add new mapper, 004_0 MMC3

2 files changed, 224 insertions, 0 deletions

diff --git a/mappers/mapper_004_0.c b/mappers/mapper_004_0.c
new file mode 100644
index 0000000..34970d6
--- /dev/null
+++ b/mappers/mapper_004_0.c
@@ -0,0 +1,207 @@
+
+
+__attribute__((always_inline))
+static inline void mapper_004_0_update_prg_banks(struct nes_state *state) {
+	struct mapper_004_0 *mapper = &state->mapper_data.m004_0;
+
+	uint32_t prg_bank_count = state->ines.prg_size / 0x2000;
+	uint8_t r6 = mapper->bank_registers[6] & (prg_bank_count - 1);
+	uint8_t r7 = mapper->bank_registers[7] & (prg_bank_count - 1);
+	uint8_t last_bank = (prg_bank_count - 1);
+	uint8_t second_last = (prg_bank_count - 2);
+
+	if(mapper->bank_select & 0x40) {
+		// PRG mode 1: $c000 swappable, $8000 fixed to second-last
+		mapper->prg_banks[0] = state->prg_rom + (second_last * 0x2000);
+		mapper->prg_banks[1] = state->prg_rom + (r7 * 0x2000);
+		mapper->prg_banks[2] = state->prg_rom + (r6 * 0x2000);
+		mapper->prg_banks[3] = state->prg_rom + (last_bank * 0x2000);
+	} else {
+		// PRG mode 0: $8000 swappable, $c000 fixed to second-last
+		mapper->prg_banks[0] = state->prg_rom + (r6 * 0x2000);
+		mapper->prg_banks[1] = state->prg_rom + (r7 * 0x2000);
+		mapper->prg_banks[2] = state->prg_rom + (second_last * 0x2000);
+		mapper->prg_banks[3] = state->prg_rom + (last_bank * 0x2000);
+	}
+}
+
+__attribute__((always_inline))
+static inline void mapper_004_0_update_chr_banks(struct nes_state *state) {
+	struct mapper_004_0 *mapper = &state->mapper_data.m004_0;
+
+	if(!state->ines.chr_size) {
+		return;
+	}
+
+	uint32_t chr_bank_count = state->ines.chr_size / 0x400;
+
+	if(mapper->bank_select & 0x80) {
+		// CHR mode 1: four 1kb banks at $0000, two 2kb banks at $1000
+		mapper->chr_banks[0] = state->chr_rom + ((mapper->bank_registers[2] & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[1] = state->chr_rom + ((mapper->bank_registers[3] & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[2] = state->chr_rom + ((mapper->bank_registers[4] & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[3] = state->chr_rom + ((mapper->bank_registers[5] & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[4] = state->chr_rom + (((mapper->bank_registers[0] & 0xfe) & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[5] = state->chr_rom + (((mapper->bank_registers[0] | 0x01) & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[6] = state->chr_rom + (((mapper->bank_registers[1] & 0xfe) & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[7] = state->chr_rom + (((mapper->bank_registers[1] | 0x01) & (chr_bank_count - 1)) * 0x400);
+	} else {
+		// CHR mode 0: two 2kb banks at $0000, four 1kb banks at $1000
+		mapper->chr_banks[0] = state->chr_rom + (((mapper->bank_registers[0] & 0xfe) & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[1] = state->chr_rom + (((mapper->bank_registers[0] | 0x01) & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[2] = state->chr_rom + (((mapper->bank_registers[1] & 0xfe) & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[3] = state->chr_rom + (((mapper->bank_registers[1] | 0x01) & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[4] = state->chr_rom + ((mapper->bank_registers[2] & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[5] = state->chr_rom + ((mapper->bank_registers[3] & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[6] = state->chr_rom + ((mapper->bank_registers[4] & (chr_bank_count - 1)) * 0x400);
+		mapper->chr_banks[7] = state->chr_rom + ((mapper->bank_registers[5] & (chr_bank_count - 1)) * 0x400);
+	}
+}
+
+static uint8_t mapper_004_0_prg_rom_read(struct nes_state *state, uint32_t addr) {
+	struct mapper_004_0 *mapper = &state->mapper_data.m004_0;
+	uint32_t bank = (addr >> 13) & 3;
+	return mapper->prg_banks[bank][addr & 0x1fff];
+}
+
+static void mapper_004_0_prg_rom_write(struct nes_state *state, uint32_t addr, uint8_t value) {
+	struct mapper_004_0 *mapper = &state->mapper_data.m004_0;
+
+	if(addr >= 0x8000 && addr <= 0x9fff) {
+		if(addr & 1) {
+			// $8001/$9fff (odd): bank data
+			uint8_t reg = mapper->bank_select & 7;
+			mapper->bank_registers[reg] = value;
+
+			if(reg <= 5) {
+				mapper_004_0_update_chr_banks(state);
+			} else {
+				mapper_004_0_update_prg_banks(state);
+			}
+		} else {
+			// $8000/$9ffe (even): bank select
