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828362f3cb
dos33fsprogs/kfest2018/raster.s
Vince Weaver 828362f3cb kfest: starting at right point
2018-07-19 23:19:38 -04:00

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; 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
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