-1] display_loop: ldy #48 ; 2 outer_loop: bit PAGE0 ; 4 ldx #25 ; 130 cycles with PAGE0 ; 2 page0_loop: ; delay 126+bit dex ; 2 bne page0_loop ; 2/3 bit PAGE1 ; 4 ldx #23 ; 130 cycles with PAGE1 ; 2 page1_loop: ; delay 115+(7 loop)+4 (bit)+4(extra) dex ; 2 bne page1_loop ; 2/3 nop ; 2 lda DRAW_PAGE ; 3 dey ; 2 bne outer_loop ; 2/3 ; We have 4550 cycles in the vblank, use them wisely ; delay 4546 (+1 from loop falltrough, -2 for loadup, -3 for jmp) ; 4540 = x=9,y=89 ; kill 3 cycles lda DRAW_PAGE ; 3 lda DRAW_PAGE ; 3 ldy #89 ; 2 loop5: ldx #9 ; 2 loop6: dex ; 2 bne loop6 ; 2nt/3 dey ; 2 bne loop5 ; 2nt/3 jmp display_loop ; 3 ldy CURRENT_OFFSET ldx #0 data_loop: lda words,Y sta $6d0,X lda words2,Y sta $750,X lda words3,Y sta $ad0,X lda words4,Y sta $b50,X iny inx cpx #40 bne data_loop inc CURRENT_OFFSET lda #128 jsr WAIT jmp display_loop ;================================== ; HLINE ;================================== ; Color in A ; Y has which line hline: pha ; 3 ldx gr_offsets,y ; 4+ stx hline_loop+1 ; 4 lda gr_offsets+1,y ; 4+ clc ; 2 adc DRAW_PAGE ; 3 sta hline_loop+2 ; 4 pla ; 4 ldx #39 ; 2 hline_loop: sta $5d0,X ; 38 ; 5 dex ; 2 bpl hline_loop ; 2nt/3 rts ; 6 ;========================== ; Clear gr screen ;========================== ; Color in A clear_gr: ldy #46 clear_page_loop: jsr hline dey dey bpl clear_page_loop rts .align $100 words: ; H E L L O .byte $D1,$00,$D1,$00, $D1,$01,$00, $D1,$00,$00, $D1,$00,$00, $D0,$01,$D0,$00, $00, $00 ; K F E S T .byte $D1,$00,$D1,$00, $D1,$01,$00, $D1,$01,$00, $D1,$D1,$00, $01,$D1,$01,$00 ; 1 8 . . . .byte $00,$D1,$00, $D0,$01,$D0,$00, $00,$00,$00, $00,$00,$00, $00,$00,$00, $00,$00 .repeat 202 .byte $0 .endrep words2: .byte $24,$04,$24,$00, $24,$20,$00, $24,$20,$00, $24,$20,$00, $04,$20,$04,$00, $00,$00 .byte $24,$04,$20,$00, $24,$00,$00, $24,$20,$00, $20,$24,$00, $00,$24,$00,$00 .byte $00,$24,$00, $04,$20,$04,$00, $20,$20,$00, $20,$20,$00, $20,$20,$00, $00,$00 .repeat 202 .byte $0 .endrep words3: .byte $C9,$C0,$C9,$00, $C9,$C0,$00, $C9,$00,$00, $C9,$00,$00, $C9,$00,$C9,$00, $00,$00 .byte $C9,$C0,$09,$00, $C9,$C0,$00, $C9,$C0,$00, $C9,$C0,$00, $00,$C9,$00,$00 .byte $09,$C9,$00, $09,$C0,$09,$00, $00,$00,$00, $00,$00,$00, $00,$00,$00, $00,$00 .repeat 202 .byte $0 .endrep words4: .byte $06,$00,$06,$00, $06,$00,$00, $06,$00,$00, $06,$00,$00, $06,$00,$06,$00, $00,$00 .byte $06,$00,$06,$00, $06,$00,$00, $06,$00,$00, $00,$06,$00, $00,$06,$00,$00 .byte $00,$06,$00, $06,$00,$06,$00, $06,$06,$00, $06,$06,$00, $06,$06,$00, $00,$00 .repeat 202 .byte $0 .endrep gr_offsets: .word $400,$480,$500,$580,$600,$680,$700,$780 .word $428,$4a8,$528,$5a8,$628,$6a8,$728,$7a8 .word $450,$4d0,$550,$5d0,$650,$6d0,$750,$7d0