From 46d0f6aeb1588b85852487e581a8b4c9c2401646 Mon Sep 17 00:00:00 2001
From: Peter Fors <peter.fors@mindkiller.com>
Date: Sun, 2 Nov 2025 13:54:50 +0100
Subject: Add MMC5, not in a working state, but can start castlevania iii, this
 is a horrible mapper to implement.

---
 mappers/mapper_004_0.c |   4 +-
 mappers/mapper_005_0.c | 313 +++++++++++++++++++++++++++++++++++++++++++++++++
 mappers/mapper_005_0.h |  27 +++++
 3 files changed, 342 insertions(+), 2 deletions(-)
 create mode 100644 mappers/mapper_005_0.c
 create mode 100644 mappers/mapper_005_0.h

(limited to 'mappers')

diff --git a/mappers/mapper_004_0.c b/mappers/mapper_004_0.c
index 34970d6..2104c3d 100644
--- a/mappers/mapper_004_0.c
+++ b/mappers/mapper_004_0.c
@@ -159,12 +159,12 @@ static void mapper_004_0_ciram_write(struct nes_state *state, uint32_t addr, uin
 	}
 }
 
-static void mapper_004_0_tick(struct nes_state *state) {
+static void mapper_004_0_tick(struct nes_state *state, uint16_t scanline, uint16_t dot) {
 	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(dot == 260 && scanline < 240) {
 		if(mapper->irq_counter == 0 || mapper->irq_reload) {
 			mapper->irq_counter = mapper->irq_latch;
 			if(mapper->irq_reload) {
diff --git a/mappers/mapper_005_0.c b/mappers/mapper_005_0.c
new file mode 100644
index 0000000..b76311c
--- /dev/null
+++ b/mappers/mapper_005_0.c
@@ -0,0 +1,313 @@
+
+
+__attribute__((always_inline))
+static inline void mapper_005_0_update_prg_banks(struct nes_state *state) {
+	struct mapper_005_0 *mapper = &state->mapper_data.m005_0;
+
+	uint32_t prg_size = state->ines.prg_size;
+
+	// $6000-$7fff: 8kb ram bank from $5113
+	mapper->prg_banks[0] = state->sram + ((mapper->prg_bank_regs[0] & 0x07) * 0x2000);
+
+	switch(mapper->prg_mode) {
+		case 0: {
+			// 32kb mode: $5117 controls all of $8000-$ffff
+			uint32_t bank = (mapper->prg_bank_regs[4] & 0x7c) >> 2;
+			uint32_t offset = (bank * 0x8000) % prg_size;
+			mapper->prg_banks[1] = state->prg_rom + offset;
+			mapper->prg_banks[2] = state->prg_rom + offset + 0x2000;
+			mapper->prg_banks[3] = state->prg_rom + offset + 0x4000;
+			mapper->prg_banks[4] = state->prg_rom + offset + 0x6000;
+		} break;
+
+		case 1: {
+			// 16kb mode: $5115 controls $8000-$bfff, $5117 controls $c000-$ffff
+			uint32_t bank_low = (mapper->prg_bank_regs[2] & 0x7e) >> 1;
+			uint32_t bank_high = (mapper->prg_bank_regs[4] & 0x7e) >> 1;
+			uint32_t offset_low = (bank_low * 0x4000) % prg_size;
+			uint32_t offset_high = (bank_high * 0x4000) % prg_size;
+			mapper->prg_banks[1] = state->prg_rom + offset_low;
+			mapper->prg_banks[2] = state->prg_rom + offset_low + 0x2000;
+			mapper->prg_banks[3] = state->prg_rom + offset_high;
+			mapper->prg_banks[4] = state->prg_rom + offset_high + 0x2000;
+		} break;
+
+		case 2: {
+			// 16kb+8kb+8kb: $5115 controls $8000-$bfff, $5116 controls $c000-$dfff, $5117 controls $e000-$ffff
+			uint32_t bank_0 = (mapper->prg_bank_regs[2] & 0x7e) >> 1;
+			uint32_t bank_1 = mapper->prg_bank_regs[3] & 0x7f;
+			uint32_t bank_2 = mapper->prg_bank_regs[4] & 0x7f;
+			mapper->prg_banks[1] = state->prg_rom + ((bank_0 * 0x4000) % prg_size);
+			mapper->prg_banks[2] = state->prg_rom + ((bank_0 * 0x4000 + 0x2000) % prg_size);
