250+ TOP MCQs on Addressing Modes of 8051 and Answers

Microprocessor Multiple Choice Questions on “Addressing Modes of 8051”.

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1. Which of the following is not an addressing mode of 8051?
a) register instructions
b) register specific instructions
c) indexed addressing
d) none
Answer: d
Clarification: The six addressing modes of 8051 are
1. Direct addressing
2. Indirect addressing
3. Register instructions
4. Register specific(Register Implicit) instructions
5. Immediate mode
6. Indexed addressing.

2. The symbol, ‘addr 16’ represents the 16-bit address which is used by the instructions to specify the
a) destination address of CALL
b) source address of JUMP
c) destination address of call or jump
d) source address of call or jump
Answer: c
Clarification: The symbol, ‘addr 16’ represents the 16-bit destination address which is used by the LCALL or LJMP instruction to specify the call or jump destination address, within 64 Kbytes program memory.

3. The storage of addresses that can be directly accessed is
a) external data RAM
b) internal data ROM
c) internal data RAM and SFRS
d) external data ROM and SFRS
Answer: c
Clarification: Only internal data RAM and SFRS can be directly addressed in direct addressing mode.

4. The address register for storing the 16-bit addresses can only be
a) stack pointer
b) data pointer
c) instruction register
d) accumulator
Answer: b
Clarification: The address register for storing the 16-bit addresses can only be data pointer.

5. The address register for storing the 8-bit addresses can be
a) R0 of the selected bank of register
b) R1 of the selected bank of register
c) Stack pointer
d) All of the mentioned
Answer: d
Clarification: The registers R0 and R1 of the selected bank of registers or stack pointer can be used as address registers for storing the 8-bit addresses.

6. The instruction, ADD A, R7 is an example of
a) register instructions
b) register specific instructions
c) indexed addressing
d) none
Answer: a
Clarification: In register instructions addressing mode, operands are stored in the registers R0-R7 of the selected register bank. One of these registers is specified in the instruction.

7. The addressing mode, in which the instructions has no source and destination operands is
a) register instructions
b) register specific instructions
c) direct addressing
d) indirect addressing
Answer: b
Clarification: In register specific instructions addressing mode, the instructions don’t have source and destination operands. Some of the instructions always operate only on a specific register.

8. The instruction, RLA performs
a) rotation of address register to left
b) rotation of accumulator to left
c) rotation of address register to right
d) rotation of accumulator to right
Answer: b
Clarification: The instruction, RLA rotates accumulator left.

9. The instruction, ADD A, #100 performs
a) 100(decimal) is added to contents of address register
b) 100(decimal) is subtracted from the accumulator
c) 100(decimal) is added to contents of an accumulator
d) none
Answer: c
Clarification: Immediate data 100(decimal) is added to the contents of the accumulator.

10. In which of these addressing modes, a constant is specified in the instruction, after the opcode byte?
a) register instructions
b) register specific instructions
c) direct addressing
d) immediate mode
Answer: d
Clarification: In immediate mode, an immediate data, i.e. a constant is specified in the instruction, after the opcode byte.

11. The only memory which can be accessed using indexed addressing mode is
a) RAM
b) ROM
c) Main memory
d) Program memory
Answer: d
Clarification: Only program memory can be accessed using the indexed addressing mode.

12. The data address of look-up table is found by adding the contents of
a) accumulator with that of program counter
b) accumulator with that of program counter or data pointer
c) data register with that of program counter or accumulator
d) data register with that of program counter or data pointer
Answer: b
Clarification: The look-up table data address is found out by adding the contents of register accumulator with that of the program counter or data pointer.

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