ISCET Digital Electronics Principles 4 — Questions and Answers
Question 1: In a Karnaugh map, what do adjacent cells that are grouped together share?
- The same output value and differ in only one variable (Correct answer)
- Identical minterms
- The same sum-of-products form
- All variables in common
Correct answer: The same output value and differ in only one variable
Adjacent K-map cells differ in exactly one variable, allowing that variable to be eliminated when grouping for simplification.
Question 2: Which type of ROM can be erased by exposure to ultraviolet light?
- PROM
- EEPROM
- EPROM (Correct answer)
- Mask ROM
Correct answer: EPROM
EPROM (Erasable Programmable ROM) is erased by exposing its quartz window to UV light for several minutes.
Question 3: A multiplexer (MUX) with 4 select lines can route how many input channels?
- 4
- 8
- 16 (Correct answer)
- 32
Correct answer: 16
A MUX with n select lines supports 2ⁿ inputs; 4 select lines → 2⁴ = 16 input channels.
Question 4: What is propagation delay in a logic gate?
- Time for the output to settle after an input change (Correct answer)
- The gate's noise immunity threshold
- The setup time of a flip-flop
- The frequency of the clock signal
Correct answer: Time for the output to settle after an input change
Propagation delay (tpd) is the time interval between a change at the input and the resulting change at the output of a gate.
Question 5: Which Boolean identity is known as the 'absorption' law?
- A + A = A
- A + AB = A (Correct answer)
- A · 1 = A
- A + 0 = A
Correct answer: A + AB = A
The absorption law states A + AB = A, because A already 'absorbs' the term AB.
Question 6: In a shift register, what happens to the data bits on each clock pulse?
- Each bit moves one position in the direction of shift (Correct answer)
- All bits are cleared to zero
- Bits toggle their state
- Data is written in parallel to all stages
Correct answer: Each bit moves one position in the direction of shift
A shift register moves (shifts) each stored bit one position left or right with each active clock edge.
Question 7: What is the hexadecimal representation of decimal 255?
- EF
- FE
- FF (Correct answer)
- F0
Correct answer: FF
255₁₀ = 15×16¹ + 15×16⁰ = FF₁₆, since F represents 15 in hex.
ISCET Digital Electronics Principles 4
In a Karnaugh map, what do adjacent cells that are grouped together share?