The Micro800 Timer On Off Instruction

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Rockwell's Micro800 line of programmable controllers include support for a few instructions you won't find in RSLogix.

In today's article we'll discuss one of those instructions, the Time-delay On Off (aka TONOFF) instruction.

Those of us who've been programming Allen-Bradley PLCs for some time now have found many uses for the TON and TOF Ladder instructions.

And I'd also wager many of us have found more than one way to implement our own On / Off code as well.

That said, if you get a chance to program Rockwell's small Micro800 line of programmable controllers, one instruction you should check out is the TONOFF, or Time-delay On Off.

This instruction is supported in all three languages, and CCW's help file describes how it works in these simple terms:

“Delays turning on an output on a true rung, then delays turning off the output on the false rung.”

If you think about it, this one instruction replaces what in most cases would be at least three different instructions when using Ladder Logic in RSLogix.

Side discussion: How would you code a Timer On Off in ladder in RSLogix?

That not only makes the code quicker to write, but also easier to read and understand.

Would you like to see the TONOFF in action?

If you do, check out my video below for a demonstration of how it works.

And to learn everything you need to know to setup and start programming the Micro800 line of programmable controllers, check out my Micro800 course at

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Finally, if you have any questions on today's article please feel free to post them at which I visit each weekday to reply to reader's questions.


Shawn Tierney
Automation Blogger and Trainer

Need personalized help? For as little as $25 per month you can get direct access to ask me Rockwell PLC, HMI, and SCADA questions! Learn the details at

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