SLC 500 Tag values through power cycle

realolman · Jul 30, 2015

If I were to download a program that had a tag called "Count" that had an initial value of zero, and I MOVed the value of a counter accumulator (which was 5) into Count, and then I cycled power to the SLC, what would be the value of Count?

I'm thinking 5... am I correct?

thank you

bernie_carlton · Jul 30, 2015

it should be retained assuming you have a functioning battery. You should check with any different PLC you may use. Not all of them do this automatically.

Bit_Bucket_07 · Jul 30, 2015

What Bernie said. Register data is retentive in most PLCs, including the SLC family, although discrete bit data usually isn't. Some PLCs offer specific memory addresses or options to select retentive status for bits through a power cycle. Some don't. Most PLCs reset all output bits on power up, whether they are real IO bits or internal logic bits.

realolman · Jul 30, 2015

so the definite answer is probably.

thank you..

OkiePC · Jul 30, 2015

Definitely, unless...

Unless you have a memory module installed and the related system bit settings and power up circumstances caused the PLC to load from the memory module.

Bit_Bucket_07 · Jul 31, 2015

Yep...

There's always an exception to the rule, but generally speaking, register data will be retained through a power cycle in an SLC.

SLC 500 Tag values through power cycle

realolman

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bernie_carlton

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Bit_Bucket_07

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realolman

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OkiePC

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Bit_Bucket_07

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