From e8ff6bf2ab9982c5e5ab8d8f4e7adcc5207d079d Mon Sep 17 00:00:00 2001
From: Peter Fors <peter.fors@mindkiller.com>
Date: Sat, 29 Mar 2025 19:57:00 +0100
Subject: first mknes commit

---
 mknes.h | 146 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 146 insertions(+)
 create mode 100644 mknes.h

(limited to 'mknes.h')

diff --git a/mknes.h b/mknes.h
new file mode 100644
index 0000000..1f82ae1
--- /dev/null
+++ b/mknes.h
@@ -0,0 +1,146 @@
+
+
+
+// PPUSTATUS ($2002) flags
+#define PPU_STATUS_VBLANK			0x80
+#define PPU_STATUS_SPRITE0_HIT	0x40
+#define PPU_STATUS_OVERFLOW		0x20
+
+// PPUMASK ($2001) flags
+#define PPU_MASK_SHOW_BG			0x08
+#define PPU_MASK_SHOW_SPRITES		0x10
+
+// PPUCTRL ($2000) flags
+#define PPU_CTRL_NMI_ENABLE		0x80
+#define PPU_CTRL_MASTER_SLAVE		0x40
+#define PPU_CTRL_SPRITE_HEIGHT	0x20
+#define PPU_CTRL_BG_TABLE			0x10
+#define PPU_CTRL_SPRITE_TABLE		0x08
+#define PPU_CTRL_INCREMENT			0x04
+#define PPU_CTRL_NT_SELECT_Y		0x02
+#define PPU_CTRL_NT_SELECT_X		0x01
+
+
+struct nes_state;
+
+struct ppu_state {
+	uint8_t pixels[240*256];
+	uint8_t sprite_pixels[256];	// Sprite pixel color indexes (BG priority resolved)
+	uint8_t sprite_zero_flags[256];	// 1 if pixel came from sprite #0 and is nonzero
+	// Sprite memory
+	uint8_t oam[256];
+	uint8_t sec_oam[32];
+
+	uint8_t oam_addr;
+	uint8_t read_buffer;
+
+	uint32_t scanline;		// 0–261
+	uint32_t dot;			// 0–340
+
+	// Scroll state
+	uint32_t coarse_x_offs;
+	uint32_t coarse_y_offs;
+	uint32_t fine_x;
+	uint32_t fine_y;
+	uint32_t nt_base_x;
+	uint32_t nt_base_y;
+
+	// Latch state for $2005/$2006
+	uint8_t write_toggle;
+	uint32_t temp_coarse_x_offs;
+	uint32_t temp_coarse_y_offs;
+	uint32_t temp_fine_x;
+	uint32_t temp_fine_y;
+	uint32_t temp_nt_base_x;
+	uint32_t temp_nt_base_y;
+
+	// Background shift registers
+	uint32_t bg_tile_lsb;
+	uint32_t bg_tile_msb;
+	uint32_t bg_attr_lsb;
+	uint32_t bg_attr_msb;
+
+	// Tile fetch latches
+	uint8_t nt_byte;
+	uint8_t attr_byte;
+	uint8_t tile_lsb;
+	uint8_t tile_msb;
+
+	// Control and status
+	uint8_t ctrl;		// $2000
+	uint8_t mask;		// $2001
+	uint8_t status;		// $2002
+
+	// Flags
+	uint8_t frame_even;
+	uint8_t nmi_occurred;
+	uint8_t nmi_output;
+
+};
+
+
+struct cpu_state {
+	uint32_t pc;	// Program Counter
+	uint8_t sp;		// Stack Pointer
+	uint8_t a;		// Accumulator
+	uint8_t x;		// X Register
+	uint8_t y;		// Y Register
+	uint8_t p;		// Processor Status Flags (this can be expanded with separate flags if needed)
+	uint8_t n;		// Negative Flag
+	uint8_t v;		// Overflow Flag
+	// uint8_t b;		// Break Flag (Set by BRK instruction)
+	uint8_t d;		// Decimal Flag
+	uint8_t i;		// Interrupt Disable Flag
+	uint8_t z;		// Zero Flag
+	uint8_t c;		// Carry Flag
+// --
+	uint8_t die;	// KIL instruction found!
+};
+
+
+struct ines_state {
+	uint16_t mapper;
+	uint8_t mirroring;	// 0 = H, 1 = V, 2 = 4-screen
+	uint32_t prg_size;
+	uint32_t chr_size;
+};
+
+struct mapper {
+	void (*init)(struct nes_state *state);
+	uint8_t (*read)(struct nes_state *state, uint16_t addr);
+	void (*write)(struct nes_state *state, uint16_t addr, uint8_t value);
+	void (*tick)(struct nes_state *state);
+};
+
+union mapper_data {
+	// struct nrom_mapper nrom;
+	// struct mmc1_mapper mmc1;
+	// ... others
+};
+
+struct nes_state {
+	struct ines_state ines;
+	struct cpu_state cpu;
+	struct ppu_state ppu;
+	struct mapper mapper;
+	union mapper_data map;
+	size_t cycle;
+	uint8_t ram[2048];
+	uint8_t rom[4 * 1024 * 1024];
+	uint8_t chrrom[4 * 1024 * 1024];
+	uint8_t ciram[2048];
+	uint8_t palette[0x20];
+	uint8_t irq_pending;
+	uint8_t nmi_pending;
+};
+
+static const uint32_t nes_palette_argb[64] = {
+	0xff757575, 0xff8f1b27, 0xffab0000, 0xff9f0047, 0xff77008f, 0xff1300ab, 0xff0000a7, 0xff000b7f,
+	0xff002f43, 0xff004700, 0xff005100, 0xff173f00, 0xff5f3f1b, 0xff000000, 0xff000000, 0xff000000,
+	0xffbcbcbc, 0xffef7300, 0xffef3b23, 0xfff30083, 0xffbf00bf, 0xff5b00e7, 0xff002bdb, 0xff0f4fcb,
+	0xff00738b, 0xff009700, 0xff00ab00, 0xff3b9300, 0xff8b8300, 0xff000000, 0xff000000, 0xff000000,
+	0xffffffff, 0xffffbf3f, 0xffff975f, 0xfffd8ba7, 0xffff7bff, 0xffb777ff, 0xff6377ff, 0xff3b9bff,
+	0xff3fbff3, 0xff13d383, 0xff4bdf4f, 0xff98f858, 0xffdbeb00, 0xff000000, 0xff000000, 0xff000000,
+	0xffffffff, 0xffffe7ab, 0xffffd7c7, 0xffffcbd7, 0xffffc7ff, 0xffdbc7ff, 0xffb3bfff, 0xffabdbff,
+	0xffa3e7ff, 0xff83f7c7, 0xffb3ffbf, 0xffcfffb3, 0xfff3ff9f, 0xff000000, 0xff000000, 0xff000000
+};
-- 
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