/// <summary>
/// The main execution cycle of the Spectrum VM
/// </summary>
/// <param name="token">Cancellation token</param>
/// <param name="options">Execution options</param>
/// <return>True, if the cycle completed; false, if it has been cancelled</return>
public bool ExecuteCycle(CancellationToken token, ExecuteCycleOptions options)
{
ExecuteCycleOptions = options;
ExecutionCompletionReason = ExecutionCompletionReason.None;
LastExecutionStartTact = Cpu.Tacts;
LastExecutionContentionValue = ContentionAccumulated;
// --- We use these variables to calculate wait time at the end of the frame
var cycleStartTime = Clock.GetCounter();
var cycleStartTact = Cpu.Tacts;
var cycleFrameCount = 0;
// --- We use this variable to check whether to stop in Debug mode
var executedInstructionCount = -1;
// --- Loop #1: The main cycle that goes on until cancelled
while (!token.IsCancellationRequested)
{
if (_frameCompleted)
{
// --- This counter helps us to calculate where we are in the frame after
// --- each CPU operation cycle
LastFrameStartCpuTick = Cpu.Tacts - Overflow;
// --- Notify devices to start a new frame
OnNewFrame();
LastRenderedUlaTact = Overflow;
_frameCompleted = false;
}
// --- Loop #2: The physical frame cycle that goes on while CPU and ULA
// --- processes everything whithin a physical frame (0.019968 second)
while (!_frameCompleted)
{
// --- Check for leaving maskable interrupt mode
if (RunsInMaskableInterrupt)
{
if (Cpu.Registers.PC == 0x0052)
{
// --- We leave the maskable interrupt mode when the
// --- current instruction completes
RunsInMaskableInterrupt = false;
}
}
// --- Check debug mode when a CPU instruction has been entirelly executed
if (!Cpu.IsInOpExecution)
{
// --- Check for cancellation
if (token.IsCancellationRequested)
{
ExecutionCompletionReason = ExecutionCompletionReason.Cancelled;
return(false);
}
// --- The next instruction is about to be executed
executedInstructionCount++;
// --- Check for timeout
if (options.TimeoutTacts > 0 &&
cycleStartTact + options.TimeoutTacts < Cpu.Tacts)
{
ExecutionCompletionReason = ExecutionCompletionReason.Timeout;
return(false);
}
// --- Check for reaching the termination point
if (options.EmulationMode == EmulationMode.UntilExecutionPoint)
{
if (options.TerminationPoint < 0x4000)
{
// --- ROM & address must match
if (options.TerminationRom == MemoryDevice.GetSelectedRomIndex() &&
options.TerminationPoint == Cpu.Registers.PC)
{
// --- We reached the termination point within ROM
ExecutionCompletionReason = ExecutionCompletionReason.TerminationPointReached;
return(true);
}
}
else if (options.TerminationPoint == Cpu.Registers.PC)
{
// --- We reached the termination point within RAM
ExecutionCompletionReason = ExecutionCompletionReason.TerminationPointReached;
return(true);
}
}
// --- Check for entering maskable interrupt mode
if (Cpu.MaskableInterruptModeEntered)
{
RunsInMaskableInterrupt = true;
}
// --- Check for a debugging stop point
if (options.EmulationMode == EmulationMode.Debugger)
{
if (IsDebugStop(options, executedInstructionCount))
{
// --- At this point, the cycle should be stopped because of debugging reasons
// --- The screen should be refreshed
ScreenDevice.OnFrameCompleted();
ExecutionCompletionReason = ExecutionCompletionReason.BreakpointReached;
return(true);
}
}
}
// --- Check for interrupt signal generation
InterruptDevice.CheckForInterrupt(CurrentFrameTact);
// --- Run a single Z80 instruction
Cpu.ExecuteCpuCycle();
_lastBreakpoint = null;
// --- Run a rendering cycle according to the current CPU tact count
var lastTact = CurrentFrameTact;
ScreenDevice.RenderScreen(LastRenderedUlaTact + 1, lastTact);
LastRenderedUlaTact = lastTact;
// --- Exit if the emulation mode specifies so
if (options.EmulationMode == EmulationMode.UntilHalt &&
(Cpu.StateFlags & Z80StateFlags.Halted) != 0)
{
ExecutionCompletionReason = ExecutionCompletionReason.Halted;
return(true);
}
// --- Notify each CPU-bound device that the current operation has been completed
foreach (var device in _cpuBoundDevices)
{
device.OnCpuOperationCompleted();
}
// --- Decide whether this frame has been completed
_frameCompleted = !Cpu.IsInOpExecution && CurrentFrameTact >= _frameTacts;
} // -- End Loop #2
// --- A physical frame has just been completed. Take care about screen refresh
cycleFrameCount++;
FrameCount++;
// --- Notify devices that the current frame completed
OnFrameCompleted();
// --- Exit if the emulation mode specifies so
if (options.EmulationMode == EmulationMode.UntilFrameEnds)
{
ExecutionCompletionReason = ExecutionCompletionReason.FrameCompleted;
return(true);
}
// --- Wait while the frame time ellapses