+			mapper->bank_select = value;
+			mapper_004_0_update_prg_banks(state);
+			mapper_004_0_update_chr_banks(state);
+		}
+	} else if(addr >= 0xa000 && addr <= 0xbfff) {
+		if(addr & 1) {
+			// $a001/$bfff (odd): prg ram protect (ignored for now)
+		} else {
+			// $a000/$bffe (even): mirroring
+			mapper->mirroring = value & 1;
+		}
+	} else if(addr >= 0xc000 && addr <= 0xdfff) {
+		if(addr & 1) {
+			// $c001/$dfff (odd): irq reload
+			mapper->irq_counter = 0;
+			mapper->irq_reload = 1;
+		} else {
+			// $c000/$dffe (even): irq latch
+			mapper->irq_latch = value;
+		}
+	} else if(addr >= 0xe000) {
+		if(addr & 1) {
+			// $e001/$ffff (odd): irq enable
+			mapper->irq_enabled = 1;
+		} else {
+			// $e000/$fffe (even): irq disable
+			mapper->irq_enabled = 0;
+			state->cpu.irq_pending = 0;
+		}
+	}
+}
+
+static uint8_t mapper_004_0_chr_read(struct nes_state *state, uint32_t addr) {
+	struct mapper_004_0 *mapper = &state->mapper_data.m004_0;
+
+	if(state->ines.chr_size == 0) {
+		return state->chr_ram[addr];
+	}
+
+	uint32_t bank = (addr >> 10) & 7;
+	return mapper->chr_banks[bank][addr & 0x3ff];
+}
+
+static void mapper_004_0_chr_write(struct nes_state *state, uint32_t addr, uint8_t value) {
+	state->chr_ram[addr] = value;
+}
+
+static uint8_t mapper_004_0_prg_ram_read(struct nes_state *state, uint32_t addr) {
+	return state->sram[addr & 0x1fff];
+}
+
+static void mapper_004_0_prg_ram_write(struct nes_state *state, uint32_t addr, uint8_t value) {
+	state->sram[addr & 0x1fff] = value;
+}
+
+static uint8_t mapper_004_0_ciram_read(struct nes_state *state, uint32_t addr) {
+	struct mapper_004_0 *mapper = &state->mapper_data.m004_0;
+
+	if(mapper->mirroring == 0) {
+		// vertical
+		return state->ciram[addr & 0x7ff];
+	} else {
+		// horizontal
+		return state->ciram[((addr >> 1) & 0x400) | (addr & 0x3ff)];
+	}
+}
+
+static void mapper_004_0_ciram_write(struct nes_state *state, uint32_t addr, uint8_t value) {
+	struct mapper_004_0 *mapper = &state->mapper_data.m004_0;
+
+	if(mapper->mirroring == 0) {
+		// vertical
+		state->ciram[addr & 0x7ff] = value;
+	} else {
+		// horizontal
+		state->ciram[((addr >> 1) & 0x400) | (addr & 0x3ff)] = value;
+	}
+}
+
+static void mapper_004_0_tick(struct nes_state *state) {
+	struct mapper_004_0 *mapper = &state->mapper_data.m004_0;
+
+	// clock IRQ counter once per scanline at dot 260
+	// this approximates the filtered A12 behavior
+	if(state->ppu.dot == 260 && state->ppu.scanline < 240) {
+		if(mapper->irq_counter == 0 || mapper->irq_reload) {
+			mapper->irq_counter = mapper->irq_latch;
+			if(mapper->irq_reload) {
+				mapper->irq_reload = 0;
+			}
+		} else {
+			mapper->irq_counter--;
+			if(mapper->irq_counter == 0 && mapper->irq_enabled) {
+				state->cpu.irq_pending = 1;
+			}
+		}
+	}
+}
+
+static void mapper_004_0_init(struct nes_state *state) {
+	struct mapper_004_0 *mapper = &state->mapper_data.m004_0;
+
+	memset(mapper, 0, sizeof(struct mapper_004_0));
+
+	mapper_004_0_update_prg_banks(state);
+
+	if(state->ines.chr_size) {
+		mapper_004_0_update_chr_banks(state);
+	} else {
+		// chr-ram: point all banks to chr_ram
+		for(int i = 0; i < 8; i++) {
+			mapper->chr_banks[i] = state->chr_ram + (i * 0x400);
+		}
+	}
+
+	state->mapper_function.prg_rom_read = mapper_004_0_prg_rom_read;
+	state->mapper_function.prg_rom_write = mapper_004_0_prg_rom_write;
+	state->mapper_function.prg_ram_read = mapper_004_0_prg_ram_read;
+	state->mapper_function.prg_ram_write = mapper_004_0_prg_ram_write;
+	state->mapper_function.chr_read = mapper_004_0_chr_read;
+	state->mapper_function.chr_write = mapper_004_0_chr_write;
+	state->mapper_function.ciram_read = mapper_004_0_ciram_read;
+	state->mapper_function.ciram_write = mapper_004_0_ciram_write;
+	state->mapper_function.tick = mapper_004_0_tick;
+}
diff --git a/mappers/mapper_004_0.h b/mappers/mapper_004_0.h
new file mode 100644
index 0000000..227d8b8
--- /dev/null
+++ b/mappers/mapper_004_0.h
@@ -0,0 +1,17 @@
+
+
+struct mapper_004_0 {
+	uint8_t *prg_banks[4];		// 8kb banks at $8000, $a000, $c000, $e000
+	uint8_t *chr_banks[8];		// 1kb banks at $0000-$1fff
+
+	uint8_t bank_select;
+	uint8_t bank_registers[8];
+	uint8_t mirroring;
+
+	uint8_t irq_latch;
+	uint8_t irq_counter;
+	uint8_t irq_reload;
+	uint8_t irq_enabled;
+
+	uint8_t last_a12;
+} __attribute__((packed, aligned(64)));