+			mapper->prg_banks[3] = state->prg_rom + ((bank_1 * 0x2000) % prg_size);
+			mapper->prg_banks[4] = state->prg_rom + ((bank_2 * 0x2000) % prg_size);
+		} break;
+
+		case 3: {
+			// 8kb mode: each register controls its own 8kb bank
+			for(int i = 0; i < 4; i++) {
+				uint32_t bank = mapper->prg_bank_regs[i + 1] & 0x7f;
+				mapper->prg_banks[i + 1] = state->prg_rom + ((bank * 0x2000) % prg_size);
+			}
+		} break;
+	}
+}
+
+__attribute__((always_inline))
+static inline void mapper_005_0_update_chr_banks(struct nes_state *state) {
+	struct mapper_005_0 *mapper = &state->mapper_data.m005_0;
+
+	if(!state->ines.chr_size) {
+		return;
+	}
+
+	uint32_t chr_size = state->ines.chr_size;
+
+	// background CHR banks ($5120-$5127)
+	switch(mapper->chr_mode) {
+		case 0: {
+			// 8kb mode: use last register
+			uint32_t bank = mapper->chr_bank_regs[7] | (mapper->chr_upper << 8);
+			uint32_t offset = (bank * 0x2000) % chr_size;
+			for(int i = 0; i < 8; i++) {
+				mapper->chr_banks_bg[i] = state->chr_rom + offset + (i * 0x400);
+			}
+		} break;
+
+		case 1: {
+			// 4kb mode: registers $5123 and $5127
+			uint32_t bank_low = mapper->chr_bank_regs[3] | (mapper->chr_upper << 8);
+			uint32_t bank_high = mapper->chr_bank_regs[7] | (mapper->chr_upper << 8);
+			for(int i = 0; i < 4; i++) {
+				mapper->chr_banks_bg[i] = state->chr_rom + ((bank_low * 0x1000) % chr_size) + (i * 0x400);
+				mapper->chr_banks_bg[i + 4] = state->chr_rom + ((bank_high * 0x1000) % chr_size) + (i * 0x400);
+			}
+		} break;
+
+		case 2: {
+			// 2kb mode: registers $5121, $5123, $5125, $5127
+			for(int i = 0; i < 4; i++) {
+				uint32_t bank = mapper->chr_bank_regs[i * 2 + 1] | (mapper->chr_upper << 8);
+				uint32_t offset = (bank * 0x800) % chr_size;
+				mapper->chr_banks_bg[i * 2] = state->chr_rom + offset;
+				mapper->chr_banks_bg[i * 2 + 1] = state->chr_rom + offset + 0x400;
+			}
+		} break;
+
+		case 3: {
+			// 1kb mode: all registers
+			for(int i = 0; i < 8; i++) {
+				uint32_t bank = mapper->chr_bank_regs[i] | (mapper->chr_upper << 8);
+				mapper->chr_banks_bg[i] = state->chr_rom + ((bank * 0x400) % chr_size);
+			}
+		} break;
+	}
+
+	// sprite CHR banks ($5128-$512B) - 4 registers control 8 1kb banks (each is 2kb)
+	for(int i = 0; i < 4; i++) {
+		uint32_t bank = mapper->chr_bank_regs[8 + i] | (mapper->chr_upper << 8);
+		uint32_t offset = (bank * 0x800) % chr_size;
+		mapper->chr_banks_sp[i * 2] = state->chr_rom + offset;
+		mapper->chr_banks_sp[i * 2 + 1] = state->chr_rom + offset + 0x400;
+	}
+}
+
+static uint8_t mapper_005_0_prg_rom_read(struct nes_state *state, uint32_t addr) {
+	struct mapper_005_0 *mapper = &state->mapper_data.m005_0;
+
+	uint32_t bank = (addr >> 13) & 3;
+	return mapper->prg_banks[bank + 1][addr & 0x1fff];
+}
+
+static uint8_t mapper_005_0_prg_ram_read(struct nes_state *state, uint32_t addr) {
+	struct mapper_005_0 *mapper = &state->mapper_data.m005_0;
+
+	// handle MMC5 registers at $5000-$5fff
+	if(addr >= 0x5c00 && addr <= 0x5fff) {
+		return mapper->exram[addr & 0x3ff];
+	} else if(addr == 0x5204) {
+		uint8_t status = mapper->irq_status;
+		mapper->irq_status &= ~0x80;
+		state->cpu.irq_pending = 0;
