AB retentive counter?

RobertB

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Join Date
Oct 2017
Location
WI
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Hi, all.
I have a need for a retentive counter. PLC is an Micrologix 1200. I see that Siemens can do a retentive counter. I can't find how to do one with AB. Any clues. Much thanks as always!!
 
Hi, I was curious also. I looked in RS 500 instruction help and I found some counters named "up counter/hold" etc. In alphabetical order they're way down at the bottom of the list. ("U") Maybe that will help you.
 
Hi, all.
I have a need for a retentive counter. PLC is an Micrologix 1200. I see that Siemens can do a retentive counter. I can't find how to do one with AB. Any clues. Much thanks as always!!

The CTU instruction counts up, and it keeps counting after you reach the preset .. and the done but (.DN) comes on.

When you reset it (RES) .. it clears the done bit and changes the accumulated value (.ACC) to 0.

It retains the ACC value over a power cycle .. which is my definition of retentive.

What do you want it to do that it does not do?
 
All data in a Micrologix is retentive. If you want the PLC data to change on power up or at any other time, you must explicitly program it to do so. That is how all PLCs should behave IMHO.
 
Sometimes, it is the simplest things. The 1200 mentioned earlier is running a production line right now, so I can't mess with it. But I have a ML1400 here ready to go. I'll give it some counts and then power cycle it.

Thanks!!
 
Mr. OkiePC.

Threw in a counter and gave it 30 hits.
Power cycled it. After 2 minutes, powered back up and counter STILL had a 30 count. It does have a battery back up.
But it is safe to assume that if I pull the battery and lose the program.... I would lose the counter value too.
Thanks for the help.
 
Mr. OkiePC.

Threw in a counter and gave it 30 hits.
Power cycled it. After 2 minutes, powered back up and counter STILL had a 30 count. It does have a battery back up.
But it is safe to assume that if I pull the battery and lose the program.... I would lose the counter value too.
Thanks for the help.

Yes, that is safe to assume.

I do believe that you can power down with no battery for a short period of time and retain memory, but if you lose any of it, you will lose it all. The SLC has a capacitor that keeps memory intact for up to 30 minutes (according to the book). I have had a SLC keep memory for over 24 hours with no battery! I have a Micrologix 1100 I can test this on, but in any case your assumption is correct and most of this paragraph is either the exception to the rule or not true for a Micrologix.
 

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