8051 Microcontroller MCQ [Free PDF] – 9 Objective Questions with Answers

8051 Architecture (1)

Q1Easy

Asked in: GPSC DEE Electrical · DEE Master paper · 2026

Consider the following statements regarding 8051 architecture:
1. It is an 8-bit microcontroller.
2. It has Harvard architecture.
3. It has separate program and data memory spaces.
Which of the above statements is/are correct?

View answer & solution

Correct answer: D. 1, 2 and 3

Quick explanation

The classic 8051 is an 8-bit Harvard-style microcontroller with separate code and data spaces. The standard core has 4 KB on-chip program ROM and 128 bytes internal RAM, supports external memory, multiple interrupts and configurable interrupt priority. Key relation: Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Exam focus: Remember 07H for stack pointer reset. Common trap: 00H is not the reset value of the 8051 stack pointer.

Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Verified · SRO editorial deskSolution page → Report

ADC Interfacing (1)

Q2Easy

Asked in: GPSC DEE Electrical · DEE Master paper · 2026

Consider the following statements regarding ADC interfacing to 8051:
1. ADC converts analog signal to digital.
2. Start of conversion signal is required.
3. End of conversion signal indicates completion.
Which of the above statements is/are correct?

View answer & solution

Correct answer: B. 1, 2 and 3

Quick explanation

An n-bit ADC divides its input range into roughly 2^n quantization levels. Quantization error is inherent in finite resolution, while sampling frequency determines whether the signal can be reconstructed without aliasing. Key relation: LSB≈V_FS/2^n; ideal quantization error ≈±0.5 LSB.

Exam focus: More bits improve amplitude resolution; higher sample rate improves time/frequency representation. Common trap: Resolution is not simply 1/n and sampling rate is not irrelevant.

LSB≈VFS/2^n; ideal quantization error ≈±0.5 LSB.

Verified · SRO editorial deskSolution page → Report

Addressing Modes (1)

Q3Easy

Asked in: GPSC DEE Electrical · DEE Master paper · 2026

Consider the following statements regarding 8051 Addressing modes:
1. Immediate addressing includes operand in instruction.
2. Direct addressing uses memory address explicitly.
3. Indirect addressing uses register to hold address.
Which of the above statements is/are correct?

View answer & solution

Correct answer: D. 1, 2 and 3

Quick explanation

The classic 8051 is an 8-bit Harvard-style microcontroller with separate code and data spaces. The standard core has 4 KB on-chip program ROM and 128 bytes internal RAM, supports external memory, multiple interrupts and configurable interrupt priority. Key relation: Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Exam focus: Remember 07H for stack pointer reset. Common trap: 00H is not the reset value of the 8051 stack pointer.

Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Verified · SRO editorial deskSolution page → Report

CPU Registers (1)

Q4Easy

Asked in: GPSC DEE Electrical · DEE Master paper · 2026

Consider the following statements:
1. Accumulator is used for arithmetic and logic operations.
2. Program Counter holds the address of next instruction.
3. Stack Pointer points to 00H on reset in 8051 Microcontroller.
Which of the above statements is/are correct?

View answer & solution

Correct answer: A. 1 and 2 only

Quick explanation

The classic 8051 is an 8-bit Harvard-style microcontroller with separate code and data spaces. On reset the stack pointer is 07H, so the first PUSH stores at 08H. Key relation: Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Exam focus: Remember 07H for stack pointer reset. Common trap: 00H is not the reset value of the 8051 stack pointer.

Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Verified · SRO editorial deskSolution page → Report

Instruction Set (1)

Q5Easy

Asked in: GPSC DEE Electrical · DEE Master paper · 2026

Consider the following statements regarding 8051 instructions:
1. MOV instruction transfers data between registers/memory.
2. ADD instruction affects flags.
3. INC instruction affects carry flag.
Which of the above statements is/are correct?

