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CLK/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
2021-04-04 19:12:37 -04:00

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//
// ZXSpectrum.cpp
// Clock Signal
//
// Created by Thomas Harte on 17/03/2021.
// Copyright © 2021 Thomas Harte. All rights reserved.
//
#include "ZXSpectrum.hpp"
#include "Video.hpp"
#define LOG_PREFIX "[Spectrum] "
#include "../../../Activity/Source.hpp"
#include "../../MachineTypes.hpp"
#include "../../../Processors/Z80/Z80.hpp"
#include "../../../Components/AudioToggle/AudioToggle.hpp"
#include "../../../Components/AY38910/AY38910.hpp"
// TODO: possibly there's a better factoring than this, but for now
// just grab the CPC's version of an FDC.
#include "../../AmstradCPC/FDC.hpp"
#include "../../../Outputs/Log.hpp"
#include "../../../Outputs/Speaker/Implementation/CompoundSource.hpp"
#include "../../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
#include "../../../Outputs/Speaker/Implementation/SampleSource.hpp"
#include "../../../Storage/Tape/Tape.hpp"
#include "../../../Storage/Tape/Parsers/Spectrum.hpp"
#include "../../../Analyser/Static/ZXSpectrum/Target.hpp"
#include "../../Utility/MemoryFuzzer.hpp"
#include "../../Utility/Typer.hpp"
#include "../../../ClockReceiver/JustInTime.hpp"
#include "../Keyboard/Keyboard.hpp"
#include <array>
namespace Sinclair {
namespace ZXSpectrum {
using Model = Analyser::Static::ZXSpectrum::Target::Model;
using CharacterMapper = Sinclair::ZX::Keyboard::CharacterMapper;
template<Model model> class ConcreteMachine:
public Activity::Source,
public ClockingHint::Observer,
public Configurable::Device,
public CPU::Z80::BusHandler,
public Machine,
public MachineTypes::AudioProducer,
public MachineTypes::MappedKeyboardMachine,
public MachineTypes::MediaTarget,
public MachineTypes::ScanProducer,
public MachineTypes::TimedMachine,
public Utility::TypeRecipient<CharacterMapper> {
public:
ConcreteMachine(const Analyser::Static::ZXSpectrum::Target &target, const ROMMachine::ROMFetcher &rom_fetcher) :
Utility::TypeRecipient<CharacterMapper>(Sinclair::ZX::Keyboard::Machine::ZXSpectrum),
z80_(*this),
ay_(GI::AY38910::Personality::AY38910, audio_queue_),
audio_toggle_(audio_queue_),
mixer_(ay_, audio_toggle_),
speaker_(mixer_),
keyboard_(Sinclair::ZX::Keyboard::Machine::ZXSpectrum),
keyboard_mapper_(Sinclair::ZX::Keyboard::Machine::ZXSpectrum),
tape_player_(clock_rate() * 2),
fdc_(clock_rate() * 2)
{
set_clock_rate(clock_rate());
speaker_.set_input_rate(float(clock_rate()) / 2.0f);
// With only the +2a and +3 currently supported, the +3 ROM is always
// the one required.
const auto roms =
rom_fetcher({ {"ZXSpectrum", "the +2a/+3 ROM", "plus3.rom", 64 * 1024, 0x96e3c17a} });
if(!roms[0]) throw ROMMachine::Error::MissingROMs;
memcpy(rom_.data(), roms[0]->data(), std::min(rom_.size(), roms[0]->size()));
// Register for sleeping notifications.
tape_player_.set_clocking_hint_observer(this);
// Set up initial memory map.
update_memory_map();
set_video_address();
Memory::Fuzz(ram_);
// Insert media.
insert_media(target.media);
// Possibly depress the enter key.
if(target.should_hold_enter) {
// Hold it for five seconds, more or less.
duration_to_press_enter_ = Cycles(5 * clock_rate());
keyboard_.set_key_state(ZX::Keyboard::KeyEnter, true);
}
}
~ConcreteMachine() {
audio_queue_.flush();
}
static constexpr unsigned int clock_rate() {
// constexpr unsigned int ClockRate = 3'500'000;
constexpr unsigned int Plus3ClockRate = 3'546'875; // See notes below; this is a guess.
// Notes on timing for the +2a and +3:
//
// Standard PAL produces 283.7516 colour cycles per line, each line being 64µs.
// The oft-quoted 3.5469 Mhz would seem to imply 227.0016 clock cycles per line.
