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CLK/Components/9918/Implementation/Storage.hpp

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//
//
// Storage.hpp
// Clock Signal
//
// Created by Thomas Harte on 12/02/2023.
// Copyright © 2023 Thomas Harte. All rights reserved.
//
#pragma once
#include "LineBuffer.hpp"
#include "YamahaCommands.hpp"
#include <optional>
#include <vector>
namespace TI::TMS {
/// A container for personality-specific storage; see specific instances below.
template <Personality personality, typename Enable = void> struct Storage {
};
template <> struct Storage<Personality::TMS9918A> {
using AddressT = uint16_t;
void begin_line(ScreenMode, bool) {}
};
struct YamahaFetcher {
public:
/// Describes an _observable_ memory access event. i.e. anything that it is safe
/// (and convenient) to treat as atomic in between external slots.
struct Event {
/// Offset of the _beginning_ of the event. Not completely arbitrarily: this is when
/// external data must be ready by in order to take part in those slots.
uint16_t offset = 1368;
enum class Type: uint8_t {
/// A slot for reading or writing data on behalf of the CPU or the command engine.
External,
//
// Sprites.
//
SpriteY,
SpriteLocation,
SpritePattern,
//
// Backgrounds.
//
Name,
Colour,
Pattern,
} type = Type::External;
uint8_t id = 0;
constexpr Event(Type type, uint8_t id = 0) noexcept :
type(type),
id(id) {}
constexpr Event() noexcept {}
};
// State that tracks fetching position within a line.
const Event *next_event_ = nullptr;
// Sprite collection state.
bool sprites_enabled_ = true;
protected:
/// @return 1 + the number of times within a line that @c GeneratorT produces an event.
template <typename GeneratorT> static constexpr size_t events_size() {
size_t size = 0;
for(int c = 0; c < 1368; c++) {
const auto event_type = GeneratorT::event(c);
size += event_type.has_value();
}
return size + 1;
}
/// @return An array of all events generated by @c GeneratorT in line order.
template <typename GeneratorT, size_t size = events_size<GeneratorT>()>
static constexpr std::array<Event, size> events() {
std::array<Event, size> result{};
size_t index = 0;
for(int c = 0; c < 1368; c++) {
// Specific personality doesn't matter here; both Yamahas use the same internal timing.
const auto event = GeneratorT::event(from_internal<Personality::V9938, Clock::FromStartOfSync>(c));
if(!event) {
continue;
}
result[index] = *event;
result[index].offset = uint16_t(c);
++index;
}
result[index] = Event();
return result;
}
struct StandardGenerators {
static constexpr std::optional<Event> external_every_eight(int index) {
if(index & 7) return std::nullopt;
return Event::Type::External;
}
};
struct RefreshGenerator {
static constexpr std::optional<Event> event(int grauw_index) {
// From 0 to 126: CPU/CMD slots at every cycle divisible by 8.
if(grauw_index < 126) {
return StandardGenerators::external_every_eight(grauw_index - 0);
}
// From 164 to 1234: eight-cycle windows, the first 15 of each 16 being
// CPU/CMD and the final being refresh.
if(grauw_index >= 164 && grauw_index < 1234) {
const int offset = grauw_index - 164;
if(offset & 7) return std::nullopt;
if(((offset >> 3) & 15) == 15) return std::nullopt;
return Event::Type::External;
}
// From 1268 to 1330: CPU/CMD slots at every cycle divisible by 8.
if(grauw_index >= 1268 && grauw_index < 1330) {
return StandardGenerators::external_every_eight(grauw_index - 1268);
}
// A CPU/CMD at 1334.
if(grauw_index == 1334) {
return Event::Type::External;
}
// From 1344 to 1366: CPU/CMD slots every cycle divisible by 8.
if(grauw_index >= 1344 && grauw_index < 1366) {
return StandardGenerators::external_every_eight(grauw_index - 1344);
}
// Otherwise: nothing.
return std::nullopt;
}
};
template <bool include_sprites> struct BitmapGenerator {
static constexpr std::optional<Event> event(int grauw_index) {
if(!include_sprites) {
// Various standard zones of one-every-eight external slots.
if(grauw_index < 124) {
return StandardGenerators::external_every_eight(grauw_index + 2);
}
if(grauw_index > 1266) {
return StandardGenerators::external_every_eight(grauw_index - 1266);
}
} else {
// This records collection points for all data for selected sprites.
// There's only four of them (each site covering two sprites),
// so it's clearer just to be explicit.
//
// There's also a corresponding number of extra external slots to spell out.
switch(grauw_index) {
default: break;
case 1238: return Event(Event::Type::SpriteLocation, 0);
case 1302: return Event(Event::Type::SpriteLocation, 2);
case 2: return Event(Event::Type::SpriteLocation, 4);
case 66: return Event(Event::Type::SpriteLocation, 6);
case 1270: return Event(Event::Type::SpritePattern, 0);
case 1338: return Event(Event::Type::SpritePattern, 2);
case 34: return Event(Event::Type::SpritePattern, 4);
case 98: return Event(Event::Type::SpritePattern, 6);
case 1264: case 1330: case 28: case 92:
return Event::Type::External;
}
}
if(grauw_index >= 162 && grauw_index < 176) {
return StandardGenerators::external_every_eight(grauw_index - 162);
}
// Everywhere else the pattern is:
//
// external or sprite y, external, data block
//
// Subject to caveats:
//
// 1) the first data block is just a dummy fetch with no side effects,
// so this emulator declines to record it; and
// 2) every fourth block, the second external is actually a refresh.
