Microprocessors Questions and Answers – 8051 Instruction Set -2

This set of Microprocessors Questions and Answers for Aptitude test focuses on “8051 Instruction Set -2”.

1. 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
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2. 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
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3. The third byte of the long jump instruction is
a) opcode
b) 5 LSBs of opcode
c) higher byte of jump location or subroutine
d) lower byte of jump location or subroutine
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4. 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
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5. 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
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6. Which of the following is not an unconditional control transfer instruction?
a) JMP
b) RET
c) JNC
d) CALL
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7. The conditional control transfer instructions use
a) status flags
b) bits of bit addressable RAM
c) SFRs termed bit
d) all of the mentioned
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8. Which of the following is not a conditional control transfer instruction?
a) JC
b) JBC
c) JNC
d) NONE
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9. 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
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10. The mnemonic, JNB is used to jump to the specified relative address only if
a) specified bit=1
b) specified bit=0
c) specified bit is non-recursive
d) none
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11. The type of operand that is not allowed to use in boolean instructions of 8051 is
a) direct register operands
b) indirect register operands
c) immediate bit
d) none
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12. In boolean instructions, the flag that is the only allowed destination operand for two operand instructions is
a) overflow flag
b) underflow flag
c) auxiliary flag
d) carry flag
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