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Merge branch 'feature/nmi'
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tyfkda committed Mar 17, 2024
2 parents a50e4a8 + 5274971 commit 11c459d
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Showing 6 changed files with 53 additions and 30 deletions.
2 changes: 1 addition & 1 deletion src/app/js_powered_app.ts
Original file line number Diff line number Diff line change
Expand Up @@ -158,7 +158,7 @@ export class JsApp extends App {
this.jsNes.update()
this.updateAudio()

for (let i = VBlank.START; i <= VBlank.END; ++i) {
for (let i = VBlank.NMI; i <= VBlank.END; ++i) {
this.jsNes.setHcount(i)
}
}
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29 changes: 18 additions & 11 deletions src/nes/cpu/cpu.ts
Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,7 @@ export class Cpu {
private carry: Bit = 0

private pc: Address // Program counter
private nmiRequest = -1
private irqRequest = 0
private stallCycles = 0

Expand Down Expand Up @@ -128,17 +129,8 @@ export class Cpu {
}

// Non-maskable interrupt
public nmi(): void {
const vector = this.read16(VEC_NMI)
if (this.breakPoints.has(BreakType.NMI)) {
this.paused = true
console.warn(`paused because NMI: ${Util.hex(this.pc, 4)}, ${Util.hex(vector, 4)}`)
}

this.push16(this.pc)
this.push(this.getStatusReg() & ~BREAK_FLAG)
this.pc = vector
this.irqBlocked = 1
public requestNmi(): void {
this.nmiRequest = 2 // TODO: confirm.
}

public requestIrq(type: IrqType): void {
Expand All @@ -154,6 +146,21 @@ export class Cpu {
}

public step(): number {
if (this.nmiRequest >= 0) {
if (--this.nmiRequest < 0) {
const vector = this.read16(VEC_NMI)
this.push16(this.pc)
this.push(this.getStatusReg() & ~BREAK_FLAG)
this.pc = vector
this.irqBlocked = 1

if (this.breakPoints.has(BreakType.NMI)) {
this.paused = true
console.warn(`paused because NMI: ${Util.hex(this.pc, 4)}, ${Util.hex(vector, 4)}`)
return 0
}
}
}
if (this.irqRequest !== 0 && this.irqBlocked === 0) {
this.irqRequest = 0
this.handleIrq()
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2 changes: 1 addition & 1 deletion src/nes/mapper/mapper005.ts
Original file line number Diff line number Diff line change
Expand Up @@ -124,7 +124,7 @@ export class Mapper005 extends Mapper {
// Note: BGs OR sprites MUST be enabled in $2001 (bits 3 and 4)
// in order for the countdown to occur.
const regs = this.options.getPpuRegs()
this.ppuInFrame = hcount < VBlank.START && (regs[PpuReg.MASK] & (PpuMaskBit.SHOW_SPRITE | PpuMaskBit.SHOW_BG)) !== 0
this.ppuInFrame = hcount < VBlank.NMI && (regs[PpuReg.MASK] & (PpuMaskBit.SHOW_SPRITE | PpuMaskBit.SHOW_BG)) !== 0
if (this.ppuInFrame && this.irqHlineEnable && this.irqHlineCompare === hcount && hcount !== 0) {
this.options.requestIrq(IrqType.EXTERNAL)
}
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4 changes: 2 additions & 2 deletions src/nes/nes.ts
Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,7 @@ export class Nes {
constructor(opt?: NesOption) {
this.bus = new Bus()
this.cpu = new Cpu(this.bus)
this.ppu = new Ppu(opt?.nmiFn || this.cpu.nmi.bind(this.cpu))
this.ppu = new Ppu(opt?.nmiFn || this.cpu.requestNmi.bind(this.cpu))
this.apu = new Apu(this.gamePads, opt?.apuIrqFn || (() => this.cpu.requestIrq(IrqType.APU)))
this.eventCallback = (_e, _p) => {}
this.breakPointCallback = () => {}
Expand Down Expand Up @@ -301,7 +301,7 @@ export class Nes {
this.apu.onHblank(hcount)
this.mapper.onHblank(hcount)

if (hcount === VBlank.START)
if (hcount === VBlank.NMI)
this.eventCallback(NesEvent.VBlank, (leftCycles / VCYCLE) | 0)
}
this.cycleCount = nextCycleCount
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23 changes: 19 additions & 4 deletions src/nes/ppu/ppu.ts
Original file line number Diff line number Diff line change
Expand Up @@ -285,6 +285,7 @@ export class Ppu {
value &= ~(PpuStatusBit.VBLANK | PpuStatusBit.SPRITE0HIT | PpuStatusBit.SPRITE_OVERFLOW)
}

const before = this.regs[reg]
this.regs[reg] = value

switch (reg as PpuReg) {
Expand All @@ -295,6 +296,11 @@ export class Ppu {
this.ppuAddr = ((this.ppuAddr & ~0x0c00) |
((value & PpuCtrlBit.BASE_NAMETABLE_ADDRESS) << 10))
this.updateCoarseX()

if ((value & PpuCtrlBit.VINT_ENABLE) !== 0 &&
(before & PpuCtrlBit.VINT_ENABLE) === 0 &&
(this.regs[PpuReg.STATUS] & PpuStatusBit.VBLANK))
this.triggerNmi()
}
break
case PpuReg.MASK:
Expand Down Expand Up @@ -373,11 +379,20 @@ export class Ppu {
this.checkSprite0Hit(hcount)

switch (hcount) {
case VBlank.START:
this.setVBlank()
break
// case VBlank.START:
// > Post-render scanline
// > The PPU just idles during this scanline. Even though accessing PPU memory
// > from the program would be safe here, the VBlank flag isn't set until after
// > this scanline.
// break
case VBlank.NMI:
if ((this.regs[PpuReg.CTRL] & PpuCtrlBit.VINT_ENABLE) !== 0)
// > Vertical blanking lines (241-260)
// > The VBlank flag of the PPU is set at tick 1 (the second tick) of scanline
// > 241, where the VBlank NMI also occurs. The PPU makes no memory accesses
// > during these scanlines, so PPU memory can be freely accessed by the program.
this.setVBlank()
if ((this.regs[PpuReg.CTRL] & PpuCtrlBit.VINT_ENABLE) !== 0 &&
(this.regs[PpuReg.STATUS] & PpuStatusBit.VBLANK) !== 0)
this.triggerNmi()
break
case VBlank.END:
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23 changes: 12 additions & 11 deletions test/nes/cpu/cpu.spec.ts
Original file line number Diff line number Diff line change
Expand Up @@ -25,17 +25,18 @@ describe('cpu', () => {
expect(cpu.getRegs().pc).toBe(0xabcd)
})

it('NMI', () => {
const cpu = new Cpu(new MappedBus({
0xfffa: 0x76,
0xfffb: 0x98,
0xfffc: 0xcd,
0xfffd: 0xab,
}))
cpu.reset()
cpu.nmi()
expect(cpu.getRegs().pc).toBe(0x9876)
})
// it('NMI', () => {
// const cpu = new Cpu(new MappedBus({
// 0xfffa: 0x76,
// 0xfffb: 0x98,
// 0xfffc: 0xcd,
// 0xfffd: 0xab,
// }))
// cpu.reset()
// cpu.requestNmi()
// cpu.step()
// expect(cpu.getRegs().pc).toBe(0x9876)
// })

it('IRQ', () => {
const cpu = new Cpu(new MappedBus({
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