added scaffolding for apu

5 files changed, 226 insertions, 23 deletions

diff --git a/apu.c b/apu.c
new file mode 100644
index 0000000..0c16123
--- /dev/null
+++ b/apu.c
@@ -0,0 +1,164 @@
+
+
+static inline void ppu_tick(struct nes_state *state);
+static inline uint8_t memory_read(struct nes_state *state, uint32_t offset);
+
+// DMC frequency table (NTSC)
+static const uint16_t dmc_rate_table[16] = {
+	428, 380, 340, 320, 286, 254, 226, 214,
+	190, 160, 142, 128, 106,  85,  72,  54
+};
+
+// $4015 write
+static void apu_write4015(struct nes_state *state, uint8_t val) {
+	struct apu_state *apu = &state->apu;
+
+	if(val & 0x10) {
+		if(!apu->dmc_dma_enabled || apu->dmc_bytes_remaining == 0) {
+			apu->dmc_current_addr = 0xC000 + ((uint16_t)apu->dmc_sample_addr << 6);
+			apu->dmc_bytes_remaining = ((uint16_t)apu->dmc_sample_len << 4);
+		}
+		apu->dmc_dma_enabled = 1;
+	} else {
+		apu->dmc_dma_enabled = 0;
+	}
+}
+
+// $4015 read
+static uint8_t apu_read4015(struct nes_state *state) {
+	struct apu_state *apu = &state->apu;
+	uint8_t result = 0;
+
+	if(apu->dmc_bytes_remaining > 0) {
+		result |= 0x10;
+	}
+	if(apu->irq_pending) {
+		result |= 0x40;
+		apu->irq_pending = 0;
+	}
+	return result;
+}
+
+// $4010–$4013, $4015 write
+static void apu_write(struct nes_state *state, uint16_t addr, uint8_t val) {
+	struct apu_state *apu = &state->apu;
+
+	switch(addr) {
+		case 0x4010: {
+			apu->dmc_irq_enable = (val >> 7) & 1;
+			apu->dmc_loop_flag = (val >> 6) & 1;
+			apu->dmc_freq_index = val & 0x0F;
+		} break;
+		case 0x4011: {
+			// DAC write ignored
+		} break;
+		case 0x4012: {
+			apu->dmc_sample_addr = val;
+		} break;
+		case 0x4013: {
+			apu->dmc_sample_len = val;
+		} break;
+		case 0x4015: {
+			apu_write4015(state, val);
+		} break;
+	}
+}
+
+// APU tick
+static inline void apu_tick(struct nes_state *state) {
+	struct apu_state *apu = &state->apu;
+
+	apu->frame_cycle++;
+
+	if(apu->mode == 0) {
+		if(apu->frame_cycle == 7457) {
+			// Quarter frame
+		} else if(apu->frame_cycle == 14913) {
+			// Quarter frame
+			// Half frame
+		} else if(apu->frame_cycle == 22371) {
+			// Quarter frame
+		} else if(apu->frame_cycle == 29829) {
+			// Half frame
+			if(!apu->irq_inhibit) {
+				apu->irq_pending = 1;
+			}
+		} else if(apu->frame_cycle >= 29830) {
+			apu->frame_cycle = 0;
+		}
+	} else {
+		if(apu->frame_cycle == 7457) {
+			// Quarter frame
+		} else if(apu->frame_cycle == 14913) {
+			// Quarter frame
+			// Half frame
+		} else if(apu->frame_cycle == 22371) {
+			// Quarter frame
+		} else if(apu->frame_cycle == 29829) {
+			// Half frame
+		} else if(apu->frame_cycle == 37281) {
+			// Quarter frame
+		} else if(apu->frame_cycle >= 37282) {
+			apu->frame_cycle = 0;
+		}
+	}
+
+	// if(apu->mode == 0) {
+	// 	if(apu->frame_cycle == 7457 || apu->frame_cycle == 14913 || apu->frame_cycle == 22371) {
+	// 		// Quarter frame
+	// 	}
+	// 	if(apu->frame_cycle == 14913 || apu->frame_cycle == 29829) {
+	// 		// Half frame
+	// 	}
+	// 	if(apu->frame_cycle == 29829 && !apu->irq_inhibit) {
+	// 		apu->irq_pending = 1;
+	// 	}
+	// 	if(apu->frame_cycle >= 29830) {
+	// 		apu->frame_cycle = 0;
+	// 	}
+	// } else {
+	// 	if(apu->frame_cycle == 7457 || apu->frame_cycle == 14913 || apu->frame_cycle == 22371 || apu->frame_cycle == 37281) {
+	// 		// Quarter frame
+	// 	}
+	// 	if(apu->frame_cycle == 14913 || apu->frame_cycle == 29829) {
+	// 		// Half frame
+	// 	}
+	// 	if(apu->frame_cycle >= 37282) {
+	// 		apu->frame_cycle = 0;
+	// 	}
+	// }
+
+	if(apu->dmc_dma_enabled && apu->dmc_bytes_remaining > 0) {
+		apu->dmc_sample_timer++;
+		if(apu->dmc_sample_timer >= dmc_rate_table[apu->dmc_freq_index]) {
+			apu->dmc_sample_timer = 0;
+
+			uint8_t val = memory_read(state, apu->dmc_current_addr);
+			(void)val;
+
+			apu->dmc_current_addr++;
+			if(apu->dmc_current_addr == 0x0000) {
+				apu->dmc_current_addr = 0x8000;
+			}
+
+			apu->dmc_bytes_remaining--;
+
+			if(apu->dmc_bytes_remaining == 0) {
+				if(apu->dmc_loop_flag) {
+					apu->dmc_current_addr = 0xC000 + ((uint16_t)apu->dmc_sample_addr << 6);
+					apu->dmc_bytes_remaining = ((uint16_t)apu->dmc_sample_len << 4);
+				} else {
+					if(apu->dmc_irq_enable) {
+						apu->irq_pending = 1;
+					}
+					apu->dmc_dma_enabled = 0;
+				}
+			}
+
+			for(uint32_t i = 0; i < 4; i++) {
+				state->cpu.cycles++;
+				ppu_tick(state);
+			}
+		}
+	}
+}
diff --git a/memory.c b/memory.c
index 1eaf489..db5fcd0 100644
--- a/memory.c
+++ b/memory.c
@@ -1,10 +1,46 @@
 