//
if(grauw_index >= 182 && grauw_index < 1238) {
const int offset = grauw_index - 182;
const int block = offset / 32;
const int sub_block = offset & 31;
switch(sub_block) {
default: return std::nullopt;
case 0:
if(include_sprites) {
// Don't include the sprite post-amble (i.e. a spurious read with no side effects).
if(block < 32) {
return Event(Event::Type::SpriteY, uint8_t(block));
}
} else {
return Event::Type::External;
}
case 6:
if((block & 3) != 3) {
return Event::Type::External;
}
break;
case 12:
if(block) {
return Event(Event::Type::Pattern, uint8_t(block - 1));
}
break;
}
}
return std::nullopt;
}
};
struct TextGenerator {
static constexpr std::optional<Event> event(int grauw_index) {
// Capture various one-in-eight zones.
if(grauw_index < 72) {
return StandardGenerators::external_every_eight(grauw_index - 2);
}
if(grauw_index >= 166 && grauw_index < 228) {
return StandardGenerators::external_every_eight(grauw_index - 166);
}
if(grauw_index >= 1206 && grauw_index < 1332) {
return StandardGenerators::external_every_eight(grauw_index - 1206);
}
if(grauw_index == 1336) {
return Event::Type::External;
}
if(grauw_index >= 1346) {
return StandardGenerators::external_every_eight(grauw_index - 1346);
}
// Elsewhere...
if(grauw_index >= 246) {
const int offset = grauw_index - 246;
const int block = offset / 48;
const int sub_block = offset % 48;
switch(sub_block) {
default: break;
case 0: return Event(Event::Type::Name, uint8_t(block));
case 18: return (block & 1) ? Event::Type::External : Event(Event::Type::Colour, uint8_t(block >> 1));
case 24: return Event(Event::Type::Pattern, uint8_t(block));
}
}
return std::nullopt;
}
};
struct CharacterGenerator {
static constexpr std::optional<Event> event(int grauw_index) {
// Grab sprite events.
switch(grauw_index) {
default: break;
case 1242: return Event(Event::Type::SpriteLocation, 0);
case 1306: return Event(Event::Type::SpriteLocation, 1);
case 6: return Event(Event::Type::SpriteLocation, 2);
case 70: return Event(Event::Type::SpriteLocation, 3);
case 1274: return Event(Event::Type::SpritePattern, 0);
case 1342: return Event(Event::Type::SpritePattern, 1);
case 38: return Event(Event::Type::SpritePattern, 2);
case 102: return Event(Event::Type::SpritePattern, 3);
case 1268: case 1334: case 32: case 96: return Event::Type::External;
}
if(grauw_index >= 166 && grauw_index < 180) {
return StandardGenerators::external_every_eight(grauw_index - 166);
}
if(grauw_index >= 182 && grauw_index < 1238) {
const int offset = grauw_index - 182;
const int block = offset / 32;
const int sub_block = offset & 31;
switch(sub_block) {
case 0: if(block > 0) return Event(Event::Type::Name, uint8_t(block - 1));
case 6: if((sub_block & 3) != 3) return Event::Type::External;
case 12: if(block < 32) return Event(Event::Type::SpriteY, uint8_t(block));
case 18: if(block > 0) return Event(Event::Type::Pattern, uint8_t(block - 1));
case 24: if(block > 0) return Event(Event::Type::Colour, uint8_t(block - 1));
}
}
return std::nullopt;
}
};
};
struct YamahaCommandState {
CommandContext command_context_;
ModeDescription mode_description_;
std::unique_ptr<Command> command_ = nullptr;
enum class CommandStep {
None,
CopySourcePixelToStatus,
ReadSourcePixel,
ReadDestinationPixel,
WritePixel,
ReadSourceByte,
WriteByte,
};
CommandStep next_command_step_ = CommandStep::None;
int minimum_command_column_ = 0;
uint8_t command_latch_ = 0;
void update_command_step(int current_column) {
if(!command_) {
next_command_step_ = CommandStep::None;
return;
}
if(command_->done()) {
command_ = nullptr;
next_command_step_ = CommandStep::None;
return;
}
minimum_command_column_ = current_column + command_->cycles;
switch(command_->access) {
case Command::AccessType::ReadPoint:
next_command_step_ = CommandStep::CopySourcePixelToStatus;
break;
case Command::AccessType::CopyPoint:
next_command_step_ = CommandStep::ReadSourcePixel;
break;
case Command::AccessType::PlotPoint:
next_command_step_ = CommandStep::ReadDestinationPixel;
break;
case Command::AccessType::WaitForColourReceipt:
// i.e. nothing to do until a colour is received.
next_command_step_ = CommandStep::None;
break;
case Command::AccessType::CopyByte:
next_command_step_ = CommandStep::ReadSourceByte;
break;
case Command::AccessType::WriteByte:
next_command_step_ = CommandStep::WriteByte;
break;
}
}
};
// Yamaha-specific storage.
template <Personality personality> struct Storage<personality, std::enable_if_t<is_yamaha_vdp(personality)>>: public YamahaFetcher, public YamahaCommandState {
using AddressT = uint32_t;
// The Yamaha's (optional in real hardware) additional 64kb of expansion RAM.