+		return status;
+	} else if(addr >= 0x5000 && addr < 0x6000) {
+		return 0; // other MMC5 registers return open bus
+	}
+
+	return mapper->prg_banks[0][addr & 0x1fff];
+}
+
+static void mapper_005_0_prg_ram_write(struct nes_state *state, uint32_t addr, uint8_t value) {
+	struct mapper_005_0 *mapper = &state->mapper_data.m005_0;
+
+	// handle MMC5 registers at $5000-$5fff
+	if(addr >= 0x5c00 && addr <= 0x5fff) {
+		mapper->exram[addr & 0x3ff] = value;
+		return;
+	} else if(addr >= 0x5000 && addr < 0x6000) {
+		// MMC5 control registers
+		switch(addr) {
+			case 0x5100:
+				mapper->prg_mode = value & 0x03;
+				mapper_005_0_update_prg_banks(state);
+				break;
+
+			case 0x5101:
+				mapper->chr_mode = value & 0x03;
+				mapper_005_0_update_chr_banks(state);
+				break;
+
+			case 0x5104:
+				mapper->exram_mode = value & 0x03;
+				break;
+
+			case 0x5105:
+				mapper->nametable_mapping = value;
+				break;
+
+			case 0x5106:
+				mapper->fill_tile = value;
+				break;
+
+			case 0x5107:
+				mapper->fill_attr = value & 0x03;
+				break;
+
+			case 0x5113:
+			case 0x5114:
+			case 0x5115:
+			case 0x5116:
+			case 0x5117: {
+				uint32_t reg = addr - 0x5113;
+				mapper->prg_bank_regs[reg] = value;
+				mapper_005_0_update_prg_banks(state);
+			} break;
+
+			default:
+				if(addr >= 0x5120 && addr <= 0x512b) {
+					uint32_t reg = addr - 0x5120;
+					mapper->chr_bank_regs[reg] = value;
+					mapper_005_0_update_chr_banks(state);
+				} else if(addr == 0x5130) {
+					mapper->chr_upper = value & 0x03;
+					mapper_005_0_update_chr_banks(state);
+				} else if(addr == 0x5203) {
+					mapper->irq_scanline = value;
+				} else if(addr == 0x5204) {
+					mapper->irq_pending = value & 0x80;
+				}
+				break;
+		}
+		return;
+	}
+
+	mapper->prg_banks[0][addr & 0x1fff] = value;
+}
+
+static uint8_t mapper_005_0_chr_read(struct nes_state *state, uint32_t addr) {
+	struct mapper_005_0 *mapper = &state->mapper_data.m005_0;
+
+	if(state->ines.chr_size == 0) {
+		return state->chr_ram[addr];
+	}
+
+	uint32_t bank = (addr >> 10) & 7;
+	return mapper->chr_banks_bg[bank][addr & 0x3ff];
+}
+
+static void mapper_005_0_chr_write(struct nes_state *state, uint32_t addr, uint8_t value) {
+	state->chr_ram[addr] = value;
+}
+
+static uint8_t mapper_005_0_ciram_read(struct nes_state *state, uint32_t addr) {
+	struct mapper_005_0 *mapper = &state->mapper_data.m005_0;
+
+	// determine which nametable (0-3) based on address
+	uint32_t nt = (addr >> 10) & 0x03;
+	uint32_t mapping = (mapper->nametable_mapping >> (nt * 2)) & 0x03;
+
+	switch(mapping) {
+		case 0: return state->ciram[addr & 0x3ff];
+		case 1: return state->ciram[0x400 | (addr & 0x3ff)];
+		case 2: return mapper->exram[addr & 0x3ff];
+		case 3: return mapper->fill_tile;
+	}
+	return 0;
+}
+
+static void mapper_005_0_ciram_write(struct nes_state *state, uint32_t addr, uint8_t value) {
+	struct mapper_005_0 *mapper = &state->mapper_data.m005_0;
+
+	uint32_t nt = (addr >> 10) & 0x03;
+	uint32_t mapping = (mapper->nametable_mapping >> (nt * 2)) & 0x03;
+
+	switch(mapping) {
+		case 0: state->ciram[addr & 0x3ff] = value; break;
+		case 1: state->ciram[0x400 | (addr & 0x3ff)] = value; break;
