199 lines
4.3 KiB
Plaintext
199 lines
4.3 KiB
Plaintext
processor 6502
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include "vcs.h"
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include "macro.h"
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include "xmacro.h"
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seg.u Variables
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org $80
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Score0 byte ; BCD score of player 0
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Score1 byte ; BCD score of player 1
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FontBuf ds 10 ; 2x5 array of playfield bytes
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Temp byte
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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seg Code
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org $f000
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Start
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CLEAN_START
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lda #$09
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sta Score0
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lda #$42
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sta Score1
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NextFrame
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VERTICAL_SYNC
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TIMER_SETUP 37
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lda Score0
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ldx #0
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jsr GetBCDBitmap
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lda Score1
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ldx #5
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jsr GetBCDBitmap
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TIMER_WAIT
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TIMER_SETUP 192
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; Draw 192 scanlines.
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; First, we'll draw the scoreboard.
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; Put the playfield into score mode (bit 2) which gives
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; two different colors for the left/right side of
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; the playfield (given by COLUP0 and COLUP1).
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lda #%00010010 ; score mode + 2 pixel ball
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sta CTRLPF
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lda #$48
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sta COLUP0 ; set color for left
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lda #$a8
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sta COLUP1 ; set color for right
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; Now we draw all four digits.
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ldy #0 ; Y will contain the frame Y coordinate
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ScanLoop1a
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sta WSYNC
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tya
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lsr ; divide Y by two for double-height lines
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tax ; -> X
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lda FontBuf+0,x
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sta PF1 ; set left score bitmap
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SLEEP 28
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lda FontBuf+5,x
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sta PF1 ; set right score bitmap
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iny
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cpy #10
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bcc ScanLoop1a
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; Clear the playfield
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lda #0
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sta WSYNC
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sta PF1
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; Turn playfield reflection off, since our brick field
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; will be drawn asymetrically (and turn score mode off)
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lda #%00010100 ; no reflection + ball priority + 2 pixel ball
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sta CTRLPF
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TIMER_WAIT
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TIMER_SETUP 30
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TIMER_WAIT
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jmp NextFrame
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; Fetches bitmap data for two digits of a
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; BCD-encoded number, storing it in addresses
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; FontBuf+x to FontBuf+4+x.
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GetBCDBitmap subroutine
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; First fetch the bytes for the 1st digit
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pha ; save original BCD number
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and #$0F ; mask out the least significant digit
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sta Temp
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asl
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asl
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adc Temp ; multiply by 5
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tay ; -> Y
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lda #5
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sta Temp ; count down from 5
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.loop1
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lda DigitsBitmap,y
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and #$0F ; mask out leftmost digit
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sta FontBuf,x ; store leftmost digit
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iny
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inx
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dec Temp
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bne .loop1
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; Now do the 2nd digit
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pla ; restore original BCD number
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lsr
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lsr
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lsr
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lsr ; shift right by 4 (in BCD, divide by 10)
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sta Temp
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asl
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asl
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adc Temp ; multiply by 5
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tay ; -> Y
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dex
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dex
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dex
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dex
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dex ; subtract 5 from X (reset to original)
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lda #5
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sta Temp ; count down from 5
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.loop2
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lda DigitsBitmap,y
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and #$F0 ; mask out leftmost digit
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ora FontBuf,x ; combine left and right digits
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sta FontBuf,x ; store combined digits
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iny
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inx
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dec Temp
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bne .loop2
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rts
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org $FF00
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; Bitmap pattern for digits
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DigitsBitmap
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.byte $0E ; | XXX |
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.byte $0A ; | X X |
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.byte $0A ; | X X |
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.byte $0A ; | X X |
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.byte $0E ; | XXX |
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.byte $22 ; | X X |
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.byte $22 ; | X X |
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.byte $22 ; | X X |
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.byte $22 ; | X X |
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.byte $22 ; | X X |
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.byte $EE ; |XXX XXX |
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.byte $22 ; | X X |
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.byte $EE ; |XXX XXX |
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.byte $88 ; |X X |
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.byte $EE ; |XXX XXX |
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.byte $EE ; |XXX XXX |
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.byte $22 ; | X X |
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.byte $66 ; | XX XX |
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.byte $22 ; | X X |
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.byte $EE ; |XXX XXX |
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.byte $AA ; |X X X X |
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.byte $AA ; |X X X X |
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.byte $EE ; |XXX XXX |
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.byte $22 ; | X X |
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.byte $22 ; | X X |
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.byte $EE ; |XXX XXX |
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.byte $88 ; |X X |
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.byte $EE ; |XXX XXX |
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.byte $22 ; | X X |
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.byte $EE ; |XXX XXX |
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.byte $EE ; |XXX XXX |
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.byte $88 ; |X X |
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.byte $EE ; |XXX XXX |
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.byte $AA ; |X X X X |
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.byte $EE ; |XXX XXX |
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.byte $EE ; |XXX XXX |
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.byte $22 ; | X X |
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.byte $22 ; | X X |
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.byte $22 ; | X X |
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.byte $22 ; | X X |
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.byte $EE ; |XXX XXX |
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.byte $AA ; |X X X X |
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.byte $EE ; |XXX XXX |
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.byte $AA ; |X X X X |
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.byte $EE ; |XXX XXX |
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.byte $EE ; |XXX XXX |
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.byte $AA ; |X X X X |
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.byte $EE ; |XXX XXX |
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.byte $22 ; | X X |
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.byte $EE ; |XXX XXX |
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; Epilogue
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org $fffc
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.word Start
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.word Start
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