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added FASTSCAN

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Charles Mangin 2018-08-15 16:13:25 -04:00 committed by GitHub
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DSK FASTSCAN
**************************************************
* To Do:
*
**************************************************
* Variables
**************************************************
CHAR EQU $FC ; char/pixel to plot
DELAY EQU $03
DIRECTION EQU $02
**************************************************
* Apple Standard Memory Locations
**************************************************
CLRLORES EQU $F832
LORES EQU $C050
TXTSET EQU $C051
MIXCLR EQU $C052
MIXSET EQU $C053
TXTPAGE1 EQU $C054
TXTPAGE2 EQU $C055
KEY EQU $C000
C80STOREOFF EQU $C000
C80STOREON EQU $C001
STROBE EQU $C010
SPEAKER EQU $C030
VBL EQU $C02E
RDVBLBAR EQU $C019 ;not VBL (VBL signal low
WAIT EQU $FCA8
RAMWRTAUX EQU $C005
RAMWRTMAIN EQU $C004
SETAN3 EQU $C05E ;Set annunciator-3 output to 0
SET80VID EQU $C00D ;enable 80-column display mode (WR-only)
HOME EQU $FC58 ; clear the text screen
CH EQU $24 ; cursor Horiz
CV EQU $25 ; cursor Vert
VTAB EQU $FC22 ; Sets the cursor vertical position (from CV)
COUT EQU $FDED ; Calls the output routine whose address is stored in CSW,
; normally COUTI
STROUT EQU $DB3A ;Y=String ptr high, A=String ptr low
ALTTEXT EQU $C055
ALTTEXTOFF EQU $C054
ROMINIT EQU $FB2F
ROMSETKBD EQU $FE89
ROMSETVID EQU $FE93
ALTCHAR EQU $C00F ; enables alternative character set - mousetext
BLINK EQU $F3
SPEED EQU $F1
**************************************************
* START - sets up various fiddly zero page bits
**************************************************
ORG $2000 ; PROGRAM DATA STARTS AT $2000
DRAWBOARD JSR HOME
JSR MESSAGE ; 8677 cycles.
LDA #$11
STA CHAR
STA DIRECTION
STA DELAY
LDA #$01
STA SPEED
JSR FILLSCREENFAST ; 6023 cycles.
* read the VBL
READVBL BIT RDVBLBAR ; 4
* if bit7 = 0, then VBL active
BMI READVBL ; 2 wait until refresh interval
* set TEXT during VBL
STA TXTSET ; 4
STA TXTPAGE1
* read the VBL again
READVBL2 BIT RDVBLBAR ; 4
* if bit7 = 1, then VBL active
BPL READVBL2 ; 2 loop while VBL is happening
* VBL is over
* do something while the screen draws a bit
* Screen draws in 12480 instructions
LDA DIRECTION ; incrementing or decrementing?
ROR ; bit 0 into Carry
BCC INCREMENT ; even = increment, odd = decrement
DECREMENT DEC DELAY ; scan line going up
STA TXTPAGE1 ; show page 1 ( message )
JMP XLOOP ; wait
INCREMENT INC DELAY ; scan line going down
XLOOP LDX DELAY
BEQ NOLOOP
CPX #$FF
BEQ NOLOOP
XLOOP2 NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
NOP ; 2
DEX ; 2
BNE XLOOP2 ; 2
* set GR at bottom of screen
NOLOOP STA LORES ; 4
STA TXTPAGE2
LDA DELAY
CMP #$C0
BCS GOFILL ; == C0 change directions
* loop until the next blank
GOLOOP JMP READVBL
GOFILL INC DIRECTION ; equal or greater than c0, change colors
LDA CHAR
CLC
ADC #$11
STA CHAR
JSR FILLSCREENFAST ; change colors when loop length is >C0
JMP READVBL
**************************************************
* writes message
**************************************************
HELLOWORLD ASC "Check out what I learned at Kansasfest!",00 ; set to ascii for message
MESSAGE
LDA #$0B
STA CV ; jump down
JSR VTAB
LDA #$00
STA CH
LDY #>HELLOWORLD
LDA #<HELLOWORLD
JSR STROUT ;Y=String ptr high, A=String ptr low
RTS
;/MESSAGE
**************************************************
* blanks the screen quickly.
* https://www.atarimagazines.com/compute/issue10/032_1_THE_APPLE_GAZETTE.php
**************************************************
; FOR EACH ROW/COLUMN
FILLSCREENFAST ; 6023 instructions
FLASH LDA CHAR ; Get selected color byte
LDY #$78 ; Prepare to fill 120 bytes
JSR FILL1 ; Fill four sets of 120 bytes each
LDY #$78 ; Prepare to fill 80 bytes
JSR FILL2 ; Fill four sets of 80 bytes each
RTS ; Done. Return.
FILL1 DEY
STA $800, Y
STA $880, Y
STA $900, Y
STA $980, Y
BNE FILL1
RTS
FILL2 DEY
STA $a00, Y
STA $a80, Y
STA $b00, Y
STA $b80, Y
BNE FILL2
RTS