8051 instruction semantics — does 'RL A' rotate the eight bits of the Accumulator left by one position? State whether the mnemonic RL A performs a one-bit left rotate confined to A (bit7 wraps to bit0, carry flag unchanged).

Introduction / Context:The 8051 family provides two left-rotate instructions for the Accumulator: RL A and RLC A. Understanding the difference is essential for bit-level operations, look-up indexing, and simple arithmetic without disturbing the carry flag.

Given Data / Assumptions:

• Target CPU: 8051/8052 architecture
• Mnemonic under discussion: RL A
• Accumulator A is 8 bits wide (A7…A0)
• Carry flag CY exists in PSW but may or may not be affected depending on the instruction

Concept / Approach:RL A performs a pure 8-bit rotate left within A. Bit7 moves into bit0, and all other bits shift left by one. The carry flag is not used and not updated. In contrast, RLC A rotates through the carry: bit7 goes to CY and CY enters bit0.

Step-by-Step Solution:

Verification / Alternative check:Examine the flags after RL A; CY remains whatever it was. After RLC A, CY reflects previous b7. This confirms that RL does not use the carry path.

Why Other Options Are Wrong:

• False: contradicts the ISA definition.
• Only if CY = 1: CY is irrelevant for RL.
• Rotates through carry: that describes RLC, not RL.
• Shifts left filling 0: that would be a logical shift, not a rotate.

Common Pitfalls:

• Confusing RL with RLC and assuming CY always participates.
• Expecting CY to capture bit7 on RL; it does not.

Final Answer:True