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354 lines
11 KiB
C++
354 lines
11 KiB
C++
//
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// Archimedes.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 04/03/2024.
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// Copyright © 2024 Thomas Harte. All rights reserved.
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//
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#include "Archimedes.hpp"
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#include "HalfDuplexSerial.hpp"
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#include "InputOutputController.hpp"
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#include "Keyboard.hpp"
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#include "KeyboardMapper.hpp"
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#include "MemoryController.hpp"
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#include "Sound.hpp"
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#include "../../AudioProducer.hpp"
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#include "../../KeyboardMachine.hpp"
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#include "../../MediaTarget.hpp"
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#include "../../MouseMachine.hpp"
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#include "../../ScanProducer.hpp"
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#include "../../TimedMachine.hpp"
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#include "../../../Activity/Source.hpp"
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#include "../../../InstructionSets/ARM/Disassembler.hpp"
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#include "../../../InstructionSets/ARM/Executor.hpp"
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#include "../../../Outputs/Log.hpp"
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#include "../../../Components/I2C/I2C.hpp"
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#include <algorithm>
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#include <array>
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#include <set>
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#include <vector>
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namespace Archimedes {
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class ConcreteMachine:
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public Machine,
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public MachineTypes::AudioProducer,
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public MachineTypes::MappedKeyboardMachine,
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public MachineTypes::MediaTarget,
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public MachineTypes::MouseMachine,
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public MachineTypes::TimedMachine,
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public MachineTypes::ScanProducer,
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public Activity::Source
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{
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private:
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Log::Logger<Log::Source::Archimedes> logger;
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// This fictitious clock rate just means '24 MIPS, please'; it's divided elsewhere.
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static constexpr int ClockRate = 24'000'000;
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// Runs for 24 cycles, distributing calls to the various ticking subsystems
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// 'correctly' (i.e. correctly for the approximation in use).
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//
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// The implementation of this is coupled to the ClockRate above, hence its
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// appearance here.
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template <int video_divider, bool original_speed>
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void macro_tick() {
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macro_counter_ -= 24;
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// This is a 24-cycle window, so at 24Mhz macro_tick() is called at 1Mhz.
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// Hence, required ticks are:
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//
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// * CPU: 24;
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// * video: 24 / video_divider;
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// * floppy: 8;
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// * timers: 2;
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// * sound: 1.
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tick_cpu_video<0, video_divider, original_speed>(); tick_cpu_video<1, video_divider, original_speed>();
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tick_cpu_video<2, video_divider, original_speed>(); tick_floppy();
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tick_cpu_video<3, video_divider, original_speed>(); tick_cpu_video<4, video_divider, original_speed>();
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tick_cpu_video<5, video_divider, original_speed>(); tick_floppy();
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tick_cpu_video<6, video_divider, original_speed>(); tick_cpu_video<7, video_divider, original_speed>();
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tick_cpu_video<8, video_divider, original_speed>(); tick_floppy();
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tick_cpu_video<9, video_divider, original_speed>(); tick_cpu_video<10, video_divider, original_speed>();
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tick_cpu_video<11, video_divider, original_speed>(); tick_floppy();
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tick_timers();
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tick_cpu_video<12, video_divider, original_speed>(); tick_cpu_video<13, video_divider, original_speed>();
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tick_cpu_video<14, video_divider, original_speed>(); tick_floppy();
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tick_cpu_video<15, video_divider, original_speed>(); tick_cpu_video<16, video_divider, original_speed>();
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tick_cpu_video<17, video_divider, original_speed>(); tick_floppy();
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tick_cpu_video<18, video_divider, original_speed>(); tick_cpu_video<19, video_divider, original_speed>();
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tick_cpu_video<20, video_divider, original_speed>(); tick_floppy();
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tick_cpu_video<21, video_divider, original_speed>(); tick_cpu_video<22, video_divider, original_speed>();
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tick_cpu_video<23, video_divider, original_speed>(); tick_floppy();
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tick_timers();
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tick_sound();
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}
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int macro_counter_ = 0;
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template <int offset, int video_divider, bool original_speed>
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void tick_cpu_video() {
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if constexpr (!(offset % video_divider)) {
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tick_video();
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}
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// Debug mode: run CPU a lot slower. Actually at close to original advertised MIPS speed.
