BEE Digital Logic and Design 4 — Questions and Answers
Question 1: A shift register has 4 stages. How many clock pulses are needed to serially load a 4-bit word?
- 1
- 2
- 4 (Correct answer)
- 8
Correct answer: 4
A serial-in shift register requires one clock pulse per bit, so 4 clock pulses are needed to load all 4 bits of a 4-bit word.
Question 2: Which canonical form expresses a Boolean function as a sum of minterms?
- Product of Maxterms (POM)
- Sum of Products (SOP) in standard form (Correct answer)
- Product of Sums (POS) in standard form
- Sum of Maxterms
Correct answer: Sum of Products (SOP) in standard form
The Sum of Minterms (canonical SOP) form expresses a Boolean function as an OR of minterms, each minterm being an AND of all variables in complemented or uncomplemented form.
Question 3: In a Moore state machine, the output depends on:
- Current state and current inputs
- Current inputs only
- Current state only (Correct answer)
- Next state and current inputs
Correct answer: Current state only
In a Moore machine, outputs are a function of the current state only, making them synchronous with the clock and independent of current inputs.
Question 4: What is the hexadecimal equivalent of the binary number 1011 1100?
- BA
- BC (Correct answer)
- CB
- AB
Correct answer: BC
Splitting 10111100 into nibbles: 1011=B and 1100=C, giving hexadecimal BC.
Question 5: Which multiplexer configuration can implement any 3-variable Boolean function without additional gates?
- 2-to-1 MUX
- 4-to-1 MUX
- 8-to-1 MUX (Correct answer)
- 16-to-1 MUX
Correct answer: 8-to-1 MUX
An 8-to-1 MUX with 3 select lines can directly implement any 3-variable Boolean function by connecting constants (0 or 1) to its data inputs.
Question 6: A T flip-flop has T=1 and Q=0 before the clock edge. What is Q after the active clock edge?
- 0
- 1 (Correct answer)
- Undefined
- Same as T
Correct answer: 1
When T=1, the T flip-flop toggles, so Q changes from 0 to 1 on the active clock edge.
Question 7: Which number system uses the digits 0–7 and a base of 8?
- Binary
- Decimal
- Octal (Correct answer)
- Hexadecimal
Correct answer: Octal
The octal number system uses base 8 with digits 0 through 7, and each octal digit corresponds to exactly 3 binary bits.
BEE Digital Logic and Design 4
A shift register has 4 stages.
How many clock pulses are needed to serially load a 4-bit word?