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485 lines
12 KiB
C++
485 lines
12 KiB
C++
//
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// Electron.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 03/01/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#include "Electron.hpp"
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using namespace Electron;
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#pragma mark - Lifecycle
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Machine::Machine() :
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interrupt_control_(0),
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interrupt_status_(Interrupt::PowerOnReset | Interrupt::TransmitDataEmpty | 0x80),
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cycles_since_display_update_(0),
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cycles_since_audio_update_(0),
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use_fast_tape_hack_(false),
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cycles_until_display_interrupt_(0)
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{
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memset(key_states_, 0, sizeof(key_states_));
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for(int c = 0; c < 16; c++)
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memset(roms_[c], 0xff, 16384);
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tape_.set_delegate(this);
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set_clock_rate(2000000);
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}
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#pragma mark - Output
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void Machine::setup_output(float aspect_ratio)
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{
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video_output_.reset(new VideoOutput(ram_));
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// The maximum output frequency is 62500Hz and all other permitted output frequencies are integral divisions of that;
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// however setting the speaker on or off can happen on any 2Mhz cycle, and probably (?) takes effect immediately. So
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// run the speaker at a 2000000Hz input rate, at least for the time being.
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speaker_.reset(new Speaker);
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speaker_->set_input_rate(2000000 / Speaker::clock_rate_divider);
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}
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void Machine::close_output()
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{
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video_output_.reset();
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}
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std::shared_ptr<Outputs::CRT::CRT> Machine::get_crt()
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{
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return video_output_->get_crt();
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}
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std::shared_ptr<Outputs::Speaker> Machine::get_speaker()
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{
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return speaker_;
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}
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#pragma mark - The keyboard
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void Machine::clear_all_keys()
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{
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memset(key_states_, 0, sizeof(key_states_));
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if(is_holding_shift_) set_key_state(KeyShift, true);
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}
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void Machine::set_key_state(uint16_t key, bool isPressed)
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{
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if(key == KeyBreak)
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{
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set_reset_line(isPressed);
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}
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else
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{
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if(isPressed)
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key_states_[key >> 4] |= key&0xf;
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else
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key_states_[key >> 4] &= ~(key&0xf);
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}
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}
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#pragma mark - Machine configuration
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void Machine::configure_as_target(const StaticAnalyser::Target &target)
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{
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if(target.tapes.size())
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{
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tape_.set_tape(target.tapes.front());
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}
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if(target.disks.size())
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{
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plus3_.reset(new Plus3);
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if(target.acorn.has_dfs)
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{
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set_rom(ROMSlot0, dfs_, true);
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}
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if(target.acorn.has_adfs)
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{
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set_rom(ROMSlot4, adfs_, true);
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set_rom(ROMSlot5, std::vector<uint8_t>(adfs_.begin() + 16384, adfs_.end()), true);
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}
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plus3_->set_disk(target.disks.front(), 0);
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}
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ROMSlot slot = ROMSlot12;
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for(std::shared_ptr<Storage::Cartridge::Cartridge> cartridge : target.cartridges)
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{
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set_rom(slot, cartridge->get_segments().front().data, false);
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slot = (ROMSlot)(((int)slot + 1)&15);
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}
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if(target.loadingCommand.length()) // TODO: and automatic loading option enabled
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{
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set_typer_for_string(target.loadingCommand.c_str());
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}
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if(target.acorn.should_shift_restart)
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{
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shift_restart_counter_ = 1000000;
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}
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}
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void Machine::set_rom(ROMSlot slot, std::vector<uint8_t> data, bool is_writeable)
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{
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uint8_t *target = nullptr;
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switch(slot)
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{
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case ROMSlotDFS: dfs_ = data; return;
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case ROMSlotADFS: adfs_ = data; return;
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case ROMSlotOS: target = os_; break;
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default:
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target = roms_[slot];
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rom_write_masks_[slot] = is_writeable;
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break;
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}
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memcpy(target, &data[0], std::min((size_t)16384, data.size()));
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}
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#pragma mark - The bus
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unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value)
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{
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unsigned int cycles = 1;
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if(address < 0x8000)
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{
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if(isReadOperation(operation))
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{
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*value = ram_[address];
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}
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else
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{
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if(address >= video_access_range_.low_address && address <= video_access_range_.high_address) update_display();
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ram_[address] = *value;
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}
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// for the entire frame, RAM is accessible only on odd cycles; in modes below 4
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// it's also accessible only outside of the pixel regions
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cycles += video_output_->get_cycles_until_next_ram_availability((int)(cycles_since_display_update_ + 1));
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}
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else
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{
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switch(address & 0xff0f)
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{
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case 0xfe00:
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if(isReadOperation(operation))
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{
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*value = interrupt_status_;
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interrupt_status_ &= ~PowerOnReset;
