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Change main file (forgot in previous commit.)

main
Colin McMillen 9 years ago
parent
commit
476495574f
  1. 106
      pewpew.asm

106
pewpew.asm

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

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