Processes InterviewQuestions - vineethkumarv/SystemVerilog_Course GitHub Wiki

1.Difference between fork_join,fork_join_any and fork_join_none ?

fork_join	fork_join_any	fok_join_none
In fork_join the main(parent) threads will execute after all the threads(child threads) in the fork_join is executed	In fork_join_any the main(parent) threads executes if any one of the child threads excecutes	In fork_join_none child threads and main(parent) threads are executed parallely

2.Can we use wait_fork in fork_join ?

We know that in fork_join the main thread is executed only when all the threads in fork_join is executed so here no need of using wait_fork. We can use wait fork after the fork_join_any or fork_join_none statement to wait for all the threads in the fork-join_any or fork_join_none to complete. So here in fork_join wait_fork is not required.

3.Difference between Blocking and Non-Blocking Assignments ?

blocking	Non-Blocking
In Blocking Assignment one statement is executed then the next statement will executed i.e first expression of right hand side is evaluated and immediately assigned to the left hand side variable	In Non-Blocking assignment evaluated all the right hand side expression for the current time unit and assigned to left-hand side variable at the end of the time unit
Represented by " = "	Represented by " <= "
It executes sequentially	It executes parallely
Blocking is used in combinational	Non-Blocking is used in sequential

4.Difference between wait event and @ event ?

If we triggered wait and @ in the same delay then wait statement is executed because the wait catches fast then @ event.

Example:

module tb;  
  event e;  
 initial begin  
        #20 ->e;  
        $display($time,"thread1");  
        end  
  initial   
    begin  
     #20 @e;  
     $display($time,"thread2");  
    end  
  initial   
   begin  
   #20 wait(e.triggered);  
   $display($time,"thread3");  
   end 
endmodule   

In the above example we can see that we have same delay for the event,wait and @ but after executing the event wait is executed eventhough we declared '@' in between, its because wait catches the fast then the @ so as a output we can only see thread1 and thread3.

5.Can we execute wait and @ with different delays ?

module tb;    
    event e;  
    initial begin  
    #20 ->e;  
   $display($time,"thread1");  
   end  
  initial   
    begin  
     #25 @e;  
     $display($time,"thread2");  
    end  
  initial   
   begin  
   #15 wait(e.triggered);  
   $display($time,"thread3");  
   end 
endmodule  

In the above example we can see that delays are different for event ,wait and @.We can also see that here @ delay is more than the event delay and wait delay is less than the event delay so here it executes only the wait statement with the event delay.So in the below figure we can see that thread 1 and thread 3 is executed with same delay(#20)