// Since those Spectrums actually produce 228 cycles per line, but software like
// Chromatrons seems to assume a fixed phase relationship, I guess that the real
// clock speed is whatever gives:
//
// 228 / [cycles per line] * 283.7516 = [an integer].
//
// i.e. 228 * 283.7516 = [an integer] * [cycles per line], such that cycles per line ~= 227
// ... which would imply that 'an integer' is probably 285, i.e.
//
// 228 / [cycles per line] * 283.7516 = 285
// => 227.00128 = [cycles per line]
// => clock rate = 3.546895 Mhz?
//
// That is... unless I'm mistaken about the PAL colour subcarrier and it's actually 283.75,
// which would give exactly 227 cycles/line and therefore 3.546875 Mhz.
//
// A real TV would be likely to accept either, I guess. But it does seem like
// the Spectrum is a PAL machine with a fixed colour phase relationship. For
// this emulator's world, that's a first!
return Plus3ClockRate;
}
// MARK: - TimedMachine.
void run_for(const Cycles cycles) override {
z80_.run_for(cycles);
// Use this very broad timing base for the automatic enter depression.
// It's not worth polluting the main loop.
if(duration_to_press_enter_ > Cycles(0)) {
if(duration_to_press_enter_ < cycles) {
duration_to_press_enter_ = Cycles(0);
keyboard_.set_key_state(ZX::Keyboard::KeyEnter, false);
} else {
duration_to_press_enter_ -= cycles;
}
}
}
void flush() {
video_.flush();
update_audio();
audio_queue_.perform();
if constexpr (model == Model::Plus3) {
fdc_.flush();
}
}
// MARK: - ScanProducer.
void set_scan_target(Outputs::Display::ScanTarget *scan_target) override {
video_->set_scan_target(scan_target);
}
Outputs::Display::ScanStatus get_scaled_scan_status() const override {
return video_->get_scaled_scan_status();
}
void set_display_type(Outputs::Display::DisplayType display_type) override {
video_->set_display_type(display_type);
}
// MARK: - BusHandler.
forceinline HalfCycles perform_machine_cycle(const CPU::Z80::PartialMachineCycle &cycle) {
using PartialMachineCycle = CPU::Z80::PartialMachineCycle;
const uint16_t address = cycle.address ? *cycle.address : 0x0000;
if(
is_contended_[address >> 14] &&
cycle.operation >= PartialMachineCycle::ReadOpcodeStart &&
cycle.operation <= PartialMachineCycle::WriteStart) {
// Apply contention if necessary.
//
// Assumption here: the trigger for the ULA inserting a delay is the falling edge
// of MREQ, which is always half a cycle into a read or write.
//
// TODO: somehow provide that information in the PartialMachineCycle?
const HalfCycles delay = video_.last_valid()->access_delay(video_.time_since_flush() + HalfCycles(1));
advance(cycle.length + delay);
return delay;
}
// TODO: for read/write this should advance only until the rising edge of MREQ, then do
// the read/write, then complete the bus cycle. Only via the 48/128k Spectrum contended
// timings am I now learning what happens with MREQ during extended read/write bus cycles
// (i.e. those longer than 3 cycles)
if(cycle.length > HalfCycles(3)) {
advance(HalfCycles(3));
} else {
advance(cycle.length);
}
switch(cycle.operation) {
default: break;
case PartialMachineCycle::ReadOpcode:
// Fast loading: ROM version.
//
// The below patches over the 'LD-BYTES' routine from the 48kb ROM.
if(use_fast_tape_hack_ && address == 0x0556 && read_pointers_[0] == &rom_[0xc000]) {
if(perform_rom_ld_bytes()) {
// Stop pressing enter, if neccessry.
if(duration_to_press_enter_ > Cycles(0)) {
duration_to_press_enter_ = Cycles(0);
keyboard_.set_key_state(ZX::Keyboard::KeyEnter, false);
}
*cycle.value = 0xc9; // i.e. RET.
break;
}
}
case PartialMachineCycle::Read:
*cycle.value = read_pointers_[address >> 14][address];
if(is_contended_[address >> 14]) {
video_->set_last_contended_area_access(*cycle.value);
}
break;
case PartialMachineCycle::Write:
// Flush video if this access modifies screen contents.
if(is_video_[address >> 14] && (address & 0x3fff) < 6912) {
video_.flush();
}
write_pointers_[address >> 14][address] = *cycle.value;
// Fill the floating bus buffer if this write is within the contended area.
if(is_contended_[address >> 14]) {
video_->set_last_contended_area_access(*cycle.value);
}
break;
case PartialMachineCycle::Output:
// Test for port FE.
if(!(address&1)) {
update_audio();
audio_toggle_.set_output(*cycle.value & 0x10);
video_->set_border_colour(*cycle.value & 7);
// b0b2: border colour
// b3: enable tape input (?)
