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112 lines
3.0 KiB
C++
112 lines
3.0 KiB
C++
//
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// DiskDrive.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 14/07/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#ifndef DiskDrive_hpp
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#define DiskDrive_hpp
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#include "Disk.hpp"
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#include "DigitalPhaseLockedLoop.hpp"
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#include "../TimedEventLoop.hpp"
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namespace Storage {
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/*!
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Provides the shell for emulating a disk drive — something that takes a disk and has a drive head
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that steps between tracks, using a phase locked loop ('PLL') to decode a bit stream from the surface of
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the disk.
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Partly abstract; it is expected that subclasses will provide methods to deal with receiving a newly-recognised
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bit from the PLL and with crossing the index hole.
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TODO: double sided disks, communication of head size and permissible stepping extents, appropriate
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simulation of gain.
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*/
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class DiskDrive: public DigitalPhaseLockedLoop::Delegate, public TimedEventLoop {
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public:
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/*!
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Constructs a @c DiskDrive that will be run at @c clock_rate and runs its PLL at @c clock_rate*clock_rate_multiplier,
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spinning inserted disks at @c revolutions_per_minute.
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*/
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DiskDrive(unsigned int clock_rate, unsigned int clock_rate_multiplier, unsigned int revolutions_per_minute);
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/*!
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Communicates to the PLL the expected length of a bit.
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*/
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void set_expected_bit_length(Time bit_length);
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/*!
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Inserts @c disk into the drive.
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*/
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void set_disk(std::shared_ptr<Disk> disk);
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/*!
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@returns @c true if a disk is currently inserted; @c false otherwise.
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*/
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bool has_disk();
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/*!
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Advances the drive by @c number_of_cycles cycles.
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*/
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void run_for_cycles(int number_of_cycles);
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/*!
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@returns @c true if the drive head is currently at track zero; @c false otherwise.
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*/
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bool get_is_track_zero();
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/*!
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Steps the disk head the specified number of tracks. Positive numbers step inwards, negative numbers
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step outwards.
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*/
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void step(int direction);
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/*!
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Enables or disables the disk motor.
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*/
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void set_motor_on(bool motor_on);
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// to satisfy DigitalPhaseLockedLoop::Delegate
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void digital_phase_locked_loop_output_bit(int value);
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protected:
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/*!
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Should be implemented by subclasses; communicates each bit that the PLL recognises, also specifying
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the amount of time since the index hole was last seen.
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*/
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virtual void process_input_bit(int value, unsigned int cycles_since_index_hole) = 0;
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/*!
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Should be implemented by subcalsses; communicates that the index hole has been reached.
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*/
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virtual void process_index_hole() = 0;
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// for TimedEventLoop
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virtual void process_next_event();
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private:
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Time _bit_length;
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unsigned int _clock_rate;
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unsigned int _clock_rate_multiplier;
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Time _rotational_multiplier;
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std::shared_ptr<DigitalPhaseLockedLoop> _pll;
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std::shared_ptr<Disk> _disk;
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std::shared_ptr<Track> _track;
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int _head_position;
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unsigned int _cycles_since_index_hole;
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void set_track(Time initial_offset);
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inline void get_next_event();
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Track::Event _current_event;
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Time _time_into_track;
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};
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}
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#endif /* DiskDrive_hpp */
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