Change main file (forgot in previous commit.)
This commit is contained in:
Colin McMillen
parent
6fc775a411
commit
476495574f
112
pewpew.asm
112
pewpew.asm
@ -3,32 +3,6 @@
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.INCLUDE "registers.asm"
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; The JSR and RTS instructions add a total of 12 cycles of overhead. For
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; short, commonly-used functions, it makes sense to declare them as macros,
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; which get inlined by the assembler at the point of use. This saves on
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; CPU cycles, at the cost of code size.
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.MACRO ConvertXCoordinate
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; Data in: world x-coordinate, in A register.
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; Data out: SNES scroll data, in C (the 16-bit A register).
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rep #%00100000 ; 16-bit A
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eor #$FFFF ; Flip bits
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ina
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sep #%00100000 ; 8-bit A
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.ENDM
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.MACRO ConvertYCoordinate
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; Data in: world y-coordinate, in A register.
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; Data out: SNES scroll data, in C (the 16-bit A register).
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rep #%00100000 ; 16-bit A
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eor #$FFFF ; Flip bits
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sep #%00100000 ; 8-bit A
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.ENDM
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.BANK 0 SLOT 0
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.ORG 0
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@ -54,16 +28,16 @@ Start:
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jsr LoadPaletteAndTileData
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jsr InitializeSpriteTables
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; Set screen mode: 16x16 tiles for backgrounds, mode 0.
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lda #%11110000
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; Set screen mode: 16x16 tiles for backgrounds, mode 1.
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lda #%11000001
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sta SCREENMODE
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; Set sprite size to 16x16 (small) and 32x32 (large).
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lda #%01100000
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sta OAMSIZE
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; Main screen: enable sprites & BG2.
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lda #%00010010
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; Main screen: enable sprites & BG3.
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lda #%00010100
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sta MSENABLE
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; Turn on the screen.
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@ -88,7 +62,7 @@ Start:
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jsr FillScratch
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; Start the background color as a dark blue.
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lda #4
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lda #8
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sta $24
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; Player's initial starting location.
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@ -140,9 +114,11 @@ LoadPaletteAndTileData:
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cpx #32 ; 32 bytes of palette data.
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bne -
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; Now, BG2 palette data:
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; Now, BG3 palette data.
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; Palette entries for BG3 start at 0.
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; TODO(mcmillen): BG2 started at 32, but maybe that's only in mode 0?
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ldx #0
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lda #32 ; Palette entries for BG2 start at 32.
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lda #0
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sta CGADDR
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-
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lda.l TilePalette, X
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@ -163,7 +139,7 @@ LoadPaletteAndTileData:
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sta DMA0SRCBANK
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; DMA 0 transfer size.
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; See the helpful comment in sprites.asm to find the size of the tile data.
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ldx #576
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ldx #640
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stx DMA0SIZE
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; DMA 0 control register.
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; Transfer type 001 = 2 addresses, LH.
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@ -200,19 +176,19 @@ LoadPaletteAndTileData:
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lda #%00000001
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sta DMAENABLE
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; Tell the system that the BG2 tilemap starts at $4000.
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; Tell the system that the BG3 tilemap starts at $4000.
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lda #%00100000
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sta BG2TILEMAP
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; ... and that the background tile data for BG1 & BG2 starts at $2000.
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lda #%00010001
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sta BG12NBA
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sta BG3TILEMAP
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; ... and that the background tile data for BG3 starts at $2000.
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lda #%00000001
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sta BG34NBA
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; Set up the BG2 tilemap.
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; Set up the BG3 tilemap.
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; VRAM write mode: increments the address every time we write a word.
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lda #%10000000
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sta VMAIN
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; Set word address for accessing VRAM.
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ldx #$2000 ; BG 2 tilemap starts here. (Byte address $4000.)
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ldx #$2000 ; BG 3 tilemap starts here. (Byte address $4000.)
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stx VMADDR
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; Now write entries into the tile map.
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; We have only a couple tiles, but we set the invert horizontal/vertical
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@ -221,30 +197,51 @@ LoadPaletteAndTileData:
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; looking different.
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ldy #0
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-
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ldx #$0000
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stx VMDATA
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iny
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ldx #$0000
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stx VMDATA
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iny
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ldx #$0000
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stx VMDATA
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iny
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ldx #$0000
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stx VMDATA
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iny
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ldx #$0002
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stx VMDATA
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iny
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ldx #$0004
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stx VMDATA
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iny
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ldx #$4002
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stx VMDATA
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iny
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ldx #$8002
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ldx #$0000
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stx VMDATA
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iny
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ldx #$8004
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stx VMDATA
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iny
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ldx #$A002
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ldx #$0000
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stx VMDATA
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iny
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ldx #$0000
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stx VMDATA
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iny
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ldx #$0000
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stx VMDATA
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iny
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ldx #$4002
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stx VMDATA
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iny
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ldx #$0000
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stx VMDATA
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iny
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ldx #$0000
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stx VMDATA
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iny
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ldx #$A004
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stx VMDATA
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iny
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; The tile map is 32x32 (1024 entries).
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; This is the next multiple of 7 above that.
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cpy #1029
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; This is the next multiple of 14 above that.
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cpy #(74 * 14)
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bne -
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rts
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@ -489,6 +486,11 @@ UpdateGraphics:
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sta $0100
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lda $0021
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sta $0101
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; Choose which sprite based on frame count.
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lda $14
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and #%00000100
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lsr
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sta $0102
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; Set priority bits so that the sprite is drawn in front.
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lda #%00110000
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sta $0103
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@ -500,15 +502,15 @@ UpdateGraphics:
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; Make the background scroll. Horizontal over time; vertical depending on
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; player's y-coordinate.
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lda $14
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sta BG2HOFS
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sta BG3HOFS
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lda $15
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sta BG2HOFS
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sta BG3HOFS
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lda $21
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.rept 3
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lsr
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.endr
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sta BG2VOFS
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stz BG2VOFS
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sta BG3VOFS
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stz BG3VOFS
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rts
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