Switching Circuits and Logic Design: Week 11: Assignment 11:

1. Which of the following is true for an asynchronous sequential circuit?

 a. The speed of the circuit depends on the delay of the flip-flops.

 b. The speed of the circuit depends on the gate delays.

 c. The number of flip-flops required is same as that for a synchronous sequential circuit.

 d. None of these.

Ans: b

2. If an asynchronous sequential circuit has 4 primary inputs and 3 delay elements in the feedback back, the number of total states will be ………

Ans: 128

3. When do you say that an asynchronous sequential circuit has reached a stable state?

 a. All the inputs of the delay elements have appeared on the outputs of the delay elements.

 b. At least one of the inputs of the delay elements have appeared on the outputs of the delay elements.

 c. The inputs of the delay elements have stabilized.

 d. None of these.

Ans: a

4. Which of the following constitutes a static hazard?

 a. The output goes to 0, then temporarily moves to 1, and then again back to 0.

 b. The output goes to 0, then temporarily moves to 1 and 0, and then to 1.

 c. The output goes to 1, then temporarily moves to 0, and then again back to 1.

 d. None of these.

Ans:a,c

5. Which of the following constitutes a dynamic hazard?

 a. The output goes to 0, then temporarily moves to 1 and 0, before stabilizing to 1.

 b. The output goes to 0, then temporarily moves to 1, and then again back to 0.

 c. The output goes to 1, then temporarily moves to 0, and then again back to 1.

 d. None of these.

Ans:a

6. To make the 2-level realization of the function F = A’B + AC free from static-1 logic hazard, what should you do?

 a. Implement the function in multi-level form.

 b. Add a product term BC to F, and implement accordingly.

 c. Add a product term B’C to F, and implement accordingly.

 d. None of these.

Ans: b

7. Which other minterms will be contained in the transition cube [0100, 0010]?

 a. 0000 and 0110

 b. 1100 and 0011

 c. 0000 and 1100

 d. 0110 and 1100

Ans:a

8. How can you avoid a static-0 logic hazard in a circuit?

 a. By adding a product term corresponding to the transition cube in the Karnaugh map.

 b. Avoid any product term containing both a variable and its complement.

 c. Always have a 2-level realization.

 d. None of these.

Ans:b

9. What are the three basic elements in an ASM chart?

 a. State Box, Decision Box, Output Box

 b. State Box, Decision Box, Input Box

 c. Input Box, Output Box, State Box

 d. None of these.

Ans:d

10. While converting a FSM state diagram to an ASM chart, which of the following is true?

 a. Every FSM state will map into an ASM Block.

 b. Every FSM state will map into a State Box.

 c. Every FSM transition will map into a Decision Box.

 d. None of these.

Ans:a