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136 lines
3.4 KiB
C++
136 lines
3.4 KiB
C++
//
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// Tape.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 03/12/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#include "Tape.hpp"
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using namespace Electron;
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Tape::Tape() :
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TapePlayer(2000000),
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is_running_(false),
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data_register_(0),
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delegate_(nullptr),
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output_({.bits_remaining_until_empty = 0, .cycles_into_pulse = 0}),
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last_posted_interrupt_status_(0),
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interrupt_status_(0)
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{}
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void Tape::push_tape_bit(uint16_t bit)
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{
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data_register_ = (uint16_t)((data_register_ >> 1) | (bit << 10));
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if(input_.minimum_bits_until_full) input_.minimum_bits_until_full--;
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if(input_.minimum_bits_until_full == 8) interrupt_status_ &= ~Interrupt::ReceiveDataFull;
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if(!input_.minimum_bits_until_full)
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{
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if((data_register_&0x3) == 0x1)
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{
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interrupt_status_ |= Interrupt::ReceiveDataFull;
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if(is_in_input_mode_) input_.minimum_bits_until_full = 9;
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}
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}
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if(output_.bits_remaining_until_empty) output_.bits_remaining_until_empty--;
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if(!output_.bits_remaining_until_empty) interrupt_status_ |= Interrupt::TransmitDataEmpty;
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if(data_register_ == 0x3ff) interrupt_status_ |= Interrupt::HighToneDetect;
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else interrupt_status_ &= ~Interrupt::HighToneDetect;
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evaluate_interrupts();
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}
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void Tape::evaluate_interrupts()
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{
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if(last_posted_interrupt_status_ != interrupt_status_)
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{
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last_posted_interrupt_status_ = interrupt_status_;
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if(delegate_) delegate_->tape_did_change_interrupt_status(this);
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}
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}
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void Tape::clear_interrupts(uint8_t interrupts)
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{
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interrupt_status_ &= ~interrupts;
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evaluate_interrupts();
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}
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void Tape::set_is_in_input_mode(bool is_in_input_mode)
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{
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is_in_input_mode_ = is_in_input_mode;
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}
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void Tape::set_counter(uint8_t value)
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{
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output_.cycles_into_pulse = 0;
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output_.bits_remaining_until_empty = 0;
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}
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void Tape::set_data_register(uint8_t value)
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{
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data_register_ = (uint16_t)((value << 2) | 1);
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output_.bits_remaining_until_empty = 9;
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}
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uint8_t Tape::get_data_register()
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{
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return (uint8_t)(data_register_ >> 2);
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}
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void Tape::process_input_pulse(Storage::Tape::Tape::Pulse pulse)
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{
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crossings_[0] = crossings_[1];
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crossings_[1] = crossings_[2];
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crossings_[2] = crossings_[3];
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crossings_[3] = Tape::Unrecognised;
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if(pulse.type != Storage::Tape::Tape::Pulse::Zero)
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{
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float pulse_length = (float)pulse.length.length / (float)pulse.length.clock_rate;
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if(pulse_length >= 0.35 / 2400.0 && pulse_length < 0.7 / 2400.0) crossings_[3] = Tape::Short;
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if(pulse_length >= 0.35 / 1200.0 && pulse_length < 0.7 / 1200.0) crossings_[3] = Tape::Long;
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}
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if(crossings_[0] == Tape::Long && crossings_[1] == Tape::Long)
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{
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push_tape_bit(0);
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crossings_[0] = crossings_[1] = Tape::Recognised;
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}
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else
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{
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if(crossings_[0] == Tape::Short && crossings_[1] == Tape::Short && crossings_[2] == Tape::Short && crossings_[3] == Tape::Short)
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{
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push_tape_bit(1);
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crossings_[0] = crossings_[1] =
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crossings_[2] = crossings_[3] = Tape::Recognised;
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}
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}
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}
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void Tape::run_for_cycles(unsigned int number_of_cycles)
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{
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if(is_enabled_)
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{
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if(is_in_input_mode_)
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{
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if(is_running_)
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{
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TapePlayer::run_for_cycles((int)number_of_cycles);
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}
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}
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else
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{
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output_.cycles_into_pulse += number_of_cycles;
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while(output_.cycles_into_pulse > 1664) // 1664 = the closest you can get to 1200 baud if you're looking for something
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{ // that divides the 125,000Hz clock that the sound divider runs off.
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output_.cycles_into_pulse -= 1664;
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push_tape_bit(1);
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}
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}
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}
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}
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