[FC][Mapper4][IRQ学习源码]
;;FlameCyclone 20230710
;文件头
;======================================================================
.INESPRG 4 ;16KB PRG 数量
.INESCHR 1 ;8KB CHR 数量
.INESMAP 4 ;mapper 4
.INESMIR 1 ;命名表镜像 0水平 1垂直
;必要条件
;1.持有CHR ROM
;2.背景Tile和精灵Tile必须使用不同的图案表, 如背景图案$0000, 精灵图案$1000
;3.精灵内存(OAM)不为空
;==================================================
;NES端口常量
PPU_CTRL = $2000 ;PPU控制寄存器
PPU_MASK = $2001 ;PPU掩码寄存器
PPU_STATUS = $2002 ;PPU状态寄存器：读取后PPU_SCROLL和PPU_ADDRESS被复位，下一个写到PPU_SCROLL的数据是水平的，写到PPU_ADDRESS的数据是高位
PPU_OAM_ADDR = $2003 ;精灵RAM地址：用来设置通过PPU_OAM_DATA访问的256字节精灵RAM地址。每次访问PPU_OAM_DATA后该地址增加1
PPU_OAM_DATA = $2004 ;精灵RAM数据：用来读/写精灵内存。地址通过PPU_OAM_ADDR来设置，每次访问后地址增加1
PPU_SCROLL = $2005 ;屏幕滚动偏移：第一个写的值会进入垂直滚动寄存器（若>239，被忽略）。第二个值出现在水平滚动寄存器
PPU_ADDRESS = $2006 ;VRAM地址：设置PPU_DATA访问的VRAM地址。第一个写地址的高6位。第二个写低8位。每次访问PPU_DATA后地址增加
PPU_DATA = $2007 ;VRAM数据：用来访问VRAM数据，通过PPU_ADDRESS设置的地址在每次访问之后会增加1或32
OAM_DMA = $4014 ;DMA访问精灵RAM：通过写一个值xx到这个端口，引起CPU内存地址为$xx00－$xxFF的区域传送到精灵内存
APU_STATUS = $4015 ;声音通道切换
JOY1_FRAME = $4016 ;手柄1 + 选通
JOY2_FRAME = $4017 ;手柄2 + 选通
;==================================================
;MMC3端口常量
MMC3_BANK_CTRL = $8000
MMC3_BANK_DATA = $8001
MMC3_MIRRORING = $A000
MMC3_PRG_RAM_PROTECT = $A001
MMC3_IRQ_LATCH = $C000
MMC3_IRQ_RELOAD = $C001
MMC3_IRQ_DISABLE = $E000
MMC3_IRQ_ENABLE = $E001
;==================================================
;程序块配置
BANK_DATA_MASK = $07
;--------------------------------------------------
RESET_BANK = $07
RESET_ADDR = $FC00
;==================================================
;图像块配置
CHR_DATA_BANK = $08
;==================================================
;零页内存地址配置
Use_Ram_Addr = $80
PPU_Ctrl_Buf = Use_Ram_Addr
PPU_Msak_Buf = PPU_Ctrl_Buf + $01
PPU_Scroll_H = PPU_Msak_Buf + $01
PPU_Scroll_V = PPU_Scroll_H + $01
FC_Data_L = PPU_Scroll_V + $01
FC_Data_H = FC_Data_L + $01
FC_Data_Buf = FC_Data_H + $01
;==================================================
GAMEPAD_MERGE_FLAG = $04
Gamepad_Keep = FC_Data_Buf + 1
Gamepad_Once = Gamepad_Keep + 2
Gamepad_Temp = Gamepad_Once + 2
Gamepad_0_State = Gamepad_Temp + 2
Gamepad_1_State = Gamepad_0_State + 1
Gamepad_0_Value = Gamepad_1_State + 1
Gamepad_1_Value = Gamepad_0_Value + 1
Gamepad_Port_Value = Gamepad_1_Value + 1
Gamepad_Merge = Gamepad_Port_Value + 1
;==================================================
IRQ_Index = Gamepad_Merge + $01
;==================================================
;CHR图形数据
;==================================================
.BANK CHR_DATA_BANK
.INCBIN "chr_bank/chr_data.chr"
.BANK RESET_BANK & BANK_DATA_MASK
.ORG RESET_ADDR
;--------------------------------------------------
Attributes_Data
;命名表属性
.DB $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
