Using Tile Studio, I created a small 32 tile x 32 tile background with a large '3' in the background made up of small '3' tiles as shown below.
I confirmed the shape of the hex data using the program HxD as shown below
The problem is, when changing the source file in the code to point to my background, the background is loaded 90 degrees clockwise. Instead of a 3 in the background, it's more like a W. The small red square at the top right of the screenshot should be the first piece of data loaded into $2007, and the data should be loaded in the direction of the arrow I believe.
I have a feeling it may be in the way that the nametable is loaded, but I can't seem to pinpoint why it would be loading the bottom left part of the binary file into $2000. Any thoughts?
The full code to scrolling5.nes is below
Code: Select all
.inesprg 1 ; 1x 16KB PRG code
.ineschr 1 ; 1x 8KB CHR data
.inesmap 0 ; mapper 0 = NROM, no bank swapping
.inesmir 1 ; VERT mirroring for HORIZ scrolling
;;;;;;;;;;;;;;;
;; DECLARE SOME VARIABLES HERE
.rsset $0000 ;;start variables at ram location 0
scroll .rs 1 ; horizontal scroll count
nametable .rs 1 ; which nametable to use, 0 or 1
columnLow .rs 1 ; low byte of new column address
columnHigh .rs 1 ; high byte of new column address
sourceLow .rs 1 ; source for column data
sourceHigh .rs 1
columnNumber .rs 1 ; which column of level data to draw
;;;;;;;;;;;;
.bank 0
.org $C000
RESET:
SEI ; disable IRQs
CLD ; disable decimal mode
LDX #$40
STX $4017 ; disable APU frame IRQ
LDX #$FF
TXS ; Set up stack
INX ; now X = 0
STX $2000 ; disable NMI
STX $2001 ; disable rendering
STX $4010 ; disable DMC IRQs
vblankwait1: ; First wait for vblank to make sure PPU is ready
BIT $2002
BPL vblankwait1
clrmem:
LDA #$00
STA $0000, x
STA $0100, x
STA $0300, x
STA $0400, x
STA $0500, x
STA $0600, x
STA $0700, x
LDA #$FE
STA $0200, x
INX
BNE clrmem
vblankwait2: ; Second wait for vblank, PPU is ready after this
BIT $2002
BPL vblankwait2
LoadPalettes:
LDA $2002 ; read PPU status to reset the high/low latch
LDA #$3F
STA $2006 ; write the high byte of $3F00 address
LDA #$00
STA $2006 ; write the low byte of $3F00 address
LDX #$00 ; start out at 0
LoadPalettesLoop:
LDA palette, x ; load data from address (palette + the value in x)
STA $2007 ; write to PPU
INX ; X = X + 1
CPX #$20 ; Compare X to hex $10, decimal 16 - copying 16 bytes = 4 sprites
BNE LoadPalettesLoop ; Branch to LoadPalettesLoop if compare was Not Equal to zero
; if compare was equal to 32, keep going down
LoadSprites:
LDX #$00 ; start at 0
LoadSpritesLoop:
LDA sprites, x ; load data from address (sprites + x)
STA $0200, x ; store into RAM address ($0200 + x)
INX ; X = X + 1
CPX #$10 ; Compare X to hex $20, decimal 16
BNE LoadSpritesLoop ; Branch to LoadSpritesLoop if compare was Not Equal to zero
; if compare was equal to 16, keep going down
InitializeNametables:
LDA #$01
STA nametable
LDA #$00
STA scroll
STA columnNumber
InitializeNametablesLoop:
JSR DrawNewColumn ; draw bg column
LDA scroll ; go to next column
CLC
ADC #$08
STA scroll
INC columnNumber
LDA columnNumber ; repeat for first nametable
CMP #$20
BNE InitializeNametablesLoop
LDA #$00
STA nametable
LDA #$00
STA scroll
JSR DrawNewColumn ; draw first column of second nametable
INC columnNumber
LDA #$00 ; set back to increment +1 mode
STA $2000
InitializeNametablesDone:
InitializeAttributes:
LDA #$01
STA nametable
LDA #$00
STA scroll
STA columnNumber
InitializeAttributesLoop:
JSR DrawNewAttributes ; draw attribs
LDA scroll ; go to next column
CLC
ADC #$20
STA scroll
LDA columnNumber ; repeat for first nametable
CLC
ADC #$04
STA columnNumber
CMP #$20
BNE InitializeAttributesLoop
LDA #$00
STA nametable
LDA #$00
STA scroll
JSR DrawNewAttributes ; draw first column of second nametable
InitializeAttributesDone:
LDA #$21
STA columnNumber
LDA #%10010000 ; enable NMI, sprites from Pattern Table 0, background from Pattern Table 1
STA $2000
LDA #%00011110 ; enable sprites, enable background, no clipping on left side
STA $2001
Forever:
JMP Forever ;jump back to Forever, infinite loop
NMI:
INC scroll ; add one to our scroll variable each frame
NTSwapCheck:
LDA scroll ; check if the scroll just wrapped from 255 to 0
BNE NTSwapCheckDone
NTSwap:
LDA nametable ; load current nametable number (0 or 1)
EOR #$01 ; exclusive OR of bit 0 will flip that bit
STA nametable ; so if nametable was 0, now 1
; if nametable was 1, now 0
NTSwapCheckDone:
NewAttribCheck:
LDA scroll
AND #%00011111 ; check for multiple of 32
BNE NewAttribCheckDone ; if low 5 bits = 0, time to write new attribute bytes
jsr DrawNewAttributes
NewAttribCheckDone:
NewColumnCheck:
LDA scroll
AND #%00000111 ; throw away higher bits to check for multiple of 8
BNE NewColumnCheckDone ; done if lower bits != 0
JSR DrawNewColumn ; if lower bits = 0, time for new column
lda columnNumber
clc
adc #$01 ; go to next column
and #%01111111 ; only 128 columns of data, throw away top bit to wrap
sta columnNumber
NewColumnCheckDone:
LDA #$00
STA $2003
LDA #$02
STA $4014 ; sprite DMA from $0200
; run other game graphics updating code here
LDA #$00
STA $2006 ; clean up PPU address registers
STA $2006
LDA scroll
STA $2005 ; write the horizontal scroll count register
LDA #$00 ; no vertical scrolling
STA $2005
;;This is the PPU clean up section, so rendering the next frame starts properly.
