Hi again guys!
I'm trying to modify Advanced Nerdy Nights #3 scroll code in order to scroll only when you press right and sprite moves right. It kinda works but looks like every X iterations nametable number switches for a moment and wrong nametable background is displayed for a fraction of time. You can see it downloading the rom following this link. Im using NESASM and FCEUXD emulator.
http://s000.tinyupload.com/?file_id=132 ... 2808043245
I've checked places in code where nametable number is switched but I can't find whats wrong, The code is as follows
Thanks for your help!
I'm trying to modify Advanced Nerdy Nights #3 scroll code in order to scroll only when you press right and sprite moves right. It kinda works but looks like every X iterations nametable number switches for a moment and wrong nametable background is displayed for a fraction of time. You can see it downloading the rom following this link. Im using NESASM and FCEUXD emulator.
http://s000.tinyupload.com/?file_id=132 ... 2808043245
I've checked places in code where nametable number is switched but I can't find whats wrong, The code is as follows
Code:
.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:
FillAttrib0:
LDA $2002 ; read PPU status to reset the high/low latch
LDA #$23
STA $2006 ; write the high byte of $23C0 address (nametable 0 attributes)
LDA #$C0
STA $2006 ; write the low byte of $23C0 address
LDX #$40 ; fill 64 bytes
LDA #$00
FillAttrib0Loop:
STA $2007
DEX
BNE FillAttrib0Loop
FillAttrib1:
LDA $2002 ; read PPU status to reset the high/low latch
LDA #$27
STA $2006 ; write the high byte of $27C0 address (nametable 1 attributes)
LDA #$C0
STA $2006 ; write the low byte of $27C0 address
LDX #$40 ; fill 64 bytes
LDA #$FF
FillAttrib1Loop:
STA $2007
DEX
BNE FillAttrib1Loop
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:
;JMP AutoScroll
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
LatchController:
LDA #$01
STA $4016
LDA #$00
STA $4016 ; tell both the controllers to latch buttons
LDA $4016
LDA $4016
LDA $4016
LDA $4016
LDA $4016
LDA $4016
LDA $4016
LDA $4016 ; player 1 - right
AND #%00000001 ; only look at bit 0
BEQ ReadRightDone ; branch to ReadADone if button is NOT pressed (0)
; add instructions here to do something when button IS pressed (1)
LDY #$00
LoopR:
LDA $0203, y
CLC
ADC #$01
STA $0203,y
INY
INY
INY
INY
CPY #$10
BNE LoopR
INC scroll
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:
NewColumnCheck:
LDA scroll
AND #%00000111 ; throw away higher bits
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:
ReadRightDone:
RTI ; return from interrupt
AutoScroll:
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
AND #%11111000
LSR A
LSR A
LSR A
STA sourceHigh
LDA sourceLow ; column data start + offset = address to load column data from
CLC
ADC #LOW(columnData)
STA sourceLow
LDA sourceHigh
ADC #HIGH(columnData)
STA sourceHigh
DrawColumn:
LDA #%10010100 ; set to increment +32 mode
STA $2000
LDA $2002 ; read PPU status to reset the high/low latch
LDA columnHigh
STA $2006 ; write the high byte of column address
LDA columnLow
STA $2006 ; write the low byte of column address
LDX #$1E ; copy 30 bytes
LDY #$00
DrawColumnLoop:
LDA [sourceLow], y
STA $2007
INY
DEX
BNE DrawColumnLoop
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,$1C,$15,$14, $22,$02,$38,$3C, $22,$1C,$15,$14, $22,$02,$38,$3C ;;sprite palette
sprites:
;vert tile attr horiz
.db $BF, $32, $00, $00 ;sprite 0
.db $BF, $33, $00, $08 ;sprite 1
.db $C7, $34, $00, $00 ;sprite 2
.db $C7, $35, $00, $08 ;sprite 3
columnData:
.incbin "SMBlevel.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
.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:
FillAttrib0:
LDA $2002 ; read PPU status to reset the high/low latch
LDA #$23
STA $2006 ; write the high byte of $23C0 address (nametable 0 attributes)
LDA #$C0
STA $2006 ; write the low byte of $23C0 address
LDX #$40 ; fill 64 bytes
LDA #$00
FillAttrib0Loop:
STA $2007
DEX
BNE FillAttrib0Loop
FillAttrib1:
LDA $2002 ; read PPU status to reset the high/low latch
LDA #$27
STA $2006 ; write the high byte of $27C0 address (nametable 1 attributes)
LDA #$C0
STA $2006 ; write the low byte of $27C0 address
LDX #$40 ; fill 64 bytes
LDA #$FF
FillAttrib1Loop:
STA $2007
DEX
BNE FillAttrib1Loop
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:
;JMP AutoScroll
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
LatchController:
LDA #$01
STA $4016
LDA #$00
STA $4016 ; tell both the controllers to latch buttons
LDA $4016
LDA $4016
LDA $4016
LDA $4016
LDA $4016
LDA $4016
LDA $4016
LDA $4016 ; player 1 - right
AND #%00000001 ; only look at bit 0
BEQ ReadRightDone ; branch to ReadADone if button is NOT pressed (0)
; add instructions here to do something when button IS pressed (1)
LDY #$00
LoopR:
LDA $0203, y
CLC
ADC #$01
STA $0203,y
INY
INY
INY
INY
CPY #$10
BNE LoopR
INC scroll
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:
NewColumnCheck:
LDA scroll
AND #%00000111 ; throw away higher bits
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:
ReadRightDone:
RTI ; return from interrupt
AutoScroll:
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
AND #%11111000
LSR A
LSR A
LSR A
STA sourceHigh
LDA sourceLow ; column data start + offset = address to load column data from
CLC
ADC #LOW(columnData)
STA sourceLow
LDA sourceHigh
ADC #HIGH(columnData)
STA sourceHigh
DrawColumn:
LDA #%10010100 ; set to increment +32 mode
STA $2000
LDA $2002 ; read PPU status to reset the high/low latch
LDA columnHigh
STA $2006 ; write the high byte of column address
LDA columnLow
STA $2006 ; write the low byte of column address
LDX #$1E ; copy 30 bytes
LDY #$00
DrawColumnLoop:
LDA [sourceLow], y
STA $2007
INY
DEX
BNE DrawColumnLoop
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,$1C,$15,$14, $22,$02,$38,$3C, $22,$1C,$15,$14, $22,$02,$38,$3C ;;sprite palette
sprites:
;vert tile attr horiz
.db $BF, $32, $00, $00 ;sprite 0
.db $BF, $33, $00, $08 ;sprite 1
.db $C7, $34, $00, $00 ;sprite 2
.db $C7, $35, $00, $08 ;sprite 3
columnData:
.incbin "SMBlevel.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
Thanks for your help!