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}
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else
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{
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interrupt_control_ = (*value) & ~1;
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evaluate_interrupts();
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}
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break;
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case 0xfe07:
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if(!isReadOperation(operation))
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{
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// update speaker mode
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bool new_speaker_is_enabled = (*value & 6) == 2;
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if(new_speaker_is_enabled != speaker_is_enabled_)
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{
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update_audio();
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speaker_->set_is_enabled(new_speaker_is_enabled);
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speaker_is_enabled_ = new_speaker_is_enabled;
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}
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tape_.set_is_enabled((*value & 6) != 6);
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tape_.set_is_in_input_mode((*value & 6) == 0);
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tape_.set_is_running(((*value)&0x40) ? true : false);
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// TODO: caps lock LED
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}
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// deliberate fallthrough
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case 0xfe02: case 0xfe03:
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case 0xfe08: case 0xfe09: case 0xfe0a: case 0xfe0b:
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case 0xfe0c: case 0xfe0d: case 0xfe0e: case 0xfe0f:
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if(!isReadOperation(operation))
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{
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update_display();
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video_output_->set_register(address, *value);
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video_access_range_ = video_output_->get_memory_access_range();
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queue_next_display_interrupt();
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}
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break;
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case 0xfe04:
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if(isReadOperation(operation))
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{
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*value = tape_.get_data_register();
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tape_.clear_interrupts(Interrupt::ReceiveDataFull);
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}
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else
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{
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tape_.set_data_register(*value);
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tape_.clear_interrupts(Interrupt::TransmitDataEmpty);
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}
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break;
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case 0xfe05:
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if(!isReadOperation(operation))
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{
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const uint8_t interruptDisable = (*value)&0xf0;
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if( interruptDisable )
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{
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if( interruptDisable&0x10 ) interrupt_status_ &= ~Interrupt::DisplayEnd;
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if( interruptDisable&0x20 ) interrupt_status_ &= ~Interrupt::RealTimeClock;
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if( interruptDisable&0x40 ) interrupt_status_ &= ~Interrupt::HighToneDetect;
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evaluate_interrupts();
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// TODO: NMI
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}
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// latch the paged ROM in case external hardware is being emulated
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active_rom_ = (Electron::ROMSlot)(*value & 0xf);
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// apply the ULA's test
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if(*value & 0x08)
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{
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if(*value & 0x04)
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{
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keyboard_is_active_ = false;
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basic_is_active_ = false;
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}
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else
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{
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keyboard_is_active_ = !(*value & 0x02);
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basic_is_active_ = !keyboard_is_active_;
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}
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}
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}
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break;
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case 0xfe06:
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if(!isReadOperation(operation))
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{
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update_audio();
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speaker_->set_divider(*value);
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tape_.set_counter(*value);
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}
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break;
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case 0xfc04: case 0xfc05: case 0xfc06: case 0xfc07:
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if(plus3_ && (address&0x00f0) == 0x00c0)
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{
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if(is_holding_shift_ && address == 0xfcc4)
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{
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is_holding_shift_ = false;
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set_key_state(KeyShift, false);
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}
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if(isReadOperation(operation))
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*value = plus3_->get_register(address);
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else
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plus3_->set_register(address, *value);
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}
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break;
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case 0xfc00:
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if(plus3_ && (address&0x00f0) == 0x00c0)
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{
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if(!isReadOperation(operation))
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{
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plus3_->set_control_register(*value);
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}
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else
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*value = 1;
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}
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break;
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default:
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if(address >= 0xc000)
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{
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if(isReadOperation(operation))
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{
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if(
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use_fast_tape_hack_ &&
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tape_.has_tape() &&
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(operation == CPU6502::BusOperation::ReadOpcode) &&
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(
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(address == 0xf4e5) || (address == 0xf4e6) || // double NOPs at 0xf4e5, 0xf6de, 0xf6fa and 0xfa51
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(address == 0xf6de) || (address == 0xf6df) || // act to disable the normal branch into tape-handling
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(address == 0xf6fa) || (address == 0xf6fb) || // code, forcing the OS along the serially-accessed ROM
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(address == 0xfa51) || (address == 0xfa52) || // pathway.
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(address == 0xf0a8) // 0xf0a8 is from where a service call would normally be
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// dispatched; we can check whether it would be call 14
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// (i.e. read byte) and, if so, whether the OS was about to
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// issue a read byte call to a ROM despite being the tape
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// FS being selected. If so then this is a get byte that
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// we should service synthetically. Put the byte into Y
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// and set A to zero to report that action was taken, then
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// allow the PC read to return an RTS.
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)
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)
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{
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uint8_t service_call = (uint8_t)get_value_of_register(CPU6502::Register::X);
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if(address == 0xf0a8)
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{
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if(!ram_[0x247] && service_call == 14)
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{
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tape_.set_delegate(nullptr);
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// TODO: handle tape wrap around.