if (!ExecuteCycleOptions.FastVmMode)
{
var nextFrameCounter = cycleStartTime + cycleFrameCount * PhysicalFrameClockCount;
Clock.WaitUntil((long)nextFrameCounter, token);
}
// --- Start a new frame and carry on
Overflow = CurrentFrameTact % _frameTacts;
} // --- End Loop #1
// --- The cycle has been interrupted by cancellation
ExecutionCompletionReason = ExecutionCompletionReason.Cancelled;
return(false);
}
/// <summary>
/// The main execution cycle of the Spectrum VM
/// </summary>
/// <param name="token">Cancellation token</param>
/// <param name="options">Execution options</param>
/// <param name="completeOnCpuFrame">The cycle should complete on CPU frame completion</param>
/// <return>True, if the cycle completed; false, if it has been cancelled</return>
public bool ExecuteCycle(CancellationToken token, ExecuteCycleOptions options, bool completeOnCpuFrame = false)
{
ExecuteCycleOptions = options;
ExecutionCompletionReason = ExecutionCompletionReason.None;
LastExecutionStartTact = Cpu.Tacts;
// --- We use this variables to check whether to stop in Debug mode
var executedInstructionCount = -1;
var entryStepOutDepth = Cpu.StackDebugSupport.StepOutStackDepth;
// --- Check if we're just start running the next frame
if (HasFrameCompleted)
{
// --- This counter helps us to calculate where we are in the frame after
// --- each CPU operation cycle
LastFrameStartCpuTick = Cpu.Tacts - Overflow;
// --- Notify devices to start a new frame
OnNewFrame();
LastRenderedUlaTact = Overflow;
HasFrameCompleted = false;
}
// --- The physical frame cycle that goes on while CPU and ULA
// --- processes everything within a physical frame (0.019968 second)
while (!HasFrameCompleted)
{
// --- Check debug mode when a CPU instruction has been entirely executed
if (!Cpu.IsInOpExecution)
{
// --- The next instruction is about to be executed
executedInstructionCount++;
// --- Check for cancellation
if (token.IsCancellationRequested)
{
ExecutionCompletionReason = ExecutionCompletionReason.Cancelled;
return(false);
}
// --- Check for CPU frame completion
if (completeOnCpuFrame && Cpu.Tacts > LastExecutionStartTact + CPU_FRAME)
{
ExecutionCompletionReason = ExecutionCompletionReason.CpuFrameCompleted;
return(true);
}
// --- Check for several termination modes
switch (options.EmulationMode)
{
// --- Check for reaching the termination point
case EmulationMode.UntilExecutionPoint when options.TerminationPoint < 0x4000:
{
// --- ROM & address must match
if (options.TerminationRom == MemoryDevice.GetSelectedRomIndex() &&
options.TerminationPoint == Cpu.Registers.PC)
{
// --- We reached the termination point within ROM
ExecutionCompletionReason = ExecutionCompletionReason.TerminationPointReached;
return(true);
}
break;
}
// --- Check if we reached the termination point within RAM
case EmulationMode.UntilExecutionPoint
when options.TerminationPoint == Cpu.Registers.PC:
ExecutionCompletionReason = ExecutionCompletionReason.TerminationPointReached;
return(true);
// --- Check for a debugging stop point
case EmulationMode.Debugger
when IsDebugStop(options, executedInstructionCount, entryStepOutDepth) &&
DebugConditionSatisfied():
// --- At this point, the cycle should be stopped because of debugging reasons
// --- The screen should be refreshed
ExecutionCompletionReason = ExecutionCompletionReason.BreakpointReached;
return(true);
}
}
// --- Check for interrupt signal generation
InterruptDevice.CheckForInterrupt(CurrentFrameTact);
// --- Run a single Z80 instruction
Cpu.ExecuteCpuCycle();
_lastBreakpoint = null;
// --- Run a rendering cycle according to the current CPU tact count
var lastTact = CurrentFrameTact;
ScreenDevice.RenderScreen(LastRenderedUlaTact + 1, lastTact);
LastRenderedUlaTact = lastTact;
// --- Exit if the CPU is HALTed and the emulation mode specifies so
if (options.EmulationMode == EmulationMode.UntilHalt &&
(Cpu.StateFlags & Z80StateFlags.Halted) != 0)
{
ExecutionCompletionReason = ExecutionCompletionReason.Halted;
return(true);
}
// --- Notify each CPU-bound device that the current operation has been completed
foreach (var device in _cpuBoundDevices)
{
device.OnCpuOperationCompleted();
}
// --- Decide whether this frame has been completed
HasFrameCompleted = !Cpu.IsInOpExecution && CurrentFrameTact >= FrameTacts;
}
// --- A physical frame has just been completed. Take care about screen refresh
FrameCount++;
Overflow = CurrentFrameTact % FrameTacts;
// --- Notify devices that the current frame completed
OnFrameCompleted();
// --- We exit the cycle when the render frame has completed
ExecutionCompletionReason = ExecutionCompletionReason.RenderFrameCompleted;
return(true);
}