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Updated 2025-11-10
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Masked Compare

MEQ - Masked Compare

Compares specific bits of two values using mask to ignore certain bits.

Key Takeaways

  • Compares specific bits of two values using mask to ignore certain bits.
  • Advanced-level topic in Ladder Logic Elements

Detailed Definition

Compares specific bits of two values using mask to ignore certain bits. This term is essential for understanding ladder logic in industrial automation and PLC programming.

Masked Compare is part of the visual vocabulary of ladder logic, the relay-derived language that virtually every PLC vendor still supports. Compares specific bits of two values using mask to ignore certain bits.

Masked Compare is evaluated as part of the PLC's deterministic scan: inputs are sampled, ladder rungs run in sequence, outputs are written, and the process repeats. Masked Compare sits inside that program-execution phase, where its specific logical or temporal behaviour shapes how the rung resolves.

For ladder programmers, Masked Compare is one of the components you reach for instinctively after enough rungs. The visual nature of ladder makes it readable to electricians and operators in a way that text-based languages aren't, which matters in environments where maintenance happens at 2 AM by whoever is on call.

Common Questions

What is Masked Compare?

Compares specific bits of two values using mask to ignore certain bits.

What prerequisites are needed to understand Masked Compare?

As an advanced-level concept, Masked Compare requires a solid foundation in PLC fundamentals and intermediate programming concepts. It's recommended to have hands-on experience with Ladder Logic Elements before diving deep into this topic.

What are related concepts I should learn?

To fully understand Masked Compare, you should also familiarize yourself with TON (Timer On-Delay), TOF (Timer Off-Delay), and CTU (Count Up). These concepts work together in industrial automation systems.

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Quick Info

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About Ladder Logic Elements

Contacts, coils, timers, counters, and ladder diagram components

Total Terms:70
Difficulty:Beginner to Intermediate

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