.DB $50,$50,$50,$50,$50,$50,$50,$50,$FF,$FF,$FF,$FF,$BB,$AA,$AA,$AA
.DB $0F,$0F,$0F,$0F,$0B,$0A,$0A,$0A,$AA,$AA,$AA,$AA,$AA,$AA,$AA,$AA
.DB $AA,$AA,$AA,$AA,$AA,$AA,$AA,$55,$55,$55,$55,$55,$55,$55,$55,$55
;--------------------------------------------------
;调色板数据
Palette_Data
.DB $0F,$27,$20,$0F,$0F,$24,$20,$0F,$0F,$21,$20,$0F,$0F,$25,$20,$0F
.DB $0F,$24,$20,$0F,$0F,$24,$20,$0F,$0F,$24,$20,$0F,$0F,$24,$20,$0F
;==================================================
;命名表初始化
Init_Name_Table
LDA #$20
STA PPU_ADDRESS
LDA #$00
STA PPU_ADDRESS
LDA #$00
LDY #$00
LDX #$10
Init_Name_Table_Write
STA PPU_DATA
INY
BNE Init_Name_Table_Write
DEX
BNE Init_Name_Table_Write
RTS
;==================================================
;调色板初始化
Init_Palette
BIT PPU_STATUS
LDA #$3F
STA PPU_ADDRESS
LDA #$00
STA PPU_ADDRESS
LDX #$00
Init_Palette_Write
LDA Palette_Data,X
STA PPU_DATA
INX
CPX #$20
BCC Init_Palette_Write
RTS
;==================================================
;设置命名表属性
Init_NameTable_Attributes
BIT PPU_STATUS
LDA #$23
STA PPU_ADDRESS
LDA #$C0
STA PPU_ADDRESS
LDX #$00
Init_NameTable_Attributes_Write
LDA Attributes_Data,X
STA PPU_DATA
INX
CPX #$40
BCC Init_NameTable_Attributes_Write
RTS
;==================================================
;初始化命名表文本
Init_Name_Table_Text
BIT PPU_STATUS
LDA #$20
STA PPU_ADDRESS
LDA #$00
STA PPU_ADDRESS
LDA #$00
STA FC_Data_Buf
LDY #30
Init_Name_Table_Text_Write
LDX #32
Init_Name_Table_Text_Write_Char
LDA #'0'
CLC
ADC FC_Data_Buf
STA PPU_DATA
DEX
LDA #$14
STA PPU_DATA
DEX
BNE Init_Name_Table_Text_Write_Char
INC FC_Data_Buf
DEY
BNE Init_Name_Table_Text_Write
RTS
;==============================
Init_OAM_Ram;初始化精灵内存
LDX #$00
LDA #$00
STA PPU_OAM_ADDR
LDA #$F8
Init_OAM_Ram_Write
STA PPU_OAM_DATA
INX
BNE Init_OAM_Ram_Write
RTS
GamepadProcess;手柄处理
JSR GamepadDatacan
LDA <Gamepad_0_Value
STA <Gamepad_0_State
LDA <Gamepad_1_Value
STA <Gamepad_1_State
JSR GamepadDatacan
LDX #$01
GamepadMergeCheck;合并手柄输入检查
LDA <Gamepad_0_Value,X
CMP <Gamepad_0_State,X
BEQ GamepadMergeInput
LDA <Gamepad_Temp,X
STA <Gamepad_0_Value,X
GamepadMergeInput;合并手柄输入
DEX
BPL GamepadMergeCheck
LDA <Gamepad_Merge
AND #GAMEPAD_MERGE_FLAG
BNE GamepadStateProcess
LDA <Gamepad_0_Value
ORA <Gamepad_1_Value
STA <Gamepad_0_Value
GamepadStateProcess;手柄状态处理
LDX #$01
GamepadStateSave;手柄状态保存
LDA <Gamepad_0_Value,X
TAY
EOR <Gamepad_Temp,X
AND <Gamepad_0_Value,X
STA <Gamepad_Once,X
STY <Gamepad_Keep,X
STY <Gamepad_Temp,X
DEX
BPL GamepadStateSave
RTS
GamepadDatacan;手柄数据扫描
LDX #$01
STX $4016
DEX
STX $4016
LDY #$08
GamepadPortScan;手柄端口扫描
LDA $4016
STA <Gamepad_Port_Value
LSR A
ORA <Gamepad_Port_Value
LSR A
ROL <Gamepad_0_Value
LDA $4017
STA <Gamepad_Port_Value
LSR A
ORA <Gamepad_Port_Value
LSR A
ROL <Gamepad_1_Value
DEY
