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99 lines
2.2 KiB
C++
99 lines
2.2 KiB
C++
//
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// Spectrum.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 07/03/2021.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#include "Spectrum.hpp"
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//
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// Source used for the logic below was primarily https://sinclair.wiki.zxnet.co.uk/wiki/Spectrum_tape_interface
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//
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using namespace Storage::Tape::ZXSpectrum;
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void Parser::process_pulse(const Storage::Tape::Tape::Pulse &pulse) {
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if(pulse.type == Storage::Tape::Tape::Pulse::Type::Zero) {
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push_wave(WaveType::Gap);
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return;
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}
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// Only pulse duration matters; the ZX Spectrum et al do not rely on polarity.
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const float t_states = pulse.length.get<float>() * 3'500'000.0f;
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// Too long => gap.
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if(t_states > 2400.0f) {
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push_wave(WaveType::Gap);
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return;
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}
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// 1940–2400 t-states => pilot.
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if(t_states > 1940.0f) {
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push_wave(WaveType::Pilot);
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return;
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}
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// 1282–1940 t-states => one.
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if(t_states > 1282.0f) {
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push_wave(WaveType::One);
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return;
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}
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// 895–1282 => zero.
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if(t_states > 795.0f) {
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push_wave(WaveType::Zero);
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return;
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}
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// 701–895 => sync 2.
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if(t_states > 701.0f) {
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push_wave(WaveType::Sync2);
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return;
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}
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// Anything remaining above 600 => sync 1.
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if(t_states > 600.0f) {
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push_wave(WaveType::Sync1);
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return;
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}
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// Whatever this was, it's too short. Call it a gap.
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push_wave(WaveType::Gap);
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}
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void Parser::inspect_waves(const std::vector<Storage::Tape::ZXSpectrum::WaveType> &waves) {
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switch(waves[0]) {
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// Gap and Pilot map directly.
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case WaveType::Gap: push_symbol(SymbolType::Gap, 1); break;
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case WaveType::Pilot: push_symbol(SymbolType::Pilot, 1); break;
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// Encountering a sync 2 on its own is unexpected.
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case WaveType::Sync2:
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push_symbol(SymbolType::Gap, 1);
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break;
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// A sync 1 should be followed by a sync 2 in order to make a sync.
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case WaveType::Sync1:
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if(waves.size() < 2) return;
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if(waves[1] == WaveType::Sync2) {
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push_symbol(SymbolType::Sync, 2);
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} else {
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push_symbol(SymbolType::Gap, 1);
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}
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break;
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// Both one and zero waves should come in pairs.
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case WaveType::One:
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case WaveType::Zero:
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if(waves.size() < 2) return;
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if(waves[1] == waves[0]) {
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push_symbol(waves[0] == WaveType::One ? SymbolType::One : SymbolType::Zero, 2);
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} else {
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push_symbol(SymbolType::Gap, 1);
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}
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break;
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}
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}
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