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962275c22a
It doesn't have one in real life, and now can live off the time counting that occurs on the SCSI bus.
105 lines
3.1 KiB
C++
105 lines
3.1 KiB
C++
//
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// SCSI.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 12/08/2019.
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// Copyright © 2019 Thomas Harte. All rights reserved.
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//
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#include "SCSI.hpp"
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using namespace SCSI;
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Bus::Bus(HalfCycles clock_rate) {
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cycles_to_time_ = 1.0 / double(clock_rate.as_int());
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// NB: note that the dispatch times below are **ORDERED**
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// from least to greatest. Each box should contain the number
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// of whole clock periods it will take to get the the first
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// discrete moment after the required delay interval has been met.
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dispatch_times_[0] = 1 + int(CableSkew / cycles_to_time_);
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dispatch_times_[1] = 1 + int(DeskewDelay / cycles_to_time_);
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dispatch_times_[2] = 1 + int(BusFreeDelay / cycles_to_time_);
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dispatch_times_[3] = 1 + int(BusSettleDelay / cycles_to_time_);
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dispatch_times_[4] = 1 + int(BusClearDelay / cycles_to_time_);
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dispatch_times_[5] = 1 + int(BusSetDelay / cycles_to_time_);
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dispatch_times_[6] = 1 + int(ArbitrationDelay / cycles_to_time_);
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dispatch_times_[7] = 1 + int(ResetHoldTime / cycles_to_time_);
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}
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size_t Bus::add_device() {
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const auto slot = device_states_.size();
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device_states_.push_back(DefaultBusState);
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return slot;
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}
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void Bus::set_device_output(size_t device, BusState output) {
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if(device_states_[device] == output) return;
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device_states_[device] = output;
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const auto previous_state = state_;
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state_ = DefaultBusState;
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for(auto state: device_states_) {
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state_ |= state;
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}
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if(state_ == previous_state) return;
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// printf("SCSI bus: %02x %c%c%c%c%c%c%c%c%c%c\n",
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// state_ & 0xff,
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// (state_ & Line::Parity) ? 'p' : '-',
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// (state_ & Line::SelectTarget) ? 's' : '-',
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// (state_ & Line::Attention) ? 't' : '-',
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// (state_ & Line::Control) ? 'c' : '-',
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// (state_ & Line::Busy) ? 'b' : '-',
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// (state_ & Line::Acknowledge) ? 'a' : '-',
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// (state_ & Line::Reset) ? 'r' : '-',
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// (state_ & Line::Input) ? 'i' : '-',
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// (state_ & Line::Message) ? 'm' : '-',
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// (state_ & Line::Request) ? 'q' : '-'
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// );
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bool was_asleep = preferred_clocking() == ClockingHint::Preference::None;
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dispatch_index_ = 0;
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time_in_state_ = HalfCycles(0);
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if(was_asleep) update_clocking_observer();
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}
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BusState Bus::get_state() {
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return state_;
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}
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void Bus::add_observer(Observer *observer) {
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observers_.push_back(observer);
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}
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ClockingHint::Preference Bus::preferred_clocking() {
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return (dispatch_index_ < dispatch_times_.size()) ? ClockingHint::Preference::RealTime : ClockingHint::Preference::None;
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}
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void Bus::update_observers() {
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const auto time_elapsed = double(time_in_state_.as_int()) * cycles_to_time_;
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for(auto &observer: observers_) {
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observer->scsi_bus_did_change(this, state_, time_elapsed);
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}
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}
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void Bus::run_for(HalfCycles time) {
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if(dispatch_index_ < dispatch_times_.size()) {
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time_in_state_ += time;
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const auto old_index = dispatch_index_;
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const auto time_as_int = time_in_state_.as_int();
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while(time_as_int >= dispatch_times_[dispatch_index_] && dispatch_index_ < dispatch_times_.size()) {
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++dispatch_index_;
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}
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if(dispatch_index_ != old_index) {
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update_observers();
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}
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if(preferred_clocking() == ClockingHint::Preference::None) {
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update_clocking_observer();
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}
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}
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}
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