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#pragma once
#include "nes/util/cycle_count.hh"
namespace nes
{
class address;
class cpu;
class mapper;
class display;
class rgb;
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 vram_increment
{
add_1_across = 0,
add_32_down = 1,
};
enum class sprite_size
{
_8x8 = 0,
_8x16 = 1,
};
enum class role
{
background = 0,
sprite = 1,
};
enum class color : std::uint8_t
{
};
union color_index
{
struct __attribute__((packed))
{
unsigned color : 2;
unsigned palette : 2;
role role : 1;
};
unsigned value;
explicit color_index(unsigned 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.
union
{
struct __attribute__((packed))
{
bool : 1;
bool : 1;
bool : 1;
bool : 1;
bool : 1;
bool sprite_overflow : 1;
bool sprite_zero_hit : 1;
bool vblank : 1;
};
std::uint8_t value{ 0b00000000 };
} status_{};
union
{
struct __attribute__((packed))
{
std::uint8_t base_name_table : 2; // Base nametable address.
vram_increment vram_increment : 1; // VRAM increment per CPU read/write of PPUDATA.
std::uint8_t sprite_pattern_table : 1; // Sprite pattern table address for 8x8 sprites.
std::uint8_t background_pattern_table : 1; // Background pattern table address.
sprite_size sprite_size : 1; // Sprite size.
bool enable_ext_pin : 1; // PPU master/slave select.
bool vblank_nmi : 1; // Enable/disable Vblank NMI
};
std::uint8_t value{ 0b00000000 };
} control_{};
union
{
struct __attribute__((packed))
{
bool grayscale : 1; // Enable/disable grayscale.
bool show_background_start : 1; // Show background in leftmost 8 pixels of screen.
bool show_sprites_start : 1; // Show sprites in leftmost 8 pixels of screen.
bool enable_background : 1; // Enable background rendering.
bool enable_sprites : 1; // Enable sprite rendering.
bool emphasize_red : 1; // Emphasize red.
bool emphasize_green : 1; // Emphasize green.
bool emphasize_blue : 1; // Emphasize blue.
};
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_.
unsigned nmi_delay_{ 0 }; // Delay until an NMI is requested if conditions still met.
bool nmi_requested_{ false };
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 step_to(cycle_count) -> 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 step() -> void;
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 nmi_change() -> void;
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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