Question

In The Following VHDL Process, A, B, C, And D Are All Integers That Have A Value Of 0 At Time = 10 Ns. If E Changes From '0' To '1' At Time 20 Ns, Specify The Time At Which Each Signal Will Change And The Value To Which It Will Change.

p1: procces begin
A ← 1 after 15 ns;
B ← A + 1
C ← B + 1 after 10ns;
D ← B + 2 after 3ns;
A ← A + 5 after 15ns;
B ← B + 7
end process p1;

(Hint: Where No Delay Is Mentioned, Assume 'Delta' Delay And Remember That All Statements In A Process Are Sequential But

Answer 1

The VHDL process specifies signal assignments for the variables A, B, C, and D. At specific times, these signals change to different values. The times and values of each signal change are summarized. When E changes, it doesn't affect any of the other signals.

Step-by-step explanation:

The VHDL process mentioned in the question specifies a series of signal assignments for the variables A, B, C, and D. The process starts at time 0 and each signal assignment occurs sequentially. Let's analyze the time at which each signal will change and the value it will change to:

1. A: A will change from 0 to 1 at time 15 ns.
2. B: B is assigned the value of A+1, so B will also change from 0 to 1 at time 15 ns.
3. C: C is assigned the value of B+1 and the assignment has a delay of 10 ns. So C will change from 0 to 2 at time 25 ns.
4. D: D is assigned the value of B+2 with a delay of 3 ns. So D will change from 0 to 3 at time 18 ns.
5. A: A is assigned the value of A+5 with a delay of 15 ns. Since the previous assignment to A was at time 15 ns, A will change from 1 to 6 at time 30 ns.
6. B: B is assigned the value of B+7 without any delay. So B will change from 1 to 8 at time 30 ns.

The times and values of each signal change are summarized as follows:

• A: 15 ns - 1, 30 ns - 6
• B: 15 ns - 1, 30 ns - 8
• C: 25 ns - 2
• D: 18 ns - 3

When E changes from '0' to '1' at time 20 ns, it doesn't affect any of the signals mentioned in the process.