BNE GamepadPortScan
RTS
;==================================================
;PPU处理
PPU_Process
LDA #$00
STA PPU_MASK
BIT PPU_STATUS
LDA #$20
STA PPU_ADDRESS
LDA #$00
STA PPU_ADDRESS
STA PPU_SCROLL
STA PPU_SCROLL
LDA PPU_Msak_Buf
STA PPU_MASK
RTS
;==============================
Time_For_Vblank;延时等待
LDA PPU_STATUS
BPL Time_For_Vblank
RTS
;==================================================
;初始化MMC3
Init_MMC3
STA MMC3_IRQ_DISABLE
;设置MMC3水平镜像
LDA #$01
STA MMC3_MIRRORING
LDX #$05
Init_MMC3_Chr_Bank_Write
STX MMC3_BANK_CTRL
LDA MMC3_Chr_Bank_Data,X
STA MMC3_BANK_DATA
DEX
BPL Init_MMC3_Chr_Bank_Write
RTS
;--------------------------------------------------
MMC3_Chr_Bank_Data
.DB $00,$02,$04,$05,$06,$07
;==================================================
;重置中断处理
ResetProgram
SEI
CLD
LDA #$00
STA PPU_CTRL
STA PPU_MASK
STA PPU_STATUS
STA JOY2_FRAME
STA APU_STATUS
LDA #$C0
STA JOY2_FRAME
;等待vblank
LDX #$02
Vblank_Wait_1
BIT PPU_STATUS
BPL Vblank_Wait_1
Vblank_Wait_2
BIT PPU_STATUS
BMI Vblank_Wait_2
DEX
BNE Vblank_Wait_1
LDX #$FF
TXS
;初始化MMC3
JSR Init_MMC3
;==============================
;RAM初始化
Nes_Ram_Init
LDY #$00
LDX #$08
LDA #$00
STA <$00
STA <$01
Nes_Ram_Init_Write
STA [$00],Y
INY
BNE Nes_Ram_Init_Write
INC <$01
DEX
BNE Nes_Ram_Init_Write
;初始化命名表
JSR Init_Name_Table
;初始化调色板
JSR Init_Palette
;初始化命名表属性
JSR Init_NameTable_Attributes
;初始化精灵内存
JSR Init_OAM_Ram
;在屏幕上写点东西
JSR Init_Name_Table_Text
JSR Time_For_Vblank
;开启PPU控制
LDA #$A8
STA PPU_Ctrl_Buf
STA PPU_CTRL
;开启PPU显示
LDA #$1E
STA PPU_Msak_Buf
CLI
JMP Loop
;==============================
;死循环, 等待NMI中断
Loop
JMP Loop
;==================================================
;NMI中断处理
NmiProgram
PHA
TXA
PHA
TYA
PHA
BIT PPU_STATUS
;关闭PPU控制
LDA #$00
STA PPU_CTRL
;处理PPU
JSR PPU_Process
;开启PPU控制
LDA PPU_Ctrl_Buf
STA PPU_CTRL
;手柄处理
JSR GamepadProcess
LDA #$00
STA IRQ_Index
;启动IRQ中断, 第15条扫描线触发
LDA #15 + 1
STA MMC3_IRQ_LATCH
STA MMC3_IRQ_RELOAD
STA MMC3_IRQ_ENABLE
CLI
PLA
TAY
PLA
TAX
PLA
RTI
;==================================================
;IRQ中断处理
IrqProgram
PHA
TXA
PHA
TYA
PHA
;关闭IRQ
STA MMC3_IRQ_DISABLE
;允许下个IRQ触发
STA MMC3_IRQ_ENABLE
;IRQ处理, 15线后继续触发
LDA #15
STA MMC3_IRQ_LATCH
LDA <IRQ_Index
BNE * + 4
INC <PPU_Scroll_H
;设置屏幕滚动
LDA <IRQ_Index
AND #$01
BEQ Irq_Scroll_Right
Irq_Scroll_Left
BIT PPU_STATUS
LDA <PPU_Scroll_H
STA PPU_SCROLL
STA PPU_SCROLL
JMP Irq_Scroll_Over
Irq_Scroll_Right
SEC
SBC <PPU_Scroll_H
STA PPU_SCROLL
STA PPU_SCROLL
Irq_Scroll_Over
INC <IRQ_Index
LDA <IRQ_Index
CMP #14
BCC * + 5
;关闭IRQ
STA MMC3_IRQ_DISABLE
IrqProgramEnd
PLA
TAY
PLA
TAX
PLA
RTI
;==================================================
;中断表
.ORG $FFFA
.WORD NmiProgram
.WORD ResetProgram
.WORD IrqProgram
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