8051 register-to-accumulator move Which 8051 instruction correctly moves the contents of register R3 into the accumulator A?

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:

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