hades.models.flipflops
Class LatchMetastable

java.lang.Object
  hades.simulator.SimObject
      hades.models.flipflops.GenericFlipflop
          hades.models.flipflops.LatchMetastable

All Implemented Interfaces:

Assignable, java.lang.Cloneable, ContextToolTip, java.io.Serializable, Simulatable

public class LatchMetastable

extends GenericFlipflop

implements Simulatable, java.io.Serializable

LatchMetastable: a level-sensitive metastable D-latch

This class models a simple level-sensistive D-type metastable latch. Unlike class Latch, this simulation component will never generate 'X' or 'U' values at its outputs. Instead, random '0' or '1' values will be generated at initialization or whenever the value of the flipflop becomes undefined, e.g. due to a hazard condition.

Note that the delay for the propagation of this random value is random, too, with a delay of up to fifty times the usual flipflop propagation delay, t_pass.

Signals are expected to be StdLogic1164 objects.

See Also:

Serialized Form

Field Summary

Fields inherited from class hades.models.flipflops.GenericFlipflop

port_NQ, port_Q, t_hold, t_pass, t_setup

Fields inherited from class hades.simulator.SimObject

classloader, console, debug, editor, name, parent, ports, propertySheet, simulator, symbol, versionId, visible

Constructor Summary

LatchMetastable()

Method Summary

void	elaborate(java.lang.Object arg) elaborate: store a reference to our simulator, then call evaluate() to set a random 0/1 initial state for this latch.
void	evaluate(java.lang.Object arg) evaluate: check the C and D inputs and calculate Q and NQ.
int	getRandom01Value() get a random 0 or 1 value, with probability 0.5 each.
double	getRandomDelay() get a random propagation delay time in the range 0 ..

Methods inherited from class hades.models.flipflops.GenericFlipflop

assign, configure, getDelay, getHoldTime, getSetupTime, getToolTip, initialize, scheduleEvent, scheduleEventAfter, scheduleOutputValue, scheduleOutputValueAfter, setDelay, setDelay, setHoldTime, setHoldTime, setSetupTime, setSetupTime, write

Methods inherited from class hades.simulator.SimObject

constructDynamicSymbol, copy, getBindkey, getClassLoader, getDebug, getEditor, getExternalResources, getFullName, getName, getParent, getPort, getPorts, getPropertySheet, getResourceAsStream, getSimulator, getSymbol, getSymbolResourceName, getVersionId, isVisible, keyPressed, message, mousePressed, needsDynamicSymbol, needsExternalResources, setClassLoader, setConsole, setDebug, setEditor, setName, setParent, setPorts, setSimulator, setSymbol, setVersionId, setVisible, tearDown, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface hades.simulator.Simulatable

message

Constructor Detail

LatchMetastable

public LatchMetastable()

Method Detail

elaborate

public void elaborate(java.lang.Object arg)

elaborate: store a reference to our simulator, then call evaluate() to set a random 0/1 initial state for this latch.

Specified by:

elaborate in interface Simulatable

Overrides:

elaborate in class GenericFlipflop

evaluate

public void evaluate(java.lang.Object arg)

evaluate: check the C and D inputs and calculate Q and NQ. If either input is undefined or a timing violation is detected, the latch enters a random 0/1 state after an also random delay (which may be much larger than the usual latch propagation delay).

Specified by:

evaluate in interface Simulatable

Overrides:

evaluate in class SimObject

Parameters:

arg - an arbitrary object argument

getRandom01Value

public int getRandom01Value()

get a random 0 or 1 value, with probability 0.5 each.

getRandomDelay

public double getRandomDelay()

get a random propagation delay time in the range 0 .. 50*t_pass.