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int cycles_left_while_plausibly_in_data = 50;
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tape_.clear_interrupts(Interrupt::ReceiveDataFull);
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while(!tape_.get_tape()->is_at_end())
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{
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tape_.run_for_input_pulse();
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cycles_left_while_plausibly_in_data--;
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if(!cycles_left_while_plausibly_in_data) fast_load_is_in_data_ = false;
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if( (tape_.get_interrupt_status() & Interrupt::ReceiveDataFull) &&
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(fast_load_is_in_data_ || tape_.get_data_register() == 0x2a)
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) break;
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}
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tape_.set_delegate(this);
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tape_.clear_interrupts(Interrupt::ReceiveDataFull);
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interrupt_status_ |= tape_.get_interrupt_status();
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fast_load_is_in_data_ = true;
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set_value_of_register(CPU6502::Register::A, 0);
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set_value_of_register(CPU6502::Register::Y, tape_.get_data_register());
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*value = 0x60; // 0x60 is RTS
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}
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else
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*value = os_[address & 16383];
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}
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else
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*value = 0xea;
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}
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else
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{
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*value = os_[address & 16383];
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}
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}
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}
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else
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{
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if(isReadOperation(operation))
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{
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*value = roms_[active_rom_][address & 16383];
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if(keyboard_is_active_)
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{
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*value &= 0xf0;
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for(int address_line = 0; address_line < 14; address_line++)
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{
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if(!(address&(1 << address_line))) *value |= key_states_[address_line];
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}
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}
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if(basic_is_active_)
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{
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*value &= roms_[ROMSlotBASIC][address & 16383];
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}
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} else if(rom_write_masks_[active_rom_])
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{
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roms_[active_rom_][address & 16383] = *value;
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}
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}
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break;
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}
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}
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cycles_since_display_update_ += cycles;
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cycles_since_audio_update_ += cycles;
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if(cycles_since_audio_update_ > 16384) update_audio();
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tape_.run_for_cycles(cycles);
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cycles_until_display_interrupt_ -= cycles;
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if(cycles_until_display_interrupt_ < 0)
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{
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signal_interrupt(next_display_interrupt_);
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update_display();
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queue_next_display_interrupt();
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}
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if(typer_) typer_->update((int)cycles);
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if(plus3_) plus3_->run_for_cycles(4*cycles);
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if(shift_restart_counter_)
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{
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shift_restart_counter_ -= cycles;
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if(shift_restart_counter_ <= 0)
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{
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shift_restart_counter_ = 0;
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set_power_on(true);
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set_key_state(KeyShift, true);
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is_holding_shift_ = true;
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}
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}
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return cycles;
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}
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void Machine::synchronise()
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{
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update_display();
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update_audio();
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speaker_->flush();
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}
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#pragma mark - Deferred scheduling
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inline void Machine::update_display()
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{
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if(cycles_since_display_update_)
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{
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video_output_->run_for_cycles((int)cycles_since_display_update_);
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cycles_since_display_update_ = 0;
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}
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}
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inline void Machine::queue_next_display_interrupt()
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{
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VideoOutput::Interrupt next_interrupt = video_output_->get_next_interrupt();
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cycles_until_display_interrupt_ = next_interrupt.cycles;
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next_display_interrupt_ = next_interrupt.interrupt;
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}
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inline void Machine::update_audio()
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{
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if(cycles_since_audio_update_)
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{
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unsigned int difference = cycles_since_audio_update_ / Speaker::clock_rate_divider;
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cycles_since_audio_update_ %= Speaker::clock_rate_divider;
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speaker_->run_for_cycles(difference);
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}
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}
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#pragma mark - Interrupts
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inline void Machine::signal_interrupt(Electron::Interrupt interrupt)
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{
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interrupt_status_ |= interrupt;
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evaluate_interrupts();
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}
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inline void Machine::clear_interrupt(Electron::Interrupt interrupt)
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{
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interrupt_status_ &= ~interrupt;
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evaluate_interrupts();
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}
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inline void Machine::evaluate_interrupts()
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{
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if(interrupt_status_ & interrupt_control_)
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{
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interrupt_status_ |= 1;
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}
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else
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{
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interrupt_status_ &= ~1;
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}
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set_irq_line(interrupt_status_ & 1);
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}
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#pragma mark - Tape::Delegate
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void Machine::tape_did_change_interrupt_status(Tape *tape)
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{
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interrupt_status_ = (interrupt_status_ & ~(Interrupt::TransmitDataEmpty | Interrupt::ReceiveDataFull | Interrupt::HighToneDetect)) | tape_.get_interrupt_status();
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evaluate_interrupts();
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}
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