// b4: tape and speaker output
}
// Test for classic 128kb paging register (i.e. port 7ffd).
if((address & 0xc002) == 0x4000) {
port7ffd_ = *cycle.value;
update_memory_map();
// Set the proper video base pointer.
set_video_address();
// Potentially lock paging, _after_ the current
// port values have taken effect.
disable_paging_ |= *cycle.value & 0x20;
}
// Test for +2a/+3 paging (i.e. port 1ffd).
if((address & 0xf002) == 0x1000) {
port1ffd_ = *cycle.value;
update_memory_map();
update_video_base();
if constexpr (model == Model::Plus3) {
fdc_->set_motor_on(*cycle.value & 0x08);
}
}
if((address & 0xc002) == 0xc000) {
// Select AY register.
update_audio();
GI::AY38910::Utility::select_register(ay_, *cycle.value);
}
if((address & 0xc002) == 0x8000) {
// Write to AY register.
update_audio();
GI::AY38910::Utility::write_data(ay_, *cycle.value);
}
if constexpr (model == Model::Plus3) {
switch(address) {
default: break;
case 0x3ffd: case 0x2ffd:
fdc_->write((address >> 12) & 1, *cycle.value);
break;
}
}
break;
case PartialMachineCycle::Input:
*cycle.value = 0xff;
if(!(address&1)) {
// Port FE:
//
// address b8+: mask of keyboard lines to select
// result: b0b4: mask of keys pressed
// b6: tape input
*cycle.value &= keyboard_.read(address);
*cycle.value &= tape_player_.get_input() ? 0xbf : 0xff;
// If this read is within 200 cycles of the previous,
// count it as an adjacent hit; if 20 of those have
// occurred then start the tape motor.
if(use_automatic_tape_motor_control_) {
if(cycles_since_tape_input_read_ < HalfCycles(400)) {
++recent_tape_hits_;
if(recent_tape_hits_ == 20) {
tape_player_.set_motor_control(true);
}
} else {
recent_tape_hits_ = 0;
}
cycles_since_tape_input_read_ = HalfCycles(0);
}
}
if((address & 0xc002) == 0xc000) {
// Read from AY register.
update_audio();
*cycle.value &= GI::AY38910::Utility::read(ay_);
}
// Check for a floating bus read; these are particularly arcane
// on the +2a/+3. See footnote to https://spectrumforeveryone.com/technical/memory-contention-floating-bus/
// and, much more rigorously, http://sky.relative-path.com/zx/floating_bus.html
if(!disable_paging_ && (address & 0xf003) == 0x0001) {
*cycle.value &= video_->get_floating_value();
}
if constexpr (model == Model::Plus3) {
switch(address) {
default: break;
case 0x3ffd: case 0x2ffd:
*cycle.value &= fdc_->read((address >> 12) & 1);
break;
}
}
break;
}
if(cycle.length > HalfCycles(3)) {
advance(cycle.length - HalfCycles(3));
}
return HalfCycles(0);
}
private:
void advance(HalfCycles duration) {
time_since_audio_update_ += duration;
video_ += duration;
if(video_.did_flush()) {
z80_.set_interrupt_line(video_.last_valid()->get_interrupt_line());
}
if(!tape_player_is_sleeping_) tape_player_.run_for(duration.as_integral());
// Update automatic tape motor control, if enabled; if it's been
// 3 seconds since software last possibly polled the tape, stop it.
if(use_automatic_tape_motor_control_ && cycles_since_tape_input_read_ < HalfCycles(clock_rate() * 6)) {
cycles_since_tape_input_read_ += duration;
if(cycles_since_tape_input_read_ >= HalfCycles(clock_rate() * 6)) {
tape_player_.set_motor_control(false);
recent_tape_hits_ = 0;
}
}
if constexpr (model == Model::Plus3) {
fdc_ += Cycles(duration.as_integral());
}
if(typer_) typer_->run_for(duration);
}
void type_string(const std::string &string) override {
Utility::TypeRecipient<CharacterMapper>::add_typer(string);
}
bool can_type(char c) const override {
return Utility::TypeRecipient<CharacterMapper>::can_type(c);
}
public:
// MARK: - Typer.
