ECE 351 Digital Systems Design
Sample Exam Questions
Note: these sample questions are only used to demonstrate the form of questions that may appear
in the exam. They may or may not relate to the actual questions in the exam in any way.
Sample Question 1: Design methodology
What’s the fundamental difference between the structural and behavioral design methodology?
Implement the following Boolean expression using both structural and behavioral designs to
illustrate such difference.
(𝐴 + 𝐵) ∙ (𝐶 + 𝐷)
Sample Question 2: VHDL Process Behavior
Consider the following VHDL code:
demo_process: process(A,B)
begin
if B=’1’ then
A <= 0;
else A<=1;
C <= A and B;
end process demo_process;
Suppose when this process is executed, the current values of A and B are both 1. After this process
finishes, what will be the value of C?
Sample Question 3: VHDL behavioral design
Design a finite state machine using VHDL behavioral design method to implement the following
functionality: counting the number of 1’s in the input bit streams. If the number of 1’s is odd, the
state machine sets its output to 1. Otherwise if the number of 1’s is even (including 0), the state
machine sets its output to 0.
Example system input and output:
Input: 1 0 0 0 1 0 1 0 1 1 1 0 0
Output: 1 1 1 1 0 0 1 1 0 1 0 0 0