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#pragma once
#include "nes/util/cycle-count.hh"
namespace nes
{
class address;
class cpu;
class mapper;
class display;
class rgb;
struct snapshot;
class ppu
{
static constexpr auto vram_size = std::size_t{ 0x800 };
static constexpr auto oam_size = std::size_t{ 0x100 };
static constexpr auto palette_buffer_size = std::size_t{ 0x20 };
static constexpr auto status_mask = std::uint8_t{ 0b11100000 };
// Writes to some registers are ignored until this clock cycle.
static constexpr auto boot_up_cycles = cycle_count::from_ppu(29658);
enum class role : unsigned
{
background = 0,
sprite = 1,
};
enum class color : std::uint8_t
{
};
struct color_index
{
auto get_color() const -> unsigned { return (value & 0b00000011u) >> 0; }
auto get_palette() const -> unsigned { return (value & 0b00001100u) >> 2; }
auto get_role() const -> role { return role{ (value & 0b00010000u) >> 4 }; }
auto set_color(unsigned const v) -> void { value = (value & ~0b00000011) | ((v << 0) & 0b00000011); }
auto set_palette(unsigned const v) -> void { value = (value & ~0b00001100) | ((v << 2) & 0b00001100); }
auto set_role(unsigned const v) -> void { value = (value & ~0b00010000) | ((v << 4) & 0b00010000); }
auto set_role(role const v) -> void { set_role(static_cast<unsigned>(v)); }
std::uint8_t value{};
explicit color_index(std::uint8_t const value)
: value{ value }
{
}
};
struct sprite
{
std::uint32_t pattern{ 0 };
std::uint8_t position{ 0 };
bool is_in_front{ false };
bool is_sprite_zero{ false };
};
cycle_count current_cycles_;
cpu& cpu_;
mapper& mapper_;
display& display_;
std::uint8_t vram_[vram_size]{};
std::uint8_t oam_[oam_size]{};
color palette_buffer_[palette_buffer_size]
{
color{ 0x09 }, color{ 0x01 }, color{ 0x00 }, color{ 0x01 },
color{ 0x00 }, color{ 0x02 }, color{ 0x02 }, color{ 0x0D },
color{ 0x08 }, color{ 0x10 }, color{ 0x08 }, color{ 0x24 },
color{ 0x00 }, color{ 0x00 }, color{ 0x04 }, color{ 0x2C },
color{ 0x09 }, color{ 0x01 }, color{ 0x34 }, color{ 0x03 },
color{ 0x00 }, color{ 0x04 }, color{ 0x00 }, color{ 0x14 },
color{ 0x08 }, color{ 0x3A }, color{ 0x00 }, color{ 0x02 },
color{ 0x00 }, color{ 0x20 }, color{ 0x2C }, color{ 0x08 },
};
std::uint8_t latch_{}; // The last read/written IO register value, returned when reading write-only registers.
struct
{
auto get_sprite_overflow() const -> bool { return value & 0b00100000; }
auto get_sprite_zero_hit() const -> bool { return value & 0b01000000; }
auto get_vblank() const -> bool { return value & 0b10000000; }
auto set_sprite_overflow(bool const v) -> void { value = (value & ~0b00100000) | (v ? 0b00100000 : 0); }
auto set_sprite_zero_hit(bool const v) -> void { value = (value & ~0b01000000) | (v ? 0b01000000 : 0); }
auto set_vblank(bool const v) -> void { value = (value & ~0b10000000) | (v ? 0b10000000 : 0); }
std::uint8_t value{ 0b00000000 };
} status_{};
struct
{
// Base nametable address.
auto get_base_name_table() const -> unsigned { return (value & 0b00000011u) >> 0; }
// Increment VRAM addresses downward (+ 32) instead of moving to the right (+ 1) on each read/write.
auto get_vram_row_increment() const -> bool { return value & 0b00000100; }
// Sprite pattern table address for 8x8 sprites.
auto get_sprite_pattern_table() const -> unsigned { return (value & 0b00001000u) >> 3; }
// Background pattern table address.
auto get_background_pattern_table() const -> unsigned { return (value & 0b00010000u) >> 4; }
// Whether to use double-height (8x16) instead of 8x8 sprites.
auto get_large_sprites() const -> bool { return value & 0b00100000; }
// PPU master/slave select.
auto get_enable_ext_pin() const -> bool { return value & 0b01000000; }
// Enable/disable vblank NMI.
auto get_vblank_nmi() const -> bool { return value & 0b10000000; }
auto set_base_name_table(unsigned const v) -> void { value = (value & ~0b00000011) | ((v << 0) & 0b00000011); }
auto set_vram_row_increment(bool const v) -> void { value = (value & ~0b00000100) | (v ? 0b00000100 : 0); }
auto set_sprite_pattern_table(unsigned const v) -> void { value = (value & ~0b00001000) | ((v << 3) & 0b00001000); }
auto set_background_pattern_table(unsigned const v) -> void { value = (value & ~0b00010000) | ((v << 4) & 0b00010000); }
auto set_large_sprites(bool const v) -> void { value = (value & ~0b00100000) | (v ? 0b00100000 : 0); }
auto set_enable_ext_pin(bool const v) -> void { value = (value & ~0b01000000) | (v ? 0b01000000 : 0); }
auto set_vblank_nmi(bool const v) -> void { value = (value & ~0b10000000) | (v ? 0b10000000 : 0); }
std::uint8_t value{ 0b00000000 };
} control_{};
struct
{
// Enable/disable grayscale.
