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121 lines
3.2 KiB
C++
121 lines
3.2 KiB
C++
//
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// Shifter.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 24/09/2017.
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// Copyright 2017 Thomas Harte. All rights reserved.
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//
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#include "Shifter.hpp"
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#include "Constants.hpp"
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using namespace Storage::Encodings::MFM;
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Shifter::Shifter() : owned_crc_generator_(new CRC::CCITT()), crc_generator_(owned_crc_generator_.get()) {}
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Shifter::Shifter(CRC::CCITT *crc_generator) : crc_generator_(crc_generator) {}
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void Shifter::set_is_double_density(bool is_double_density) {
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is_double_density_ = is_double_density;
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if(!is_double_density) is_awaiting_marker_value_ = false;
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}
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void Shifter::set_should_obey_syncs(bool should_obey_syncs) {
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should_obey_syncs_ = should_obey_syncs;
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}
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void Shifter::add_input_bit(int value) {
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shift_register_ = (shift_register_ << 1) | static_cast<unsigned int>(value);
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bits_since_token_++;
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token_ = Token::None;
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if(should_obey_syncs_) {
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if(!is_double_density_) {
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switch(shift_register_ & 0xffff) {
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case Storage::Encodings::MFM::FMIndexAddressMark:
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token_ = Token::Index;
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crc_generator_->reset();
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crc_generator_->add(Storage::Encodings::MFM::IndexAddressByte);
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break;
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case Storage::Encodings::MFM::FMIDAddressMark:
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token_ = Token::ID;
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crc_generator_->reset();
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crc_generator_->add(Storage::Encodings::MFM::IDAddressByte);
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break;
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case Storage::Encodings::MFM::FMDataAddressMark:
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token_ = Token::Data;
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crc_generator_->reset();
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crc_generator_->add(Storage::Encodings::MFM::DataAddressByte);
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break;
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case Storage::Encodings::MFM::FMDeletedDataAddressMark:
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token_ = Token::DeletedData;
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crc_generator_->reset();
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crc_generator_->add(Storage::Encodings::MFM::DeletedDataAddressByte);
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break;
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default:
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break;
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}
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} else {
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switch(shift_register_ & 0xffff) {
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case Storage::Encodings::MFM::MFMIndexSync:
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bits_since_token_ = 0;
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is_awaiting_marker_value_ = true;
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token_ = Token::Sync;
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break;
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case Storage::Encodings::MFM::MFMSync:
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bits_since_token_ = 0;
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is_awaiting_marker_value_ = true;
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crc_generator_->set_value(Storage::Encodings::MFM::MFMPostSyncCRCValue);
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token_ = Token::Sync;
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break;
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default:
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break;
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}
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}
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if(token_ != Token::None) {
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bits_since_token_ = 0;
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return;
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}
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}
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if(bits_since_token_ == 16) {
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token_ = Token::Byte;
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bits_since_token_ = 0;
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if(is_awaiting_marker_value_ && is_double_density_) {
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is_awaiting_marker_value_ = false;
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switch(get_byte()) {
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case Storage::Encodings::MFM::IndexAddressByte:
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token_ = Token::Index;
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break;
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case Storage::Encodings::MFM::IDAddressByte:
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token_ = Token::ID;
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break;
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case Storage::Encodings::MFM::DataAddressByte:
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token_ = Token::Data;
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break;
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case Storage::Encodings::MFM::DeletedDataAddressByte:
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token_ = Token::DeletedData;
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break;
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default: break;
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}
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}
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crc_generator_->add(get_byte());
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}
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}
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uint8_t Shifter::get_byte() const {
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return static_cast<uint8_t>(
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((shift_register_ & 0x0001) >> 0) |
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((shift_register_ & 0x0004) >> 1) |
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((shift_register_ & 0x0010) >> 2) |
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((shift_register_ & 0x0040) >> 3) |
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((shift_register_ & 0x0100) >> 4) |
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((shift_register_ & 0x0400) >> 5) |
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((shift_register_ & 0x1000) >> 6) |
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((shift_register_ & 0x4000) >> 7));
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}
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