Which PLC instruction sets an output bit to one when its input becomes true and retains its state after the input loses continuity or power?

Study for the Programmable Logic Controller (PLC) Test. Prepare with flashcards and multiple choice questions, each question provides hints and explanations. Get ready for your exam!

Multiple Choice

Which PLC instruction sets an output bit to one when its input becomes true and retains its state after the input loses continuity or power?

Explanation:
The behavior described is a latch-style output in ladder logic. An Output Latch sets the associated output bit to 1 as soon as its input becomes true, and then holds that on state even after the input goes false. That memory of the on state remains until you explicitly clear it with an unlatch (or reset) instruction, and in many PLCs the latched state can persist across cycles or even power-down if the memory is retentive. The other options don’t fit: a standard input contact simply reflects the current input state without memory; a no-operation does nothing; an unlatch would turn the output off rather than set and retain it. Therefore, this behavior matches an Output Latch.

The behavior described is a latch-style output in ladder logic. An Output Latch sets the associated output bit to 1 as soon as its input becomes true, and then holds that on state even after the input goes false. That memory of the on state remains until you explicitly clear it with an unlatch (or reset) instruction, and in many PLCs the latched state can persist across cycles or even power-down if the memory is retentive. The other options don’t fit: a standard input contact simply reflects the current input state without memory; a no-operation does nothing; an unlatch would turn the output off rather than set and retain it. Therefore, this behavior matches an Output Latch.

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