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if constexpr (original_speed && (offset & 7)) return;
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if constexpr (offset & 1) return;
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tick_cpu();
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}
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public:
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ConcreteMachine(
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const Analyser::Static::Target &target,
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const ROMMachine::ROMFetcher &rom_fetcher
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) : executor_(*this, *this, *this) {
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set_clock_rate(ClockRate);
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constexpr ROM::Name risc_os = ROM::Name::AcornRISCOS311;
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ROM::Request request(risc_os);
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auto roms = rom_fetcher(request);
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if(!request.validate(roms)) {
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throw ROMMachine::Error::MissingROMs;
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}
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executor_.bus.set_rom(roms.find(risc_os)->second);
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insert_media(target.media);
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fill_pipeline(0);
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}
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void update_interrupts() {
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using Exception = InstructionSet::ARM::Registers::Exception;
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const int requests = executor_.bus.interrupt_mask();
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if((requests & InterruptRequests::FIQ) && executor_.registers().would_interrupt<Exception::FIQ>()) {
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pipeline_.reschedule(Pipeline::SWISubversion::FIQ);
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return;
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}
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if((requests & InterruptRequests::IRQ) && executor_.registers().would_interrupt<Exception::IRQ>()) {
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pipeline_.reschedule(Pipeline::SWISubversion::IRQ);
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}
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}
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void did_set_status() {
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// This might have been a change of mode, so...
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trans_ = executor_.registers().mode() == InstructionSet::ARM::Mode::User;
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fill_pipeline(executor_.pc());
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update_interrupts();
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}
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void did_set_pc() {
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fill_pipeline(executor_.pc());
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}
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bool should_swi(uint32_t) {
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using Exception = InstructionSet::ARM::Registers::Exception;
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using SWISubversion = Pipeline::SWISubversion;
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switch(pipeline_.swi_subversion()) {
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case Pipeline::SWISubversion::None:
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return true;
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case SWISubversion::DataAbort:
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// executor_.set_pc(executor_.pc() - 4);
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executor_.registers().exception<Exception::DataAbort>();
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break;
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// FIQ and IRQ decrement the PC because their apperance in the pipeline causes
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// it to look as though they were fetched, but they weren't.
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case SWISubversion::FIQ:
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executor_.set_pc(executor_.pc() - 4);
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executor_.registers().exception<Exception::FIQ>();
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break;
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case SWISubversion::IRQ:
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executor_.set_pc(executor_.pc() - 4);
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executor_.registers().exception<Exception::IRQ>();
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break;
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}
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did_set_pc();
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return false;
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}
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void update_clock_rates() {
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video_divider_ = executor_.bus.video().clock_divider();
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}
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private:
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// MARK: - ScanProducer.
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void set_scan_target(Outputs::Display::ScanTarget *scan_target) override {
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executor_.bus.video().crt().set_scan_target(scan_target);
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}
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Outputs::Display::ScanStatus get_scaled_scan_status() const override {
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return executor_.bus.video().crt().get_scaled_scan_status() * video_divider_;
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}
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// MARK: - TimedMachine.
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int video_divider_ = 1;
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void run_for(Cycles cycles) override {
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#ifndef NDEBUG
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// Debug mode: always run 'slowly' because that's less of a burden, and
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// because it allows me to peer at problems with greater leisure.
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const bool use_original_speed = true;
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#else
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// As a first, blunt implementation: try to model something close
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// to original speed if there have been 10 frame rate overages in total.
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const bool use_original_speed = executor_.bus.video().frame_rate_overages() > 10;
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#endif
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if(use_original_speed) run_for<true>(cycles);
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else run_for<false>(cycles);
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}
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template <bool original_speed>
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void run_for(Cycles cycles) {
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macro_counter_ += cycles.as<int>();
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while(macro_counter_ > 0) {
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switch(video_divider_) {
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default: macro_tick<2, original_speed>(); break;
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case 3: macro_tick<3, original_speed>(); break;
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case 4: macro_tick<4, original_speed>(); break;
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case 6: macro_tick<6, original_speed>(); break;
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}
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}
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}
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void tick_cpu() {
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const uint32_t instruction = advance_pipeline(executor_.pc() + 8);
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InstructionSet::ARM::execute(instruction, executor_);
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}
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void tick_timers() { executor_.bus.tick_timers(); }
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void tick_sound() { executor_.bus.sound().tick(); }
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void tick_video() { executor_.bus.video().tick(); }
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void tick_floppy() { executor_.bus.tick_floppy(); }
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// MARK: - MediaTarget
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bool insert_media(const Analyser::Static::Media &media) override {
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size_t c = 0;
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for(auto &disk : media.disks) {
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executor_.bus.set_disk(disk, c);
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c++;
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if(c == 4) break;
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}
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return true;
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}
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// MARK: - AudioProducer
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Outputs::Speaker::Speaker *get_speaker() override {
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return executor_.bus.speaker();
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}
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// MARK: - Activity::Source.
