Package mars.simulator

Class Simulator

java.lang.Object

java.util.Observable

mars.simulator.Simulator

public class Simulator
extends Observable

Used to simulate the execution of an assembled MIPS program.

Version:

August 2005

Author:

Pete Sanderson

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	Simulator.StopListener

Field Summary

Fields

Modifier and Type	Field	Description
static int	BREAKPOINT	various reasons for simulate to end...
static int	CLIFF_TERMINATION
static int	EXCEPTION
static int	externalInterruptingDevice
static int	MAX_STEPS
static int	NO_DEVICE
static int	NORMAL_TERMINATION
static int	PAUSE_OR_STOP

Method Summary

Modifier and Type	Method	Description
void	addStopListener(Simulator.StopListener l)
static Simulator	getInstance()	Returns the Simulator object
static boolean	inDelaySlot()	Determine whether or not the next instruction to be executed is in a "delay slot".
void	removeStopListener(Simulator.StopListener l)
boolean	simulate(MIPSprogram p, int pc, int maxSteps, int[] breakPoints, AbstractAction actor)	Simulate execution of given MIPS program.
void	stopExecution(AbstractAction actor)	Set the volatile stop boolean variable checked by the execution thread at the end of each MIPS instruction execution.

Methods inherited from class java.util.Observable

addObserver, countObservers, deleteObserver, deleteObservers, hasChanged, notifyObservers, notifyObservers

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

NO_DEVICE

public static final int NO_DEVICE

See Also:

Constant Field Values

externalInterruptingDevice

public static volatile int externalInterruptingDevice

BREAKPOINT

public static final int BREAKPOINT

various reasons for simulate to end...

See Also:

Constant Field Values

EXCEPTION

public static final int EXCEPTION

See Also:

Constant Field Values

MAX_STEPS

public static final int MAX_STEPS

See Also:

Constant Field Values

NORMAL_TERMINATION

public static final int NORMAL_TERMINATION

See Also:

Constant Field Values

CLIFF_TERMINATION

public static final int CLIFF_TERMINATION

See Also:

Constant Field Values

PAUSE_OR_STOP

public static final int PAUSE_OR_STOP

See Also:

Constant Field Values

Method Details

getInstance

public static Simulator getInstance()

Returns the Simulator object

Returns:

the Simulator object in use

inDelaySlot

public static boolean inDelaySlot()

Determine whether or not the next instruction to be executed is in a "delay slot". This means delayed branching is enabled, the branch condition has evaluated true, and the next instruction executed will be the one following the branch. It is said to occupy the "delay slot." Normally programmers put a nop instruction here but it can be anything.

Returns:

true if next instruction is in delay slot, false otherwise.

simulate

public boolean simulate(MIPSprogram p,
 int pc,
 int maxSteps,
 int[] breakPoints,
 AbstractAction actor)
                 throws ProcessingException

Simulate execution of given MIPS program. It must have already been assembled.

Parameters:

p - The MIPSprogram to be simulated.

pc - address of first instruction to simulate; this goes into program counter

maxSteps - maximum number of steps to perform before returning false (0 or less means no max)

breakPoints - array of breakpoint program counter values, use null if none

actor - the GUI component responsible for this call, usually GO or STEP. null if none.

Returns:

true if execution completed, false otherwise

Throws:

ProcessingException - Throws exception if run-time exception occurs.

stopExecution

public void stopExecution(AbstractAction actor)

Set the volatile stop boolean variable checked by the execution thread at the end of each MIPS instruction execution. If variable is found to be true, the execution thread will depart gracefully so the main thread handling the GUI can take over. This is used by both STOP and PAUSE features.

addStopListener

public void addStopListener(Simulator.StopListener l)

removeStopListener

public void removeStopListener(Simulator.StopListener l)