DELAY MODELING

Delays are timing parameters given by the user for modeling physical characteristics of hardware.



Delays are specified in signal assignment statements only.

Delays should NOT be used in variable assignments.

INERTIAL DELAY

• It is used to model the inherent inertia of physical devices.

• Example:

– The input value must be stable for a specified minimum pulse duration before the value is allowed to propagate to the output.

– If the input is not stable for the specified limit, no output change occurs.

TRANSPORT DELAY

• It represents pure propagation delay i.e., wires and interconnect delays.

• Signal value is assigned with a specified delay independent of the width of the input waveform.

DELAYS




information shared by www.irvs.info

SIMULATION DELTA

• What is simulation delta?

• Several logic changes occur simultaneously in a circuit (concurrent operations)

• But simulator being run by a sequential machine, hence it cannot process events concurrently.

• To take care this, time is frozen within the simulator.

• The real time the simulator takes to complete all concurrent operations in the queue is called SIMULATION DELTA.



The minimum time interval possible for the simulator is assumed to be 1 ns here

• SUMMARY


Simulation deltas allow ordering of events that occur at the same simulation time during simulation.

Simulation deltas are infinitesimal amount of time used as synchronism mechanism when zero delay events are present.


information shared by www.irvs.info