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void set_activity_observer(Activity::Observer *observer) final {
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executor_.bus.set_activity_observer(observer);
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}
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// MARK: - MappedKeyboardMachine.
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MappedKeyboardMachine::KeyboardMapper *get_keyboard_mapper() override {
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return &keyboard_mapper_;
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}
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Archimedes::KeyboardMapper keyboard_mapper_;
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void set_key_state(uint16_t key, bool is_pressed) override {
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const int row = Archimedes::KeyboardMapper::row(key);
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const int column = Archimedes::KeyboardMapper::column(key);
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executor_.bus.keyboard().set_key_state(row, column, is_pressed);
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}
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// MARK: - MouseMachine.
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Inputs::Mouse &get_mouse() override {
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return executor_.bus.keyboard().mouse();
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}
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// MARK: - ARM execution.
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static constexpr auto arm_model = InstructionSet::ARM::Model::ARMv2;
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using Executor = InstructionSet::ARM::Executor<arm_model, MemoryController<ConcreteMachine, ConcreteMachine>, ConcreteMachine>;
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Executor executor_;
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bool trans_ = false;
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void fill_pipeline(uint32_t pc) {
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if(pipeline_.interrupt_next()) return;
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advance_pipeline(pc);
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advance_pipeline(pc + 4);
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}
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uint32_t advance_pipeline(uint32_t pc) {
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uint32_t instruction = 0; // Value should never be used; this avoids a spurious GCC warning.
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const bool did_read = executor_.bus.read(pc, instruction, trans_);
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return pipeline_.exchange(
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did_read ? instruction : Pipeline::SWI,
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did_read ? Pipeline::SWISubversion::None : Pipeline::SWISubversion::DataAbort);
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}
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struct Pipeline {
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enum SWISubversion: uint8_t {
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None,
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DataAbort,
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IRQ,
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FIQ,
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};
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static constexpr uint32_t SWI = 0xef'000000;
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uint32_t exchange(uint32_t next, SWISubversion subversion) {
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const uint32_t result = upcoming_[active_].opcode;
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latched_subversion_ = upcoming_[active_].subversion;
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upcoming_[active_].opcode = next;
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upcoming_[active_].subversion = subversion;
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active_ ^= 1;
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return result;
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}
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SWISubversion swi_subversion() const {
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return latched_subversion_;
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}
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// TODO: one day, possibly: schedule the subversion one slot further into the future
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// (i.e. active_ ^ 1) to allow one further instruction to occur as usual before the
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// action paplies. That is, if interrupts take effect one instruction later after a flags
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// change, which I don't yet know.
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//
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// In practice I got into a bit of a race condition between interrupt scheduling and
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// flags changes, so have backed off for now.
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void reschedule(SWISubversion subversion) {
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upcoming_[active_].opcode = SWI;
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upcoming_[active_].subversion = subversion;
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}
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bool interrupt_next() const {
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return upcoming_[active_].subversion == SWISubversion::IRQ || upcoming_[active_].subversion == SWISubversion::FIQ;
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}
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private:
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struct Stage {
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uint32_t opcode;
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SWISubversion subversion = SWISubversion::None;
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};
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Stage upcoming_[2];
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int active_ = 0;
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SWISubversion latched_subversion_;
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} pipeline_;
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};
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}
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using namespace Archimedes;
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std::unique_ptr<Machine> Machine::Archimedes(const Analyser::Static::Target *target, const ROMMachine::ROMFetcher &rom_fetcher) {
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return std::make_unique<ConcreteMachine>(*target, rom_fetcher);
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}
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