BEE FREE BEE Bachelor of Electrical Engineering Digital Logic and Microprocessors Questions and Answers 2 — Questions and Answers
Question 1: What is the primary function of a multiplexer (MUX) in digital logic?
- Selects one of many inputs and forwards it to a single output (Correct answer)
- Converts analog signals to digital
- Stores data in flip-flops
- Amplifies digital signals
Correct answer: Selects one of many inputs and forwards it to a single output
A multiplexer selects one input from multiple sources based on select lines and routes it to a single output.
Question 2: In the 8085 microprocessor, which register pair is used as the default stack pointer?
- SP register (Correct answer)
- HL pair
- BC pair
- DE pair
Correct answer: SP register
The 8085 has a dedicated 16-bit Stack Pointer (SP) register that holds the address of the top of the stack.
Question 3: Which Boolean algebra theorem states that A + A·B = A?
- Absorption theorem (Correct answer)
- De Morgan's theorem
- Consensus theorem
- Idempotent theorem
Correct answer: Absorption theorem
The absorption theorem states that a variable ORed with its AND combination with another variable simplifies to just the original variable.
Question 4: What is the fan-out specification of a digital logic gate?
- The maximum number of gate inputs that the output can drive (Correct answer)
- The propagation delay of the gate
- The power consumption at maximum frequency
- The noise margin of the output
Correct answer: The maximum number of gate inputs that the output can drive
Fan-out specifies the maximum number of same-family gate inputs that an output can reliably drive while maintaining valid logic levels.
Question 5: Which addressing mode does the 8086 instruction MOV AX, [BX+SI+8] use?
- Based indexed with displacement (Correct answer)
- Direct addressing
- Register indirect
- Immediate addressing
Correct answer: Based indexed with displacement
This instruction uses the base register BX, index register SI, and an 8-bit displacement, combining all three into based indexed with displacement mode.
Question 6: What is the purpose of the carry look-ahead technique in adder circuits?
- To reduce propagation delay by computing carry signals in parallel (Correct answer)
- To increase the number of bits that can be added
- To reduce the number of gates required
- To simplify the circuit layout
Correct answer: To reduce propagation delay by computing carry signals in parallel
Carry look-ahead generates all carry bits simultaneously using dedicated logic, eliminating the ripple delay of sequential carry propagation.
BEE FREE BEE Bachelor of Electrical Engineering Digital Logic and Microprocessors Questions and Answers 2
What is the primary function of a multiplexer (MUX) in digital logic?