8051 register-to-accumulator move Which 8051 instruction correctly moves the contents of register R3 into the accumulator A?
Digital Electronics
The 8051 Microcontroller
Difficulty: Easy
Choose an option
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AMOV 3R, A
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BMOV R3, A
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CMOV A, R3
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DMOV A, 3R
Answer
Correct Answer: MOV A, R3
Explanation
Introduction / Context:Understanding 8051 operand order and register names is essential. The MOV instruction uses the syntax MOV destination, source.
Given Data / Assumptions:
- Registers R0–R7 are general-purpose registers in the current bank.
- The accumulator is named A.
- MOV transfers a byte from source to destination.
Concept / Approach:To move R3 into A, R3 must be the source and A the destination: MOV A, R3. Variants like MOV R3, A reverse the direction; other shown mnemonics are invalid.
Step-by-Step Solution:
1) Identify destination: A.2) Identify source: R3.3) Apply syntax: MOV A, R3.4) Execute: A receives the byte from R3; flags typically unchanged.Verification / Alternative check:Consult the 8051 instruction set summary; MOV A, Rn is the documented form.
Why Other Options Are Wrong:
- MOV R3, A: Moves A into R3, opposite direction.
- MOV 3R, A / MOV A, 3R: Invalid operand naming.
Common Pitfalls:Reversing source/destination order or misnaming R3 as 3R.
Final Answer:MOV A, R3