8051 Instruction Set Questions

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11.

In logical instructions, the immediate data can be an operand for

A

increment operation

B

decrement operation

C

single operand instruction

D

none

Correct Answer: D

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12.

If the most significant bit of relative address byte is 1, then the short jump instruction is

A

forward jump

B

back jump

C

either forward or back jump

D

none

Correct Answer: B

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13.

The first byte of an absolute jump instruction consists of

A

3 LSBs of opcode and 5 MSBs of 11-bit address

B

5 MSBs of opcode and 3 LSBs of 11-bit address

C

6 MSBs of opcode and 1 LSB of 11-bit address

D

5 LSBs of opcode and 3 MSBs of 11-bit address

Correct Answer: D

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14.

The third byte of the long jump instruction is

A

opcode

B

5 LSBs of opcode

C

5 LSBs of opcode

D

lower byte of jump location or subroutine

Correct Answer: C

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15.

The absolute jump instruction is intended mainly for a jump within a memory space of

A

2 bytes

B

2 Kbytes

C

2 Mbytes

D

none

Correct Answer: B

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16.

The LJMP instruction is very useful in programming in the external code memory space of

A

32 MB

B

64 MB

C

32 KB

D

64 KB

Correct Answer: D

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17.

Which of the following is not an unconditional control transfer instruction?

A

JMP

B

RET

C

JNC

D

CALL

Correct Answer: C

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18.

The conditional control transfer instructions use

A

status flags

B

bits of bit addressable RAM

C

SFRs termed bit

D

all of the mentioned

Correct Answer: D

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19.

Which of the following is not a conditional control transfer instruction?

A

JC

B

JBC

C

JNC

D

NONE

Correct Answer: D

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20.

The mnemonic used to perform a subtraction of source with an 8-bit data and jumps to specified relative address if subtraction is non-zero is

A

DJNZ

B

CJNE

C

JZ

D

JNC

Correct Answer: B

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