Logic simulation

Logic simulation is the use of simulation software to predict the behavior of digital circuits and hardware description languages. Simulation can be performed at varying degrees of physical abstraction, such as at the transistor level, gate level, register-transfer level (RTL), electronic system-level (ESL), or behavioral level. Logic simulation may be used as part of the verification process in designing hardware. Simulations have the advantage of providing a familiar look and feel to the user in that it is constructed from the same language and symbols used in design. By allowing the user to interact directly with the design, simulation is a natural way for the designer to get feedback on their design. The level of effort required to debug and then verify the design is proportional to the maturity of the design. That is, early in the design's life, bugs and incorrect behavior are usually found quickly. As the design matures, the simulation will require more time and resources to run, and errors will take progressively longer to be found. This is particularly problematic when simulating components for modern-day systems; every component that changes state in a single clock cycle on the simulation will require several clock cycles to simulate. A straightforward approach to this issue may be to emulate the circuit on a field-programmable gate array instead. Formal verification can also be explored as an alternative to simulation, although a formal proof is not always possible or convenient. A prospective way to accelerate logic simulation is using distributed and parallel computations. To help gauge the thoroughness of a simulation, tools exist for assessing code coverage, functional coverage, finite state machine (FSM) coverage, and many other metrics. Event simulation allows the design to contain simple timing information – the delay needed for a signal to travel from one place to another. During simulation, signal changes are tracked in the form of events. A change at a certain time triggers an event after a certain delay.