 
+#if 1
 __attribute__((hot))
 static inline uint8_t memory_read(struct nes_state *state, uint32_t offset) {
 	state->cpu.cycles++;
 	ppu_tick(state);
-	// apu_tick(state);
+	apu_tick(state);
+
+	uint8_t result = 0;
+
+	if(offset >= 0x8000) {	// MOST
+		result = state->mapper_function.prg_rom_read(state, offset);
+
+	} else if(offset < 0x2000) {	// SECOND
+		result = state->ram[offset & 0x07ff];
+
+	} else if(offset < 0x4000) {	// THIRD
+		result = ppu_read(state, offset);
+
+	} else if(offset == 0x4015) {	// APU status
+		result = apu_read4015(state);
+
+	} else if(offset == 0x4016 || offset == 0x4017) {
+		uint32_t index = offset & 1;
+		uint8_t value = (state->ppu.input_latch[index] >> state->ppu.input_bit[index]) & 1;
+		state->ppu.input_bit[index]++;
+		result = value | 0x40;	// Bit 6 open bus high, bit 7 low
+
+	} else if(offset >= 0x6000) {
+		result = state->mapper_function.prg_ram_read(state, offset);
+	}
+
+	return result;
+}
+
+#else
+
+__attribute__((hot))
+static inline uint8_t memory_read(struct nes_state *state, uint32_t offset) {
+	state->cpu.cycles++;
+	ppu_tick(state);
+	apu_tick(state);
 
 	uint8_t result = 0;
 
@@ -29,12 +65,13 @@ static inline uint8_t memory_read(struct nes_state *state, uint32_t offset) {
 
 	return result;
 }
+#endif
 
 __attribute__((hot))
 static inline uint8_t memory_read_dummy(struct nes_state *state, uint32_t offset) {
 	state->cpu.cycles++;
 	ppu_tick(state);
-	// apu_tick(state);
+	apu_tick(state);
 
 	if(offset >= 0x2000 && offset < 0x4000) {
 		return ppu_read(state, offset);
@@ -46,7 +83,7 @@ __attribute__((hot))
 static inline void memory_write(struct nes_state *state, uint32_t offset, uint8_t value) {
 	state->cpu.cycles++;
 	ppu_tick(state);
-	// apu_tick(state);
+	apu_tick(state);
 
 	if(offset < 0x2000) {
 		state->ram[offset & 0x07ff] = value;
@@ -55,32 +92,23 @@ static inline void memory_write(struct nes_state *state, uint32_t offset, uint8_
 		ppu_write(state, offset, value);
 
 	} else if(offset < 0x4018) {
-		// APU + joypad + DMA
 		if(offset == 0x4014) {
 			ppu_dma_4014(state, value);
 
-		// } else if(offset == 0x4015) {	// DMC Enable (APU)
-		// 	state->apu.dmc_dma_enabled = (value & 0x10) ? 1 : 0;
-
 		} else if(offset == 0x4016) {
+			// joypad strobe
 			uint8_t prev = state->ppu.input_strobe;
 			state->ppu.input_strobe = value & 1;
 
 			if(prev == 1 && (value & 1) == 0) {
-				// Latch current inputs
 				state->ppu.input_latch[0] = state->ppu.input[0];
 				state->ppu.input_latch[1] = state->ppu.input[1];
 				state->ppu.input_bit[0] = 0;
 				state->ppu.input_bit[1] = 0;
 			}
 
