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Old February 8th, 2018, 04:48 AM   #4
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It is just RTO - not RTON.

It works exactly the same as a TON, except that it doesn't automatically reset when disabled. To reset it, use the RES instruction, with the timer tag name as the parameter.

It sounds like you don't ever want it to "time-out", because if it did it would just "freeze" with the .DN bit set, and will not accumulate any more time. Set the .PRE to 2,147,483,647 (maximum positive value of a DINT), which equates to 2,147,483 seconds, or just under 25 days of accumulated time.

The good thing about using RTO is that it will hold the accumulator value, not just when it is disabled, but also through power-cycles, and mode changes (RUN-PROG-RUN) of the controller, that is why it is called a "Retentive" timer.
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Last edited by daba; February 8th, 2018 at 04:48 AM. Reason: speeling
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