CLK/Machines/Electron/Tape.cpp

//
//  Tape.cpp
//  Clock Signal
//
//  Created by Thomas Harte on 03/12/2016.
//  Copyright © 2016 Thomas Harte. All rights reserved.
//

#include "Tape.hpp"

using namespace Electron;

Tape::Tape() :
	TapePlayer(2000000),
	is_running_(false),
	data_register_(0),
	delegate_(nullptr),
	output_({.bits_remaining_until_empty = 0, .cycles_into_pulse = 0}),
	last_posted_interrupt_status_(0),
	interrupt_status_(0)
{}

void Tape::push_tape_bit(uint16_t bit)
{
	data_register_ = (uint16_t)((data_register_ >> 1) | (bit << 10));

	if(input_.minimum_bits_until_full) input_.minimum_bits_until_full--;
	if(input_.minimum_bits_until_full == 8) interrupt_status_ &= ~Interrupt::ReceiveDataFull;
	if(!input_.minimum_bits_until_full)
	{
		if((data_register_&0x3) == 0x1)
		{
			interrupt_status_ |= Interrupt::ReceiveDataFull;
			if(is_in_input_mode_) input_.minimum_bits_until_full = 9;
		}
	}

	if(output_.bits_remaining_until_empty)	output_.bits_remaining_until_empty--;
	if(!output_.bits_remaining_until_empty)	interrupt_status_ |= Interrupt::TransmitDataEmpty;

	if(data_register_ == 0x3ff)	interrupt_status_ |= Interrupt::HighToneDetect;
	else						interrupt_status_ &= ~Interrupt::HighToneDetect;

	evaluate_interrupts();
}

void Tape::evaluate_interrupts()
{
	if(last_posted_interrupt_status_ != interrupt_status_)
	{
		last_posted_interrupt_status_ = interrupt_status_;
		if(delegate_) delegate_->tape_did_change_interrupt_status(this);
	}
}

void Tape::clear_interrupts(uint8_t interrupts)
{
	interrupt_status_ &= ~interrupts;
	evaluate_interrupts();
}

void Tape::set_is_in_input_mode(bool is_in_input_mode)
{
	is_in_input_mode_ = is_in_input_mode;
}

void Tape::set_counter(uint8_t value)
{
	output_.cycles_into_pulse = 0;
	output_.bits_remaining_until_empty = 0;
}

void Tape::set_data_register(uint8_t value)
{
	data_register_ = (uint16_t)((value << 2) | 1);
	output_.bits_remaining_until_empty = 9;
}

uint8_t Tape::get_data_register()
{
	return (uint8_t)(data_register_ >> 2);
}

void Tape::process_input_pulse(Storage::Tape::Tape::Pulse pulse)
{
	crossings_[0] = crossings_[1];
	crossings_[1] = crossings_[2];
	crossings_[2] = crossings_[3];

	crossings_[3] = Tape::Unrecognised;
	if(pulse.type != Storage::Tape::Tape::Pulse::Zero)
	{
		float pulse_length = (float)pulse.length.length / (float)pulse.length.clock_rate;
		if(pulse_length >= 0.35 / 2400.0 && pulse_length < 0.7 / 2400.0) crossings_[3] = Tape::Short;
		if(pulse_length >= 0.35 / 1200.0 && pulse_length < 0.7 / 1200.0) crossings_[3] = Tape::Long;
	}

	if(crossings_[0] == Tape::Long && crossings_[1] == Tape::Long)
	{
		push_tape_bit(0);
		crossings_[0] = crossings_[1] = Tape::Recognised;
	}
	else
	{
		if(crossings_[0] == Tape::Short && crossings_[1] == Tape::Short && crossings_[2] == Tape::Short && crossings_[3] == Tape::Short)
		{
			push_tape_bit(1);
			crossings_[0] = crossings_[1] =
			crossings_[2] = crossings_[3] = Tape::Recognised;
		}
	}
}

void Tape::run_for_cycles(unsigned int number_of_cycles)
{
	if(is_enabled_)
	{
		if(is_in_input_mode_)
		{
			if(is_running_)
			{
				TapePlayer::run_for_cycles((int)number_of_cycles);
			}
		}
		else
		{
			output_.cycles_into_pulse += number_of_cycles;
			while(output_.cycles_into_pulse > 1664)		// 1664 = the closest you can get to 1200 baud if you're looking for something
			{											// that divides the 125,000Hz clock that the sound divider runs off.
				output_.cycles_into_pulse -= 1664;
				push_tape_bit(1);
			}
		}
	}
}