-		// } else if(offset == 0x4017) {	// Frame Counter (APU)
-		// 	state->apu.mode = (value >> 7) & 1;
-		// 	state->apu.irq_inhibit = (value >> 6) & 1;
-		// 	state->apu.frame_cycle = 0;
-		// 	if(state->apu.irq_inhibit) {
-		// 		state->apu.irq_pending = 0;
-		// 	}
+		} else if(offset >= 0x4010 && offset <= 0x4017) {
+			apu_write(state, offset, value);
 		}
 
 	} else if(offset >= 0x6000) {	// NOTE(peter): Might need to move this upwards when we implement a mapper that has prg_ram_*
diff --git a/mknes.c b/mknes.c
index a2f764c..068bd83 100644
--- a/mknes.c
+++ b/mknes.c
@@ -92,7 +92,7 @@ static uint32_t frames;		// debug information
 // NES core
 #include "mappers/mapper.h"
 #include "mknes.h"
-// #include "apu.c"
+#include "apu.c"
 #include "ppu.c"
 #include "ppu_registers.c"
 #include "memory.c"
@@ -142,11 +142,11 @@ int main(int argc, char **argv) {
 	// ines2_load(nstate, "data/0000/raster_demos/RasterTest3e.NES");
 	// ines2_load(nstate, "data/0000/NEStress.NES");
 	// ines2_load(nstate, "data/0000/Super Mario Bros. (World) (HVC-SM).zip");
-	// ines2_load(nstate, "data/0042/Super Mario Bros. + Duck Hunt (USA).zip");
+	ines2_load(nstate, "data/0042/Super Mario Bros. + Duck Hunt (USA).zip");
 	// ines2_load(nstate, "data/0000/Xevious - The Avenger (USA).zip");
 	// ines2_load(nstate, "data/tv.nes");
 
-	ines2_load(nstate, "data/Life Force (USA).zip");	// 2002
+	// ines2_load(nstate, "data/Life Force (USA).zip");	// 2002
 
 	// ines2_load(nstate, "data/0003/Flipull - An Exciting Cube Game (Japan) (En).zip");
 	// ines2_load(nstate, "data/0003/Friday the 13th (USA).zip");
diff --git a/mknes.h b/mknes.h
index 8d12e95..0ae37f4 100644
--- a/mknes.h
+++ b/mknes.h
@@ -68,11 +68,22 @@ struct ppu_state {
 
 struct apu_state {
 	uint32_t frame_cycle;
+
 	uint8_t mode;
 	uint8_t irq_inhibit;
 	uint8_t irq_pending;
+
+	uint8_t dmc_irq_enable;
+	uint8_t dmc_loop_flag;
 	uint8_t dmc_dma_enabled;
-	uint32_t dmc_sample_timer;
+
+	uint8_t dmc_freq_index;
+	uint8_t dmc_sample_addr;
+	uint8_t dmc_sample_len;
+
+	uint16_t dmc_current_addr;
+	uint16_t dmc_bytes_remaining;
+	uint16_t dmc_sample_timer;
 } __attribute__((packed, aligned(64)));
 
 struct cpu_state {
@@ -110,7 +121,7 @@ struct nes_state {
 	union mapper_data mapper_data;
 	struct cpu_state cpu;
 	struct ines_state ines;
-	// struct apu_state apu;
+	struct apu_state apu;
 
 	uint8_t ram[RAM_SIZE]			__attribute__((aligned(4096)));
 	uint8_t ciram[CIRAM_SIZE]		__attribute__((aligned(4096)));
diff --git a/ppu_registers.c b/ppu_registers.c
index 6217908..8423774 100644
--- a/ppu_registers.c
+++ b/ppu_registers.c
@@ -128,7 +128,7 @@ static inline void ppu_dma_4014(struct nes_state *state, uint8_t page) {
 	for(uint8_t i = 0; i < idle_cycles; i++) {
 		state->cpu.cycles++;
 		ppu_tick(state);
-		// apu_tick(state);
+		apu_tick(state);
 	}
 
 	for(uint32_t i = 0; i < 256; i++) {
@@ -136,12 +136,12 @@ static inline void ppu_dma_4014(struct nes_state *state, uint8_t page) {
 
 		state->cpu.cycles++;
 		ppu_tick(state);
-		// apu_tick(state);
+		apu_tick(state);
 		uint8_t value = memory_read_dma(state, addr);
 
 		state->cpu.cycles++;
 		ppu_tick(state);
-		// apu_tick(state);
+		apu_tick(state);
 
 		ppu_write(state, 4, value);
 	}