auto get_grayscale() const -> bool { return value & 0b00000001; }
// Show background in leftmost 8 pixels of screen.
auto get_show_background_start() const -> bool { return value & 0b00000010; }
// Show sprites in leftmost 8 pixels of screen.
auto get_show_sprites_start() const -> bool { return value & 0b00000100; }
// Enable background rendering.
auto get_enable_background() const -> bool { return value & 0b00001000; }
// Enable sprite rendering.
auto get_enable_sprites() const -> bool { return value & 0b00010000; }
// Emphasize red.
auto get_emphasize_red() const -> bool { return value & 0b00100000; }
// Emphasize green.
auto get_emphasize_green() const -> bool { return value & 0b01000000; }
// Emphasize blue.
auto get_emphasize_blue() const -> bool { return value & 0b10000000; }
auto set_grayscale(bool const v) -> void { value = (value & ~0b00000001) | (v ? 0b00000001 : 0); }
auto set_show_background_start(bool const v) -> void { value = (value & ~0b00000010) | (v ? 0b00000010 : 0); }
auto set_show_sprites_start(bool const v) -> void { value = (value & ~0b00000100) | (v ? 0b00000100 : 0); }
auto set_enable_background(bool const v) -> void { value = (value & ~0b00001000) | (v ? 0b00001000 : 0); }
auto set_enable_sprites(bool const v) -> void { value = (value & ~0b00010000) | (v ? 0b00010000 : 0); }
auto set_emphasize_red(bool const v) -> void { value = (value & ~0b00100000) | (v ? 0b00100000 : 0); }
auto set_emphasize_green(bool const v) -> void { value = (value & ~0b01000000) | (v ? 0b01000000 : 0); }
auto set_emphasize_blue(bool const v) -> void { value = (value & ~0b10000000) | (v ? 0b10000000 : 0); }
std::uint8_t value{ 0b00000000 };
} mask_{};
struct
{
// See https://www.nesdev.org/wiki/PPU_scrolling#PPU_internal_registers
std::uint16_t v{}; // Current VRAM address (15 bits)
std::uint16_t t{}; // Temporary VRAM address (15 bits)
std::uint8_t x{}; // Fine X scroll (3 bits)
bool w{}; // Second write toggle (1 bit)
} internal_{};
std::uint8_t oamaddr_{}; // Address accessed by IO registers
std::uint8_t ppudata_read_buffer_{}; // Delays PPUDATA reads by one.
unsigned scanline_{ 240 };
unsigned scanline_cycle_{ 340 };
bool even_frame_{ true };
std::uint64_t tile_data_{ 0 }; // Data for the current tile (higher 32 bits) and the next tile (lower 32 bits).
std::uint8_t name_table_byte_{ 0 };
std::uint8_t attribute_table_byte_{ 0 };
std::uint8_t low_tile_byte_{ 0 };
std::uint8_t high_tile_byte_{ 0 };
sprite sprites_[8]{}; // Evaluated sprites.
unsigned sprite_count_{ 0 }; // Number of evaluated sprites in sprites_.
public:
explicit ppu(cpu&, mapper&, display&);
ppu(ppu const&) = delete;
ppu(ppu&&) = delete;
auto operator=(ppu const&) -> ppu& = delete;
auto operator=(ppu&&) -> ppu& = delete;
auto get_cycles() const -> cycle_count { return current_cycles_; }
auto build_snapshot(snapshot&) -> void;
auto step() -> void;
// Memory access
auto read8(address) -> std::uint8_t;
auto write8(address, std::uint8_t) -> void;
// IO registers
auto read_latch() -> std::uint8_t;
auto read_ppustatus() -> std::uint8_t;
auto read_oamdata() -> std::uint8_t;
auto read_ppudata() -> std::uint8_t;
auto write_latch(std::uint8_t) -> void;
auto write_ppuctrl(std::uint8_t) -> void;
auto write_ppuscroll(std::uint8_t) -> void;
auto write_ppumask(std::uint8_t) -> void;
auto write_ppuaddr(std::uint8_t) -> void;
auto write_ppudata(std::uint8_t) -> void;
auto write_oamaddr(std::uint8_t) -> void;
auto write_oamdata(std::uint8_t) -> void;
auto write_oamdma(std::uint8_t) -> void;
private:
auto render_pixel() -> void;
auto fetch_name_table_byte() -> void;
auto fetch_attribute_table_byte() -> void;
auto fetch_low_tile_byte() -> void;
auto fetch_high_tile_byte() -> void;
auto store_tile_data() -> void;
auto increment_x() -> void;
auto increment_y() -> void;
auto copy_x() -> void;
auto copy_y() -> void;
auto evaluate_sprites() -> void;
auto fetch_sprite_pattern(unsigned i, unsigned row) -> std::uint32_t;
// Helpers
auto sprite_height() -> unsigned;
auto increment_vram() -> void;
auto get_color(color_index) -> color&;
auto resolve_color(color) -> rgb;
};
} // namespace nes
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