View answer & solution

Correct answer: C. 1 and 2 only

Quick explanation

The classic 8051 is an 8-bit Harvard-style microcontroller with separate code and data spaces. The standard core has 4 KB on-chip program ROM and 128 bytes internal RAM, supports external memory, multiple interrupts and configurable interrupt priority. Key relation: Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Exam focus: Remember 07H for stack pointer reset. Common trap: 00H is not the reset value of the 8051 stack pointer.

Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Verified · SRO editorial deskSolution page → Report

Interrupts (1)

Q6Easy

Asked in: GPSC DEE Electrical · DEE Master paper · 2026

Consider the following statements regarding 8051 interfacing to peripherals:
1. 8051 supports multiple interrupt sources.
2. Interrupts can be enabled/disabled.
3. Interrupt priority can be configured.
Which of the above statements is/are correct?

View answer & solution

Correct answer: A. All of the above

Quick explanation

The classic 8051 is an 8-bit Harvard-style microcontroller with separate code and data spaces. The standard core has 4 KB on-chip program ROM and 128 bytes internal RAM, supports external memory, multiple interrupts and configurable interrupt priority. Key relation: Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Exam focus: Remember 07H for stack pointer reset. Common trap: 00H is not the reset value of the 8051 stack pointer.

Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Verified · SRO editorial deskSolution page → Report

Memory Architecture (1)

Q7Easy

Asked in: GPSC DEE Electrical · DEE Master paper · 2026

Consider the following statements regarding 8051 Architecture:
1. 8051 has 4KB on-chip program memory (standard version).
2. Internal RAM is 128 bytes.
3. External memory can be interfaced.
Which of the above statements is/are correct?

View answer & solution

Correct answer: A. All of the above

Quick explanation

The classic 8051 is an 8-bit Harvard-style microcontroller with separate code and data spaces. The standard core has 4 KB on-chip program ROM and 128 bytes internal RAM, supports external memory, multiple interrupts and configurable interrupt priority. Key relation: Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Exam focus: Remember 07H for stack pointer reset. Common trap: 00H is not the reset value of the 8051 stack pointer.

Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Verified · SRO editorial deskSolution page → Report

Memory Interfacing (1)

Q8Easy

Asked in: GPSC DEE Electrical · DEE Master paper · 2026

Consider the following statements regarding Memory interfacing in 8051:
1. Address decoding is required for memory interfacing.
2. Chip select signal is used to enable memory device.
3. Multiple devices can share data bus.
Which of the above statements is/are correct?

View answer & solution

Correct answer: B. 1, 2 and 3

Quick explanation

The classic 8051 is an 8-bit Harvard-style microcontroller with separate code and data spaces. The standard core has 4 KB on-chip program ROM and 128 bytes internal RAM, supports external memory, multiple interrupts and configurable interrupt priority. Key relation: Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Exam focus: Remember 07H for stack pointer reset. Common trap: 00H is not the reset value of the 8051 stack pointer.

Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Verified · SRO editorial deskSolution page → Report

Stack (1)

Q9Easy

Asked in: GPSC DEE Electrical · DEE Master paper · 2026

Consider the following statements regarding Stack in 8051:
1. Stack operates on LIFO principle.
2. PUSH increases stack pointer.
3. POP decreases stack pointer.
Which of the above statements is/are correct?

View answer & solution

Correct answer: D. 1, 2 and 3

Quick explanation

The classic 8051 is an 8-bit Harvard-style microcontroller with separate code and data spaces. On reset the stack pointer is 07H, so the first PUSH stores at 08H. Key relation: Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Exam focus: Remember 07H for stack pointer reset. Common trap: 00H is not the reset value of the 8051 stack pointer.

Reset SP=07H; classic internal RAM=128 bytes; standard ROM=4 KB.

Verified · SRO editorial deskSolution page → Report

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8051 Microcontroller MCQ [Free PDF] – 9 Objective Questions with Answers

8051 Architecture (1)

ADC Interfacing (1)

Addressing Modes (1)

CPU Registers (1)

Instruction Set (1)

Interrupts (1)

Memory Architecture (1)

Memory Interfacing (1)

Stack (1)