mirror of
https://github.com/sehugg/8bitworkshop.git
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137 lines
3.5 KiB
Plaintext
137 lines
3.5 KiB
Plaintext
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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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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;
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; This example demonstrates 48-pixel sprites.
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; We'll use a technique similar to the Asynchronous Playfields
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; trick -- reprogramming the TIA registers on-the-fly, writing
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; to each register multiple times during the scanline. If we
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; time our writes carefully, we'll be able to draw six unique
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; sprites per scanline, for example to draw a six-digit
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; scoreboard, or one large 48-pixel sprite.
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;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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seg.u Variables
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org $80
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Temp byte
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LoopCount byte
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THREE_COPIES equ %011
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seg Code
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org $f000
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Start
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CLEAN_START
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NextFrame
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VERTICAL_SYNC
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TIMER_SETUP 37
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lda #64
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sta LoopCount ; scanline counter
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lda #$ff
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sta COLUBK ; background color
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lda #$22
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sta COLUP0 ; show how players alternate
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lda #$12
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sta COLUP1 ; by having different colors
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lda #THREE_COPIES
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sta NUSIZ0
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sta NUSIZ1 ; both players have 3 copies
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sta WSYNC
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SLEEP 20
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sta RESP0 ; position 1st player
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sta RESP1 ; ...and 2nd player
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lda #$10
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sta HMP1 ; 1 pixel to the left
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sta WSYNC
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sta HMOVE ; apply HMOVE
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sta HMCLR
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lda #1
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sta VDELP0 ; we need the VDEL registers
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sta VDELP1 ; so we can do our 4-store trick
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TIMER_WAIT
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TIMER_SETUP 192
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SLEEP 40 ; start near end of scanline
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BigLoop
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ldy LoopCount ; counts backwards
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lda Bitmap0,y ; load B0 (1st sprite byte)
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sta GRP0 ; B0 -> [GRP0]
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lda Bitmap1,y ; load B1 -> A
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sta GRP1 ; B1 -> [GRP1], B0 -> GRP0
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sta WSYNC ; sync to next scanline
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lda Bitmap2,y ; load B2 -> A
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sta GRP0 ; B2 -> [GRP0], B1 -> GRP1
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lda Bitmap5,y ; load B5 -> A
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sta Temp ; B5 -> temp
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ldx Bitmap4,y ; load B4 -> X
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lda Bitmap3,y ; load B3 -> A
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ldy Temp ; load B5 -> Y
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sta GRP1 ; B3 -> [GRP1]; B2 -> GRP0
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stx GRP0 ; B4 -> [GRP0]; B3 -> GRP1
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sty GRP1 ; B5 -> [GRP1]; B4 -> GRP0
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sta GRP0 ; ?? -> [GRP0]; B5 -> GRP1
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dec LoopCount ; go to next line
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bpl BigLoop ; repeat until < 0
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TIMER_WAIT
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TIMER_SETUP 29
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TIMER_WAIT
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jmp NextFrame
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; Bitmap data, six columns
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align $100 ; ensure we start on a page boundary
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Bitmap0
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hex 00
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hex 00000000000000000000000000000000
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hex 00000000000000000000000000000001
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hex 01010205040402040404040404040404
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hex 040404060203000107df7f1f0f000000
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Bitmap1
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hex 00
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hex 0000073f1f0303000000000000010704
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hex 0808101010101412120a0a1e75c38000
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hex 0000076260e0e0e0c0c0e0e0c0c00000
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hex 00000000408170feffffffffc7030000
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Bitmap2
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hex 00
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hex 007ffffcf0e0c0404040404020bb7608
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hex 000402020809094f494949fa07010000
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hex 00000000006070f0f0f0c0e0e0e0e0e0
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hex 400000000010a06010e0e0f1ffff7f00
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Bitmap3
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hex 00
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hex 3effff07010000000000302159878184
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hex 848efeffffff9f0f0e9c7c0402c12010
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hex 08040207050000000002020104070f0f
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hex 0f070703030707070f1f7efcf8f0c000
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Bitmap4
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hex 00
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hex 00f0f0fffff0404040404080641e02c3
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hex 4242c3e2e2f4fcfc787838787cfa3131
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hex 6102021cf840c04042a022c14080c4c3
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hex c0c0c0c0808090900010180c04243800
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Bitmap5
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hex 00
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hex 000000fcfefc1c0c040402020202040c
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hex f800e01804040402020101010111e192
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hex dc700000000000000000000080808000
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hex 00000000000000000000000000000000
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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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