+		case 2:
+			if(mapper->exram_mode < 2) {
+				mapper->exram[addr & 0x3ff] = value;
+			}
+			break;
+	}
+}
+
+static void mapper_005_0_tick(struct nes_state *state, uint16_t scanline, uint16_t dot) {
+	struct mapper_005_0 *mapper = &state->mapper_data.m005_0;
+
+	// simplified scanline IRQ: trigger at start of target scanline
+	if(dot == 0 && scanline < 240) {
+		mapper->in_frame = 1;
+
+		if(scanline == mapper->irq_scanline) {
+			if(mapper->irq_pending) {
+				state->cpu.irq_pending = 1;
+				mapper->irq_status |= 0x80;
+			}
+		}
+	}
+
+	if(scanline == 240 && dot == 0) {
+		mapper->in_frame = 0;
+	}
+}
+
+static void mapper_005_0_init(struct nes_state *state) {
+	struct mapper_005_0 *mapper = &state->mapper_data.m005_0;
+
+	memset(mapper, 0, sizeof(struct mapper_005_0));
+	// default to mode 3 (8kb prg banks) and mode 3 (1kb chr banks)
+	mapper->prg_mode = 3;
+	mapper->chr_mode = 3;
+
+	// default nametable mapping: vertical mirroring
+	mapper->nametable_mapping = 0x44;
+
+	// initialize prg banks to last 4 banks (mode 3 default)
+	uint32_t prg_bank_count = state->ines.prg_size / 0x2000;
+	mapper->prg_bank_regs[1] = (prg_bank_count - 4) & 0x7f;
+	mapper->prg_bank_regs[2] = (prg_bank_count - 3) & 0x7f;
+	mapper->prg_bank_regs[3] = (prg_bank_count - 2) & 0x7f;
+	mapper->prg_bank_regs[4] = (prg_bank_count - 1) & 0x7f;
+
+	mapper_005_0_update_prg_banks(state);
+
+	if(state->ines.chr_size) {
+		mapper_005_0_update_chr_banks(state);
+	} else {
+		for(int i = 0; i < 8; i++) {
+			mapper->chr_banks_bg[i] = state->chr_ram + (i * 0x400);
+			mapper->chr_banks_sp[i] = state->chr_ram + (i * 0x400);
+		}
+	}
+
+	state->mapper_function.prg_rom_read = mapper_005_0_prg_rom_read;
+	state->mapper_function.prg_rom_write = mapper_default_prg_rom_write;
+	state->mapper_function.prg_ram_read = mapper_005_0_prg_ram_read;
+	state->mapper_function.prg_ram_write = mapper_005_0_prg_ram_write;
+	state->mapper_function.chr_read = mapper_005_0_chr_read;
+	state->mapper_function.chr_write = mapper_005_0_chr_write;
+	state->mapper_function.ciram_read = mapper_005_0_ciram_read;
+	state->mapper_function.ciram_write = mapper_005_0_ciram_write;
+	state->mapper_function.tick = mapper_005_0_tick;
+}
diff --git a/mappers/mapper_005_0.h b/mappers/mapper_005_0.h
new file mode 100644
index 0000000..f9b9851
--- /dev/null
+++ b/mappers/mapper_005_0.h
@@ -0,0 +1,27 @@
+
+
+struct mapper_005_0 {
+	uint8_t *prg_banks[5];		// banks at $6000, $8000, $a000, $c000, $e000
+	uint8_t *chr_banks_bg[8];	// 1kb banks at $0000-$1fff for background
+	uint8_t *chr_banks_sp[8];	// 1kb banks at $0000-$1fff for sprites
+
+	uint8_t prg_mode;
+	uint8_t chr_mode;
+	uint8_t prg_bank_regs[5];		// $5113-$5117
+	uint8_t chr_bank_regs[12];		// $5120-$512b (0-7=bg, 8-11=sprites)
+	uint8_t chr_upper;				// $5130
+
+	uint8_t nametable_mapping;		// $5105
+	uint8_t fill_tile;				// $5106
+	uint8_t fill_attr;				// $5107
+
+	uint8_t exram_mode;
+	uint8_t exram[1024];
+
+	uint8_t irq_scanline;			// $5203
+	uint8_t irq_status;				// $5204
+	uint8_t irq_pending;
+
+	uint8_t in_frame;
+	uint16_t scanline_counter;
+} __attribute__((packed, aligned(64)));
-- 
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