Micrologix 1000 question

How does the backup situation work with the Micrologix 1000? If setpoints are changed in the PLC will it hold those if you power it down? or will it default back to whatever is set in the program that was downloaded to the PLC? Assuming that no type of logic is written to write setpoints back to default using the first scan bit.

They will be held in the ram memory

diat150 said:

How does the backup situation work with the Micrologix 1000? If setpoints are changed in the PLC will it hold those if you power it down? or will it default back to whatever is set in the program that was downloaded to the PLC? Assuming that no type of logic is written to write setpoints back to default using the first scan bit.

Click to expand...

The Micrologix 1000 has a backup battery, which should hold all of your setpoints, timer presets, counter presets, etc at their last value until something changes them

If the battery is low or missing, the values as well as the program will be lost when power is lost.

Then you load the program from your programming terminal - usually a PC. And the program, along with all of the data, is weeks or months or years out of date, so your data is restored to the value it was the last time you saved the program.

You can go online and save your program to your computer whenever you want, but it is a manual process

To my surprise, the MicroLogix 1000 doesn't have a backup battery !

My understanding is that those controllers write to EEPROM every time they power down. Because they have such a tiny memory, their EEPROMs can tolerate hundreds of thousands of power cycles.

You could theoretically wear out a MicroLogix 1000 EEPROM and lose the retentive values (similar to when a voltage spike wipes them out; you would get a S:5/8 Retentive Data Lost fault) by power cycling it a few hundred thousand times.

The MicroLogix 1200 is like that as well, but uses a Flash memory device instead of an EEPROM. All the other MicroLogix have a battery.

Just to confirm...

Battery: No

565038 - Does the MicroLogix 1000 have a replacement battery
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...&...

59845 - MicroLogix Processors that require a battery to retain user project and data
Access Level: Everyone

Memory: 1K EEPROM

27102 - MicroLogix 1000, 1100, 1200, 1400 and 1500 Memory Types and Sizes
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External Memory option of a sort: HHP

16122 - MicroLogix 1000 hand-held Programmer ( HHP ) using a Memory Module
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...&...

25201 - How to use the 1761-HPP-B30 with the MicroLogix memory and the HHP memory module
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Load from Memory Module: No (only HHM in HHP)

67588 - Is there a memory module for the MicroLogix 1000?
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Data File Protection: No

9550 - File Protection Options for SLC and MicroLogix Controllers
Access Level: TechConnect

To answer the opening question...

diat150 said:

How does the backup situation work with the Micrologix 1000? If setpoints are changed in the PLC will it hold those if you power it down?...

Click to expand...

Yes - When powering OFF the current Data File values will be saved to EEPROM and then restored at power up.

diat150 said:

...or will it default back to whatever is set in the program that was downloaded to the PLC?...

Click to expand...

No - When a program is downloaded to the controller the offline Data File values are also downloaded, but they are not stored in any special memory or way so that the values could be referenced for a future "default" operation to restore the Data File values back to an "as downloaded" state.

After downloading the program - as soon as the Data File values are manipulated, manually or by the running program, the original values are now overwritten. At any point in time that the controller is power cycled, the values will now be saved to the EEPROM at whatever value they happen to hold at the time. An address value may happen to be the same as when it was downloaded, or not. If the value happens to be the same then it is just coincidence or perhaps it had never changed since the last download was performed - all application dependent, of course.

diat150 said:

...Assuming that no type of logic is written to write setpoints back to default using the first scan bit.

Click to expand...

You would have to use a method such as this if you do want to automatically default the controller Data File values back to a known Data Set at each power up or "Go to Run". Usually this involves designating addresses within the controller to store the default values to be copied to the working address registers. The default values must never be destructively operated upon - i.e. written to, unless changing a default setting manually.

Other than using a method to achieve similar to this, you would have to perform another download of the program that contains the Data Set you wish to load.

Regards,
George

Thanks for the in depth response George. I am now trying to figure out why the setpoints are being written back.

Hmi / scada?

This thing does have an hmi, I am in the process of installing ccw right now, but I have never seen a hmi setup to write setpoints on startup. not saying its never been done but would be unusual.


My suspicion is that the copy of logic that was provided to me does not match what is in the processor. I have not been to the site to do an upload.

Ahh, gotcha. You're not in front of this controller.

A HMI is less likely to write defaults but many SCADA systems do (I don't mean by default; I mean by design).

I'd prefer have a fresh uploaded copy of the program too, if I was you.

G.

Geospark said:

Just to confirm...

Battery: No

Click to expand...

Ken Roach said:

To my surprise, the MicroLogix 1000 doesn't have a backup battery !

Click to expand...

Thanks for keeping me honest guys.

I am reminded every month or two that I need to rely LESS on my memory and more on LOOKING THINGS UP.