申論題

Problem 9 (15 points) Consider the 4-bit (i.e., A[3:0]) up-down counter in Fig. 3. Given the following signals:
 (i) initial begin CLK=1;#5 forever CLK=~CLK; end.
(ii) initial fork #10 Reset _6=0;#20 Reset b=1; join.
(iii) initial fork Down=O; Up =0; #40 UP=1; #150 Down= 1, #200 UP=0; #250 Down=0；join. Plot and explain the responses including, CLK, Reset b, Down, Up, and A[3:0] for a total of 300ns.