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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 tile_size = unsigned{ 8 };
// Writes to some registers are ignored until this clock cycle.
static constexpr auto boot_up_cycles = cycle_count::from_ppu(29658);
enum class color : std::uint8_t
{
};
struct color_index
{
auto get_color() const -> unsigned { return (value & 0b00000011) >> 0; }
auto get_palette() const -> unsigned { return (value & 0b00001100) >> 2; }
auto get_foreground() const -> bool { return value & 0b00010000; }
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_foreground(bool const v) -> void { value = (value & ~0b00010000) | (v ? 0b00010000 : 0); }
std::uint8_t value{};
color_index() = default;
explicit color_index(std::uint8_t const value)
: value{ value }
{
}
};
struct sprite
{
// Tile index and pattern table for large sprites
auto get_pattern_table() const -> unsigned { return (tile_index & 0b00000001) >> 0; }
auto get_top_tile() const -> unsigned { return (tile_index & 0b11111110) >> 1; }
auto set_pattern_table(unsigned const v) -> void { tile_index = (tile_index & ~0b00000001) | ((v << 0) & 0b00000001); }
auto set_top_tile(unsigned const v) -> void { tile_index = (tile_index & ~0b11111110) | ((v << 1) & 0b11111110); }
// Attributes
auto get_palette() const -> unsigned { return (attributes & 0b00000011) >> 0; }
auto get_behind_background() const -> bool { return attributes & 0b00100000; }
auto get_flip_horizontal() const -> bool { return attributes & 0b01000000; }
auto get_flip_vertical() const -> bool { return attributes & 0b10000000; }
auto set_palette(unsigned const v) -> void { attributes = (attributes & ~0b00000011) | ((v << 0) & 0b00000011); }
auto set_behind_background(bool const v) -> void { attributes = (attributes & ~0b00100000) | (v ? 0b00100000 : 0); }
auto set_flip_horizontal(bool const v) -> void { attributes = (attributes & ~0b01000000) | (v ? 0b01000000 : 0); }
auto set_flip_vertical(bool const v) -> void { attributes = (attributes & ~0b10000000) | (v ? 0b10000000 : 0); }
std::uint8_t y{};
std::uint8_t tile_index{};
std::uint8_t attributes{};
std::uint8_t x{};
explicit sprite() = default;
explicit sprite(std::uint8_t const y, std::uint8_t const tile_index, std::uint8_t const attributes, std::uint8_t const x)
: y{ y }
, tile_index{ tile_index }
, attributes{ attributes }
, x{ x }
{
}
};
struct tile_row
{
color_index colors[tile_size]{};
};
struct evaluated_sprite
{
tile_row pattern;
std::uint8_t x{ 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); }
// Set the remaining (unused) bits based on the given value.
auto set_remaining(std::uint8_t const v) -> void { value = (value & ~0b00011111) | (v & 0b00011111); }
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
struct
{
// Scroll position
auto get_coarse_x() const -> unsigned { return (value & 0b0000000000011111) >> 0; }
auto get_coarse_y() const -> unsigned { return (value & 0b0000001111100000) >> 5; }
auto get_name_table() const -> unsigned { return (value & 0b0000110000000000) >> 10; }
auto get_horizontal_name_table() const -> unsigned { return (value & 0b0000010000000000) >> 10; }
auto get_vertical_name_table() const -> unsigned { return (value & 0b0000100000000000) >> 11; }
auto get_tile_address() const -> unsigned { return (value & 0b0000111111111111) >> 0; }
auto get_fine_y() const -> unsigned { return (value & 0b0111000000000000) >> 12; }
auto set_coarse_x(unsigned const v) -> void { value = (value & ~0b0000000000011111) | ((v << 0) & 0b0000000000011111); }
auto set_coarse_y(unsigned const v) -> void { value = (value & ~0b0000001111100000) | ((v << 5) & 0b0000001111100000); }
auto set_name_table(unsigned const v) -> void { value = (value & ~0b0000110000000000) | ((v << 10) & 0b0000110000000000); }
auto set_horizontal_name_table(unsigned const v) -> void { value = (value & ~0b0000010000000000) | ((v << 10) & 0b0000010000000000); }
auto set_vertical_name_table(unsigned const v) -> void { value = (value & ~0b0000100000000000) | ((v << 11) & 0b0000100000000000); }
auto set_tile_address(unsigned const v) -> void { value = (value & ~0b0000111111111111) | ((v << 0) & 0b0000111111111111); }
auto set_fine_y(unsigned const v) -> void { value = (value & ~0b0111000000000000) | ((v << 12) & 0b0111000000000000); }
// Address
auto get_address_low() const -> unsigned { return (value & 0b0000000011111111) >> 0; }
auto get_address_high() const -> unsigned { return (value & 0b0111111100000000) >> 8; }
auto set_address_low(unsigned const v) -> void { value = (value & ~0b0000000011111111) | ((v << 0) & 0b0000000011111111); }
auto set_address_high(unsigned const v) -> void { value = (value & ~0b0111111100000000) | ((v << 8) & 0b0111111100000000); }
std::uint16_t value{};
} v{}, t{}; // Current and temporary VRAM address and scroll position (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 };
tile_row current_background_{};
tile_row next_background_{};
struct
{
std::uint8_t tile{ 0 };
std::uint8_t palette{ 0 };
std::uint8_t bitplane_0{ 0 };
std::uint8_t bitplane_1{ 0 };
} fetch_cycle_{}; // Data populated during the fetch cycle.
evaluated_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 evaluate_sprites() -> void;
auto fetch_sprite_pattern(sprite, unsigned row) -> tile_row;
// Helpers
auto increment_vram() -> void;
auto increment_x() -> void;
auto increment_y() -> void;
auto copy_x() -> void;
auto copy_y() -> void;
auto get_sprite_height() const -> unsigned;
auto get_sprite(unsigned) const -> sprite;
auto get_tile_bitplane(unsigned pattern_table, unsigned tile, unsigned row, unsigned bitplane) -> std::uint8_t;
auto get_tile_row(unsigned palette, std::uint8_t bitplane_0, std::uint8_t bitplane_1) const -> tile_row;
auto ref_color(color_index) -> color&;
auto resolve_color(color) const -> rgb;
};
} // namespace nes
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