Contents
What is maximum delay?
The maximum delay constraint limits the number of consecutive gates on the critical path of a high-speed circuit, because a high clock frequency means a short clock period.
What is combinational logic delay?
Combinational logic is characterized by its propagation delay and contamination delay. The propagation delay tpd is the maximum time from when an input changes until the output or outputs reach their final value. In response, Y changes some time later.
Why is combinational logic important?
Combinational logic is used in computer circuits to perform Boolean algebra on input signals and on stored data. Practical design of combinational logic systems may require consideration of the finite time required for practical logical elements to react to changes in their inputs.
How do you calculate maximum propagation delay?
Propagation delay is equal to d / s where d is the distance and s is the wave propagation speed. In wireless communication, s=c, i.e. the speed of light.
Which is the maximum propagation delay in combinational logic?
Combinational logic is characterized by its propagation delay and contamination delay. The propagation delay tpd is the maximum time from when an input changes until the output or outputs reach their final value. The contamination delay tcd is the minimum time from when an input changes until any output starts to change its value.
What is the propagation delay of a circuit?
The propagation delay of a signal path is the time it takes between the change in input and the change in output for that signal. If not managed properly, propagation delays can result in logic circuits that run too slowly to meet their requirements, or that fail altogether.
When does a circuit have a min delay?
In contrast, circuits also have min-delay constraints that memory element inputs must not change until a hold time after the sampling edge. If these constraints are violated, the circuit may sample the output while it is changing, leading to incorrect results.
Why are Max delay and min delay constraints innocuous?
The max-delay constraints set the performance of the system, but are relatively innocuous because if they are violated, the circuit can still be made to function correctly by reducing the clock frequency. In contrast, circuits also have min-delay constraints that memory element inputs must not change until a hold time after the sampling edge.