LDA #%10010000 ; enable NMI, sprites from Pattern Table 0, background from Pattern Table 1
ORA nametable ; select correct nametable for bit 0
STA $2000
LDA #%00011110 ; enable sprites, enable background, no clipping on left side
STA $2001
; run normal game engine code here
; reading from controllers, etc
RTI ; return from interrupt
DrawNewColumn:
LDA scroll ; calculate new column address using scroll register
LSR A
LSR A
LSR A ; shift right 3 times = divide by 8
STA columnLow ; $00 to $1F, screen is 32 tiles wide
LDA nametable ; calculate new column address using current nametable
EOR #$01 ; invert low bit, A = $00 or $01
ASL A ; shift up, A = $00 or $02
ASL A ; $00 or $04
CLC
ADC #$20 ; add high byte of nametable base address ($2000)
STA columnHigh ; now address = $20 or $24 for nametable 0 or 1
LDA columnNumber ; column number * 32 = column data offset
ASL A
ASL A
ASL A
ASL A
ASL A
STA sourceLow
LDA columnNumber
LSR A
LSR A
LSR A
STA sourceHigh
LDA sourceLow ; column data start + offset = address to load column data from
CLC
ADC #LOW(columnData) ; ADC #LOW(columnData)
STA sourceLow
LDA sourceHigh
ADC #HIGH(columnData) ; ADC #HIGH(columnData)
STA sourceHigh
DrawColumn:
LDA #%00000100 ; set to increment +32 mode
STA $2000
LDA $2002 ; read PPU status to reset the high/low latch
LDA columnHigh ; LDA columnHigh
STA $2006 ; write the high byte of column address
LDA columnLow ; LDA columnLow
STA $2006 ; write the low byte of column address
LDX #$1E ; copy 30 bytes
LDY #$00 ; LDY #$00
DrawColumnLoop:
LDA [sourceLow], y
STA $2007
INY
DEX
BNE DrawColumnLoop
RTS
DrawNewAttributes:
LDA nametable
EOR #$01 ; invert low bit, A = $00 or $01
ASL A ; shift up, A = $00 or $02
ASL A ; $00 or $04
CLC
ADC #$23 ; add high byte of attribute base address ($23C0)
STA columnHigh ; now address = $23 or $27 for nametable 0 or 1
LDA scroll
LSR A
LSR A
LSR A
LSR A
LSR A
CLC
ADC #$C0
STA columnLow ; attribute base + scroll / 32
LDA columnNumber ; (column number / 4) * 8 = column data offset
AND #%11111100
ASL A
STA sourceLow
LDA columnNumber
LSR A
LSR A
LSR A
LSR A
LSR A
LSR A
LSR A
STA sourceHigh
LDA sourceLow ; column data start + offset = address to load column data from
CLC
ADC #LOW(attribData)
STA sourceLow
LDA sourceHigh
ADC #HIGH(attribData)
STA sourceHigh
LDY #$00
LDA $2002 ; read PPU status to reset the high/low latch
DrawNewAttributesLoop
LDA columnHigh
STA $2006 ; write the high byte of column address
LDA columnLow
STA $2006 ; write the low byte of column address
LDA [sourceLow], y ; copy new attribute byte
STA $2007
INY
CPY #$08 ; copy 8 attribute bytes
BEQ DrawNewAttributesLoopDone
LDA columnLow ; next attribute byte is at address + 8
CLC
ADC #$08
STA columnLow
JMP DrawNewAttributesLoop
DrawNewAttributesLoopDone:
rts
;;;;;;;;;;;;;;
.bank 1
.org $E000
palette:
.db $22,$29,$1A,$0F, $22,$36,$17,$0F, $22,$30,$21,$0F, $22,$27,$17,$0F ;;background palette
.db $22,$16,$27,$18, $22,$1A,$30,$27, $22,$16,$30,$27, $22,$0F,$36,$17 ;;sprite palette
sprites:
;vert tile attr horiz
.db $80, $32, $00, $80 ;sprite 0
.db $80, $33, $00, $88 ;sprite 1
.db $88, $34, $00, $80 ;sprite 2
.db $88, $35, $00, $88 ;sprite 3
columnData:
.incbin "SMBlevel.bin"
attribData:
.incbin "SMBattrib.bin"
.org $FFFA ;first of the three vectors starts here
.dw NMI ;when an NMI happens (once per frame if enabled) the
;processor will jump to the label NMI:
.dw RESET ;when the processor first turns on or is reset, it will jump
;to the label RESET:
.dw 0 ;external interrupt IRQ is not used in this tutorial
;;;;;;;;;;;;;;
.bank 2
.org $0000
.incbin "mario.chr" ;includes 8KB graphics file from SMB1
