Which of the following do not represent memory-reference instructions? A. mode…
2025
Which of the following do not represent memory-reference instructions?
A. mode = 1, opcode = 010
B. mode = 0, opcode = 111
C. mode = 1, opcode = 111
D. mode = 1, opcode = 110
E. mode = 1, opcode = 001
Choose the correct answer from the options given below.
- A.
B & C only
- B.
B & D only
- C.
A & D only
- D.
A & E only
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Correct answer: A
Correct answer: B & C only
In the basic-computer instruction format, memory-reference instructions use opcodes 000 through 110. Opcode 111 is reserved for non-memory-reference instruction classes.
B: mode = 0, opcode = 111 -> register-reference instruction, so it is not memory-reference.
C: mode = 1, opcode = 111 -> I/O-reference instruction, so it is not memory-reference.
A, D and E: opcodes 010, 110 and 001 are memory-reference opcodes.
Therefore, B and C are the instructions that do not represent memory-reference instructions.
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