CLK/Components/5380/ncr5380.hpp

//
//  ncr5380.hpp
//  Clock Signal
//
//  Created by Thomas Harte on 10/08/2019.
//  Copyright © 2019 Thomas Harte. All rights reserved.
//

#pragma once

#include <cstdint>

#include "../../Storage/MassStorage/SCSI/SCSI.hpp"


namespace NCR::NCR5380 {

/*!
	Models the NCR 5380, a SCSI interface chip.
*/
class NCR5380 final: public SCSI::Bus::Observer {
public:
	NCR5380(SCSI::Bus &, int clock_rate);

	/*! Writes @c value to @c address. */
	void write(int address, uint8_t value, bool dma_acknowledge = false);

	/*! Reads from @c address. */
	uint8_t read(int address, bool dma_acknowledge = false);

	/*! @returns The SCSI ID assigned to this device. */
	size_t scsi_id();

	/*! @return @c true if DMA request is active; @c false otherwise. */
	bool dma_request();

	/*! Signals DMA acknowledge with a simultaneous read. */
	uint8_t dma_acknowledge();

	/*! Signals DMA acknowledge with a simultaneous write. */
	void dma_acknowledge(uint8_t);

private:
	SCSI::Bus &bus_;

	const int clock_rate_;
	size_t device_id_;

	SCSI::BusState bus_output_ = SCSI::DefaultBusState;
	SCSI::BusState expected_phase_ = SCSI::DefaultBusState;
	uint8_t mode_ = 0xff;
	uint8_t initiator_command_ = 0xff;
	uint8_t data_bus_ = 0xff;
	uint8_t target_command_ = 0xff;
	bool test_mode_ = false;
	bool assert_data_bus_ = false;
	bool dma_request_ = false;
	bool dma_acknowledge_ = false;
	bool end_of_dma_ = false;

	bool irq_ = false;
	bool phase_mismatch_ = false;

	enum class ExecutionState {
		None,
		WaitingForBusy,
		WatchingBusy,
		PerformingDMA,
	} state_ = ExecutionState::None;
	enum class DMAOperation {
		Ready,
		Send,
		TargetReceive,
		InitiatorReceive
	} dma_operation_ = DMAOperation::Ready;
	bool lost_arbitration_ = false, arbitration_in_progress_ = false;

	void set_execution_state(ExecutionState state);

	SCSI::BusState target_output() const;
	void update_control_output();

	void scsi_bus_did_change(SCSI::Bus *, SCSI::BusState new_state, double time_since_change) final;
	bool phase_matches() const;
};

}