// This is a valid target and source for the command engine, but can't be used as a source for current video data.
std::array<uint8_t, 65536> expansion_ram_;
// Register indirections.
int selected_status_ = 0;
int indirect_register_ = 0;
bool increment_indirect_register_ = false;
// Output horizontal and vertical adjustment, plus the selected vertical offset (i.e. hardware scroll).
int adjustment_[2]{};
uint8_t vertical_offset_ = 0;
// The palette, plus a shadow copy in which colour 0 is not the current palette colour 0,
// but is rather the current global background colour. This simplifies flow when colour 0
// is set as transparent.
std::array<uint32_t, 16> palette_{};
std::array<uint32_t, 16> background_palette_{};
bool solid_background_ = true;
// Transient state for palette setting.
uint8_t new_colour_ = 0;
uint8_t palette_entry_ = 0;
bool palette_write_phase_ = false;
// Recepticle for all five bits of the current screen mode.
uint8_t mode_ = 0;
// Used ephemerally during drawing to compound sprites with the 'CC'
// (compound colour?) bit set.
uint8_t sprite_cache_[8][32]{};
// Text blink colours.
uint8_t blink_text_colour_ = 0;
uint8_t blink_background_colour_ = 0;
// Blink state (which is also affects even/odd page display in applicable modes).
int in_blink_ = 1;
uint8_t blink_periods_ = 0;
uint8_t blink_counter_ = 0;
// Additional things exposed by status registers.
uint8_t colour_status_ = 0;
uint16_t colour_location_ = 0;
uint16_t collision_location_[2]{};
bool line_matches_ = false;
Storage() noexcept {
// Seed to something valid.
next_event_ = refresh_events.data();
}
/// Resets line-ephemeral state for a new line.
void begin_line(ScreenMode mode, bool is_refresh) {
if(is_refresh) {
next_event_ = refresh_events.data();
return;
}
switch(mode) {
case ScreenMode::YamahaText80:
case ScreenMode::Text:
next_event_ = text_events.data();
break;
case ScreenMode::MultiColour:
case ScreenMode::YamahaGraphics1:
case ScreenMode::YamahaGraphics2:
next_event_ = character_events.data();
break;
case ScreenMode::YamahaGraphics3: // TODO: verify; my guess is that G3 is timed like a bitmap mode
// in order to fit the pattern for sprite mode 2. Just a guess.
default:
next_event_ = sprites_enabled_ ? sprites_events.data() : no_sprites_events.data();
break;
}
}
private:
static constexpr auto refresh_events = events<RefreshGenerator>();
static constexpr auto no_sprites_events = events<BitmapGenerator<false>>();
static constexpr auto sprites_events = events<BitmapGenerator<true>>();
static constexpr auto text_events = events<TextGenerator>();
static constexpr auto character_events = events<CharacterGenerator>();
};
// Master System-specific storage.
template <Personality personality> struct Storage<personality, std::enable_if_t<is_sega_vdp(personality)>> {
using AddressT = uint16_t;
// The SMS VDP has a programmer-set colour palette, with a dedicated patch of RAM. But the RAM is only exactly
// fast enough for the pixel clock. So when the programmer writes to it, that causes a one-pixel glitch; there
// isn't the bandwidth for the read both write to occur simultaneously. The following buffer therefore keeps
// track of pending collisions, for visual reproduction.
struct CRAMDot {
LineBufferPointer location;
uint32_t value;
};
std::vector<CRAMDot> upcoming_cram_dots_;
// The Master System's additional colour RAM.
uint32_t colour_ram_[32];
bool cram_is_selected_ = false;
// Programmer-set flags.
bool vertical_scroll_lock_ = false;
bool horizontal_scroll_lock_ = false;
bool hide_left_column_ = false;
bool shift_sprites_8px_left_ = false;
bool mode4_enable_ = false;
uint8_t horizontal_scroll_ = 0;
uint8_t vertical_scroll_ = 0;
// Holds the vertical scroll position for this frame; this is latched
// once and cannot dynamically be changed until the next frame.
uint8_t latched_vertical_scroll_ = 0;
// Various resource addresses with VDP-version-specific modifications
// built in.
AddressT pattern_name_address_;
AddressT sprite_attribute_table_address_;
AddressT sprite_generator_table_address_;
void begin_line(ScreenMode, bool) {}
};
}
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