mirror of
https://github.com/TomHarte/CLK.git
synced 2024-11-03 08:05:40 +00:00
152 lines
4.6 KiB
C++
152 lines
4.6 KiB
C++
//
|
|
// SCSI.hpp
|
|
// Clock Signal
|
|
//
|
|
// Created by Thomas Harte on 12/08/2019.
|
|
// Copyright © 2019 Thomas Harte. All rights reserved.
|
|
//
|
|
|
|
#ifndef SCSI_hpp
|
|
#define SCSI_hpp
|
|
|
|
#include <array>
|
|
#include <limits>
|
|
#include <vector>
|
|
|
|
#include "../../../ClockReceiver/ClockReceiver.hpp"
|
|
#include "../../../ClockReceiver/ClockingHintSource.hpp"
|
|
|
|
namespace SCSI {
|
|
|
|
typedef int BusState;
|
|
|
|
static const BusState DefaultBusState = 0;
|
|
|
|
/*!
|
|
SCSI bus state is encoded entirely within an int.
|
|
Bits correlate mostly but not exactly to the real SCSI bus.
|
|
|
|
TODO: validate levels below. The bus uses open collector logic,
|
|
so active low needs to be respected.
|
|
*/
|
|
enum Line: BusState {
|
|
/// Provides the value currently on the data lines.
|
|
Data = 0xff,
|
|
/// Parity of the data lines.
|
|
Parity = 1 << 8,
|
|
/// Set if the SEL line is currently selecting a target.
|
|
/// Reset if it is selecting an initiator.
|
|
SelectTarget = 1 << 9,
|
|
/// Set to indicate an attention condition. Reset otherwise.
|
|
Attention = 1 << 10,
|
|
/// Set if control is on the bus. Reset if data is on the bus.
|
|
Control = 1 << 11,
|
|
/// Set if the bus is busy. Reset otherwise.
|
|
Busy = 1 << 12,
|
|
/// Set if acknowledging a data transfer request. Reset otherwise.
|
|
Acknowledge = 1 << 13,
|
|
/// Set if a bus reset is being requested. Reset otherwise.
|
|
Reset = 1 << 14,
|
|
/// Set if data is currently an input to the initiator. Reset if it is an output.
|
|
Input = 1 << 15,
|
|
/// Set during the message phase. Reset otherwise.
|
|
Message = 1 << 16,
|
|
/// Set if requesting a data transfer. Reset otherwise.
|
|
Request = 1 << 17,
|
|
};
|
|
|
|
#define us(x) (x) / 1000000.0
|
|
#define ns(x) (x) / 1000000000.0
|
|
|
|
/// The minimum amount of time that reset must be held for.
|
|
constexpr double ResetHoldTime = us(25.0);
|
|
|
|
/// The minimum amount of time a SCSI device must wait after asserting ::Busy
|
|
/// until the data bus can be inspected to see whether arbitration has been won.
|
|
constexpr double ArbitrationDelay = us(1.7);
|
|
|
|
/// The maximum amount of time a SCSI device can take from a detection that the
|
|
/// bus is free until it asserts ::Busy and its ID for the purposes of arbitration.
|
|
constexpr double BusSetDelay = us(1.1);
|
|
|
|
/// The maximum amount of time a SCSI device is permitted to take to stop driving
|
|
/// all bus signals after: (i) the release of ::Busy ushering in a bus free phase;
|
|
/// or (ii) some other device has asserted ::Select during an arbitration phase.
|
|
constexpr double BusClearDelay = ns(650.0);
|
|
|
|
/// The minimum amount of time to wait for the bus to settle after changing
|
|
/// "certain control signals". TODO: which?
|
|
constexpr double BusSettleDelay = ns(450.0);
|
|
|
|
/// The minimum amount of time a SCSI must wait from detecting that the bus is free
|
|
/// and asserting ::Busy if starting an arbitration phase.
|
|
constexpr double BusFreeDelay = ns(100.0);
|
|
|
|
/// The minimum amount of time required for deskew of "certain signals". TODO: which?
|
|
constexpr double DeskewDelay = ns(45.0);
|
|
|
|
/// The maximum amount of time that propagation of a SCSI bus signal can take between
|
|
/// any two devices.
|
|
constexpr double CableSkew = ns(10.0);
|
|
|
|
#undef ns
|
|
#undef us
|
|
|
|
class Bus: public ClockingHint::Source {
|
|
public:
|
|
Bus(HalfCycles clock_rate);
|
|
|
|
/*!
|
|
Adds a device to the bus, returning the index it should use
|
|
to refer to itself in subsequent calls to set_device_output.
|
|
*/
|
|
size_t add_device();
|
|
|
|
/*!
|
|
Sets the current output for @c device.
|
|
*/
|
|
void set_device_output(size_t device, BusState output);
|
|
|
|
/*!
|
|
@returns the current state of the bus.
|
|
*/
|
|
BusState get_state();
|
|
|
|
struct Observer {
|
|
/// Reports to an observer that the bus changed from a previous state to @c new_state,
|
|
/// along with the time since that change was observed. The time is in seconds, and is
|
|
/// intended for comparison with the various constants defined at namespace scope:
|
|
/// ArbitrationDelay et al. Observers will be notified each time one of the thresholds
|
|
/// defined by those constants is crossed.
|
|
virtual void scsi_bus_did_change(Bus *, BusState new_state, double time_since_change) = 0;
|
|
};
|
|
/*!
|
|
Adds an observer.
|
|
*/
|
|
void add_observer(Observer *);
|
|
|
|
/*!
|
|
SCSI buses don't have a clock. But devices on the bus are concerned with time-based factors,
|
|
and `run_for` is the way that time propagates within this emulator. So please permit this
|
|
fiction.
|
|
*/
|
|
void run_for(HalfCycles);
|
|
|
|
/// As per ClockingHint::Source.
|
|
ClockingHint::Preference preferred_clocking() final;
|
|
|
|
private:
|
|
HalfCycles time_in_state_;
|
|
double cycles_to_time_ = 1.0;
|
|
size_t dispatch_index_ = 0;
|
|
std::array<int, 8> dispatch_times_;
|
|
|
|
std::vector<BusState> device_states_;
|
|
BusState state_ = DefaultBusState;
|
|
std::vector<Observer *> observers_;
|
|
};
|
|
|
|
}
|
|
|
|
#endif /* SCSI_hpp */
|