HalfCycles get_typer_delay(const std::string &) const override {
return z80_.get_is_resetting() ? Cycles(7'000'000) : Cycles(0);
}
HalfCycles get_typer_frequency() const override{
return Cycles(70'908);
}
KeyboardMapper *get_keyboard_mapper() override {
return &keyboard_mapper_;
}
// MARK: - Keyboard.
void set_key_state(uint16_t key, bool is_pressed) override {
keyboard_.set_key_state(key, is_pressed);
}
void clear_all_keys() override {
keyboard_.clear_all_keys();
// Caveat: if holding enter synthetically, continue to do so.
if(duration_to_press_enter_ > Cycles(0)) {
keyboard_.set_key_state(ZX::Keyboard::KeyEnter, true);
}
}
// MARK: - MediaTarget.
bool insert_media(const Analyser::Static::Media &media) override {
// If there are any tapes supplied, use the first of them.
if(!media.tapes.empty()) {
tape_player_.set_tape(media.tapes.front());
set_use_fast_tape();
}
// Insert up to four disks.
int c = 0;
for(auto &disk : media.disks) {
fdc_->set_disk(disk, c);
c++;
if(c == 4) break;
}
return !media.tapes.empty() || (!media.disks.empty() && model == Model::Plus3);
}
// MARK: - ClockingHint::Observer.
void set_component_prefers_clocking(ClockingHint::Source *, ClockingHint::Preference) override {
tape_player_is_sleeping_ = tape_player_.preferred_clocking() == ClockingHint::Preference::None;
}
// MARK: - Tape control.
void set_use_automatic_tape_motor_control(bool enabled) {
use_automatic_tape_motor_control_ = enabled;
if(!enabled) {
tape_player_.set_motor_control(false);
}
}
void set_tape_is_playing(bool is_playing) final {
tape_player_.set_motor_control(is_playing);
}
bool get_tape_is_playing() final {
return tape_player_.get_motor_control();
}
// MARK: - Configuration options.
std::unique_ptr<Reflection::Struct> get_options() override {
auto options = std::make_unique<Options>(Configurable::OptionsType::UserFriendly); // OptionsType is arbitrary, but not optional.
options->automatic_tape_motor_control = use_automatic_tape_motor_control_;
options->quickload = allow_fast_tape_hack_;
return options;
}
void set_options(const std::unique_ptr<Reflection::Struct> &str) override {
const auto options = dynamic_cast<Options *>(str.get());
set_video_signal_configurable(options->output);
set_use_automatic_tape_motor_control(options->automatic_tape_motor_control);
allow_fast_tape_hack_ = options->quickload;
set_use_fast_tape();
}
// MARK: - AudioProducer.
Outputs::Speaker::Speaker *get_speaker() override {
return &speaker_;
}
// MARK: - Activity Source.
void set_activity_observer(Activity::Observer *observer) override {
if constexpr (model == Model::Plus3) fdc_->set_activity_observer(observer);
tape_player_.set_activity_observer(observer);
}
private:
CPU::Z80::Processor<ConcreteMachine, false, false> z80_;
// MARK: - Memory.
std::array<uint8_t, 64*1024> rom_;
std::array<uint8_t, 128*1024> ram_;
std::array<uint8_t, 16*1024> scratch_;
const uint8_t *read_pointers_[4];
uint8_t *write_pointers_[4];
uint8_t pages_[4];
bool is_contended_[4];
bool is_video_[4];
uint8_t port1ffd_ = 0;
uint8_t port7ffd_ = 0;
bool disable_paging_ = false;
void update_memory_map() {
// If paging is permanently disabled, don't react.
if(disable_paging_) {
return;
}
if(port1ffd_ & 0x01) {
// "Special paging mode", i.e. one of four fixed
// RAM configurations, port 7ffd doesn't matter.
switch(port1ffd_ & 0x06) {
default:
case 0x00:
set_memory(0, 0);
set_memory(1, 1);
set_memory(2, 2);
set_memory(3, 3);
break;
case 0x02:
set_memory(0, 4);
set_memory(1, 5);
set_memory(2, 6);
set_memory(3, 7);
break;
case 0x04:
set_memory(0, 4);
set_memory(1, 5);
set_memory(2, 6);
set_memory(3, 3);
break;
case 0x06:
set_memory(0, 4);
set_memory(1, 7);
set_memory(2, 6);
set_memory(3, 3);
break;
}
} else {
// Apply standard 128kb-esque mapping (albeit with extra ROM to pick from).
