CLK/Components/5380/ncr5380.hpp

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

#ifndef ncr5380_hpp
#define ncr5380_hpp

#include <cstdint>

#include "../../Storage/MassStorage/SCSI/SCSI.hpp"
#include "../../Storage/MassStorage/SCSI/DirectAccessDevice.hpp"
#include "../../ClockReceiver/ClockReceiver.hpp"
#include "../../ClockReceiver/ClockingHintSource.hpp"


namespace NCR {
namespace NCR5380 {

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

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

		/*! Reads from @c address. */
		uint8_t read(int address);

		/*!
			As per its design manual:

				"The NCR 5380 is a clockless device. Delays such as bus
				free delay, bus set delay and bus settle delay are
				implemented using gate delays."

			Therefore this fictitious implementation of an NCR5380 needs
			a way to track time even though the real one doesn't take in
			a clock. This is provided by `run_for`.

			Nevertheless, the clocking doesn't need to be very precise.
			Please provide a clock that is close to 200,000 Hz.
		*/
		void run_for(Cycles);

		/// As per ClockingHint::Source.
		ClockingHint::Preference preferred_clocking() final;

	private:
		// TEMPORARY. For development expediency, the 5380 owns its own
		// SCSI bus and target. These will be moved out.
		SCSI::Bus bus_;
		SCSI::Target::Target<SCSI::DirectAccessDevice> device_;

		const int clock_rate_;
		size_t device_id_;

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

		enum class ExecutionState {
			None,

			WatchingBusy,
			PerformingDMA,
		} state_ = ExecutionState::None;
		int time_in_state_ = 0;
		bool lost_arbitration_ = false, arbitration_in_progress_ = false;

		void set_execution_state(ExecutionState state);
};

}
}

#endif /* ncr5380_hpp */