Table of Contents
What happens if a signal is missing from the sensitivity list during synthesis?
If they are not included in the sensitivity list, then that will result in your output not changing even when that input signal changes. This is a common error (due to carelessness).
What happens when a process neither has sensitivity list nor a wait statement?
Explanation: A process can be sensitive to one or more signals. These signals are either specified in the sensitivity list of the process. If there is no sensitivity list, then the signals used in WAIT statements are the signals to which process is sensitive. 8.
What does sensitivity list include?
The sensitivity list is where you list all the signals that you want to cause the code in the process to be evaluated whenever it changes state. For example, clock or master reset is often used in a sensitivity list. Whenever the reset or clock changes state, the code inside the process is executed.
What happens if we don’t write anything inside an always block?
If there are no timing control statements within an always block, the simulation will hang because of a zero-delay infinite loop. For example, always block attempts to invert the value of the signal clk. The statement is executed after every 0-time units.
What happened in the simulation if there is a sensitivity list and a wait statement are present within a process?
Explanation: The sensitivity list and wait statements can’t be used simultaneously in the same process. One can either use sensitive list or wait statements in a process. Both of them are used to define the signals to which the process is sensitive. These sensitive signals execute process as an infinite loop.
How does the sensitivity list work for always block?
The sensitivity list brings along a certain sense of timing i.e. whenever any signal in the sensitivity list changes, the always block is triggered. If there are no timing control statments within an always block, the simulation will hang because of a zero-delay infinite loop !
What happened in the simulation if there is sensitivity list and a wait statement?
A sensitivity list is an implicit wait statement. When a process have a sensitivity list it always suspends after executing the last sequential statement and then the signals that have been assign new values are updated. The wait statement provides an alternative form for suspending a process.
What happened in the simulation if there is sensitivity list and wait statement are present within a process?
Why we need to include all the input signals in the sensitivity list of the process?
Why we need to include all the input signals in the sensitivity list of the process? Explanation: If the input signals are not in the sensitivity list of the process, then one can’t monitor the change in input. Any change in input signal will not change the output simultaneously by running the process again. 3.
What is a sensitivity list why is it important?
You should always use a sensitivity list to trigger processes in production modules. Sensitivity lists are parameters to a process which lists all the signals that the process is sensitive to. If any of the signals change, the process will wake up, and the code within it is executed.
Why always blocks are not allowed in program block?
As part of the integration with SystemVerilog, the program was turned into a module-like construct with ports and initial blocks are now used to start the test procedure. Because an always block never terminates, it was kept out of the program block so the concept of test termination would still be there.
What could happen if a variable is not assigned in all possible executions in an always statement?
If you don’t assign every element that can be assigned inside an always@( * ) block every time that always@( * ) block is executed, a latch (similar to a register but much harder to work with in FPGAs) will be inferred for that element. This is never what you want and is a terrible place for bugs.