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90 lines
2.1 KiB
C++
90 lines
2.1 KiB
C++
//
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// SCSI.hpp
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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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#ifndef SCSI_hpp
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#define SCSI_hpp
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#include <limits>
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#include <vector>
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namespace SCSI {
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typedef int BusState;
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static const BusState DefaultBusState = 0;
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/*!
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SCSI bus state is encoded entirely within an int.
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Bits correlate mostly but not exactly to the real SCSI bus.
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TODO: validate levels below. The bus uses open collector logic,
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so active low needs to be respected.
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*/
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enum Line: BusState {
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/// Provides the value currently on the data lines.
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Data = 0xff,
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/// Parity of the data lines.
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Parity = 1 << 8,
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/// Set if the SEL line is currently selecting a target.
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/// Reset if it is selecting an initiator.
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SelectTarget = 1 << 9,
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/// Set to indicate an attention condition. Reset otherwise.
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Attention = 1 << 10,
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/// Set if control is on the bus. Reset if data is on the bus.
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Control = 1 << 11,
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/// Set if the bus is busy. Reset otherwise.
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Busy = 1 << 12,
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/// Set if acknowledging a data transfer request. Reset otherwise.
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Acknowledge = 1 << 13,
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/// Set if a bus reset is being requested. Reset otherwise.
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Reset = 1 << 14,
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/// Set if data is currently an input to the initiator. Reset if it is an output.
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Input = 1 << 15,
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/// Set during the message phase. Reset otherwise.
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Message = 1 << 16,
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/// Set if requesting a data transfer. Reset otherwise.
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Request = 1 << 17,
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};
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class Bus {
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public:
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/*!
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Adds a device to the bus, returning the index it should use
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to refer to itself in subsequent calls to set_device_output.
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*/
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size_t add_device();
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/*!
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Sets the current output for @c device.
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*/
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void set_device_output(size_t device, BusState output);
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/*!
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@returns the current state of the bus.
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*/
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BusState get_state();
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struct Observer {
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virtual void scsi_bus_did_change(Bus *, BusState new_state) = 0;
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};
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/*!
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Adds an observer.
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*/
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void add_observer(Observer *);
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private:
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std::vector<BusState> device_states_;
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BusState state_ = DefaultBusState;
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std::vector<Observer *> observers_;
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};
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}
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#endif /* SCSI_hpp */
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