Difficulty: Easy
Correct Answer: copy the contents of memory whose address is in R1 to the accumulator
Explanation:
Introduction / Context:
Indirect addressing allows access to internal RAM using a register as a pointer. This question checks your understanding of the 8051 syntax @R1, which dereferences R1 to obtain the target byte.
Given Data / Assumptions:
Concept / Approach:
Dereferencing R1 provides a byte from internal data memory 0x00–0x7F (lower 128) or indirectly from 0x00–0xFF on variants; the byte is then moved into A. No flags are affected by the addressing mode itself.
Step-by-Step Solution:
Verification / Alternative check:
Compare with MOV @R1, A which writes A to the addressed memory, confirming the direction of transfer is reversed in that form.
Why Other Options Are Wrong:
Common Pitfalls:
Confusing register direct (R1) with register indirect (@R1) addressing, and mixing up source/destination order.
Final Answer:
copy the contents of memory whose address is in R1 to the accumulator
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