– Inertial delay
– Transport delay
– Delta delay
Inertial Delay
• Inertial delay is the default in VHDL.
• Behaves similarly to the actual device.
• Output signal of the device has inertia, which must be overcome for the signal to change value.
• The inertial delay model is by far the most commonly used in all currently available simulators.
Transport Delay
• It represents a wire delay in which any pulse, no matter how small, is propagated to the output signal delayed by the delay value specified.
• Especially useful for modeling delay line devices, wire delays on a PCB, and path delays on an ASIC.
Delta delay
• These are used since the PC that processes and simulates a concurrent phenomenon is basically a sequential machine.
• The simulation program mimics concurrency by scheduling events in some order.
• Simulation deltas are used to order some types of events during a simulation.
• Specifically, zero delay events must be ordered to produce consistent results.
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