Cycle based simulation and event based simulation dating. Cycle-based simulation with decision diagrams | sciweavers
A change at a certain time triggers an event after a certain delay.
Due to these considerations, almost all commercial logic simulators have an event based capability, even if they primarily rely on cycle based techniques.
In these cases, since event simulation only simulates necessary events, performance may no longer be a disadvantage over cycle simulation.
Event simulation also has the advantage of greater flexibility, handling design features difficult to handle with cycle simulation, such as asynchronous logic and incommensurate clocks.
However, chip design trends point to event simulation gaining relative performance due to activity factor reduction in the circuit due to techniques such as clock gating and power gatingwhich are becoming much more commonly used in an effort to reduce power dissipation.
By allowing the user to interact directly with the design, simulation is a natural way for the designer to get feedback on their design. How fast an event simulation runs depends on the number of events to be processed the amount of activity in the model. A straightforward approach to this issue may be to emulate the circuit on a field-programmable gate array instead.
Event simulation versus cycle simulation[ edit ] Event simulation allows the design to contain simple timing information — the delay needed for a signal to travel from one place to another. In cycle simulation, it is not possible to specify delays.
Basic Difference between Event based simulator and Cycle based simulator
A prospective way to accelerate logic simulation is using distributed and parallel computations. Cycle simulation therefore runs at a constant speed, regardless of activity in the model. During simulation, signal changes are tracked in the form of events.
As the design matures, the simulation will require more time and resources to run, and errors will take progressively longer to be found. Formal verification can also be explored as an alternative to simulation, although a formal proof is not always possible or convenient.
Optimized implementations may take advantage of low model activity to speed up simulation by skipping evaluation of gates whose inputs didn't change. Events are sorted by the time when they will occur, and when all events for a particular time have been handled, the simulated time is advanced to the time of the next scheduled event.