set_memory(0, 0x80 | ((port1ffd_ >> 1) & 2) | ((port7ffd_ >> 4) & 1));
set_memory(1, 5);
set_memory(2, 2);
set_memory(3, port7ffd_ & 7);
}
}
void set_memory(int bank, uint8_t source) {
is_contended_[bank] = (source >= 4 && source < 8);
pages_[bank] = source;
uint8_t *read = (source < 0x80) ? &ram_[source * 16384] : &rom_[(source & 0x7f) * 16384];
const auto offset = bank*16384;
read_pointers_[bank] = read - offset;
write_pointers_[bank] = ((source < 0x80) ? read : scratch_.data()) - offset;
}
void set_video_address() {
video_->set_video_source(&ram_[((port7ffd_ & 0x08) ? 7 : 5) * 16384]);
update_video_base();
}
void update_video_base() {
const uint8_t video_page = (port7ffd_ & 0x08) ? 7 : 5;
is_video_[0] = pages_[0] == video_page;
is_video_[1] = pages_[1] == video_page;
is_video_[2] = pages_[2] == video_page;
is_video_[3] = pages_[3] == video_page;
}
// MARK: - Audio.
Concurrency::DeferringAsyncTaskQueue audio_queue_;
GI::AY38910::AY38910<false> ay_;
Audio::Toggle audio_toggle_;
Outputs::Speaker::CompoundSource<GI::AY38910::AY38910<false>, Audio::Toggle> mixer_;
Outputs::Speaker::LowpassSpeaker<Outputs::Speaker::CompoundSource<GI::AY38910::AY38910<false>, Audio::Toggle>> speaker_;
HalfCycles time_since_audio_update_;
void update_audio() {
speaker_.run_for(audio_queue_, time_since_audio_update_.divide_cycles(Cycles(2)));
}
// MARK: - Video.
static constexpr VideoTiming video_timing = VideoTiming::Plus3;
JustInTimeActor<Video<video_timing>> video_;
// MARK: - Keyboard.
Sinclair::ZX::Keyboard::Keyboard keyboard_;
Sinclair::ZX::Keyboard::KeyboardMapper keyboard_mapper_;
// MARK: - Tape.
Storage::Tape::BinaryTapePlayer tape_player_;
bool tape_player_is_sleeping_ = false;
bool use_automatic_tape_motor_control_ = true;
HalfCycles cycles_since_tape_input_read_;
int recent_tape_hits_ = 0;
bool allow_fast_tape_hack_ = false;
bool use_fast_tape_hack_ = false;
void set_use_fast_tape() {
use_fast_tape_hack_ = allow_fast_tape_hack_ && tape_player_.has_tape();
}
// Reimplements the 'LD-BYTES' routine, as documented at
// https://skoolkid.github.io/rom/asm/0556.html i.e.
//
// In:
// A: 0x00 or 0xff for block type;
// F: carry set if loading, clear if verifying;
// DE: block length;
// IX: start address.
//
// Out:
// F: carry set for success, clear for error.
bool perform_rom_ld_bytes() {
using Parser = Storage::Tape::ZXSpectrum::Parser;
Parser parser(Parser::MachineType::ZXSpectrum);
using Register = CPU::Z80::Register;
uint8_t flags = uint8_t(z80_.get_value_of_register(Register::Flags));
if(!(flags & 1)) return false;
const uint8_t block_type = uint8_t(z80_.get_value_of_register(Register::A));
const auto block = parser.find_block(tape_player_.get_tape());
if(!block || block_type != (*block).type) return false;
uint16_t length = z80_.get_value_of_register(Register::DE);
uint16_t target = z80_.get_value_of_register(Register::IX);
while(length--) {
auto next = parser.get_byte(tape_player_.get_tape());
if(!next) {
flags &= ~1;
break;
}
write_pointers_[target >> 14][target] = *next;
++target;
}
z80_.set_value_of_register(Register::Flags, flags);
return true;
}
// MARK: - Disc.
JustInTimeActor<Amstrad::FDC, Cycles> fdc_;
// MARK: - Automatic startup.
Cycles duration_to_press_enter_;
};
}
}
using namespace Sinclair::ZXSpectrum;
Machine *Machine::ZXSpectrum(const Analyser::Static::Target *target, const ROMMachine::ROMFetcher &rom_fetcher) {
const auto zx_target = dynamic_cast<const Analyser::Static::ZXSpectrum::Target *>(target);
switch(zx_target->model) {
case Model::Plus2a: return new ConcreteMachine<Model::Plus2a>(*zx_target, rom_fetcher);
case Model::Plus3: return new ConcreteMachine<Model::Plus3>(*zx_target, rom_fetcher);
}
return nullptr;
}
Machine::~Machine() {}