CLK/Components/8530/z8530.hpp

//
//  z8530.hpp
//  Clock Signal
//
//  Created by Thomas Harte on 07/06/2019.
//  Copyright © 2019 Thomas Harte. All rights reserved.
//

#pragma once

#include <cstdint>

namespace Zilog::SCC {

/*!
	Models the Zilog 8530 SCC, a serial adaptor.
*/
class z8530 {
	public:
		/*
			**Interface for emulated machine.**

			Notes on addressing below:

			There's no inherent ordering of the two 'address' lines,
			A/B and C/D, but the methods below assume:

				A/B = A0
				C/D = A1
		*/

		/// Performs a read from the SCC; see above for conventions as to 'address'.
		std::uint8_t read(int address);
		/// Performs a write to the SCC; see above for conventions as to 'address'.
		void write(int address, std::uint8_t value);
		/// Resets the SCC.
		void reset();

		/// @returns The current value of the status output: @c true for active; @c false for inactive.
		bool get_interrupt_line() const;

		struct Delegate {
			/*!
				Communicates that @c scc now has the interrupt line status @c new_status.
			*/
			virtual void did_change_interrupt_status(z8530 *scc, bool new_status) = 0;
		};

		/*!
			Sets the delegate for this SCC. If this is a new delegate it is sent
			an immediate did_change_interrupt_status message, to get it
			up to speed.
		*/
		void set_delegate(Delegate *delegate) {
			if(delegate_ == delegate) return;
			delegate_ = delegate;
			delegate_->did_change_interrupt_status(this, get_interrupt_line());
		}

		/*
			**Interface for serial port input.**
		*/
		void set_dcd(int port, bool level);

	private:
		class Channel {
			public:
				uint8_t read(bool data, uint8_t pointer);
				void write(bool data, uint8_t pointer, uint8_t value);
				void set_dcd(bool level);
				bool get_interrupt_line() const;

			private:
				uint8_t data_ = 0xff;

				enum class Parity {
					Even, Odd, Off
				} parity_ = Parity::Off;

				enum class StopBits {
					Synchronous, OneBit, OneAndAHalfBits, TwoBits
				} stop_bits_ = StopBits::Synchronous;

				enum class Sync {
					Monosync, Bisync, SDLC, External
				} sync_mode_ = Sync::Monosync;

				int clock_rate_multiplier_ = 1;

				uint8_t interrupt_mask_ = 0;			// i.e. Write Register 0x1.

				uint8_t external_interrupt_mask_ = 0;	// i.e. Write Register 0xf.
				bool external_status_interrupt_ = false;
				uint8_t external_interrupt_status_ = 0;

				bool dcd_ = false;
		} channels_[2];

		uint8_t pointer_ = 0;

		uint8_t interrupt_vector_ = 0;

		uint8_t master_interrupt_control_ = 0;

		bool previous_interrupt_line_ = false;
		void update_delegate();
		Delegate *delegate_ = nullptr;
};

}