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SarkariResultOutAdditional Assistant Engineer (Electrical) · 2026

Previous Year Question

The instruction CPL P1.5 in the 8051 microcontroller performs which action?
  1. Toggles the current logic level of the pin P1.5 (if it was high, it becomes low, and vice versa).
  2. Sets the pin P1.5 to high.
  3. Clears the pin P1.5 to low.
  4. Reads the status of the pin P1.5 into the Accumulator.

Correct answer: A

Explanation

CPL means complement. Applied to a bit-addressable pin such as P1.5, it replaces the bit by its logical complement: 1 becomes 0 and 0 becomes 1.

Formula

P1.5 ← NOT(P1.5)

Step-by-step solution

CPL Bit Instruction explanatory diagram

Correct Answer

A — Toggles the current logic level of the pin P1.5 (if it was high, it becomes low, and vice versa).

Explanation

CPL means complement. Applied to a bit-addressable pin such as P1.5, it replaces the bit by its logical complement: 1 becomes 0 and 0 becomes 1.

Key Concept

CPL Bit Instruction

Formula

P1.5 ← NOT(P1.5)

Exam Point

CPL = Complement = Toggle.

Exam tip

CPL = Complement = Toggle.

Quick method

CPL = Complement = Toggle.