CompactLogix Storing Values

Where should values such as set points or counter values be stored so they don't get overwritten by a future PLC code incremental update.

I am looking for suggestions or best practices.

Do most people load and read from a config file? What is maybe the simplest implementation?

What do you mean by "an incremental update" for a PLC? When PLC code is "updated" it is generally done by pulling the code off of the current machine, making changes to that particular file and then putting it back on the machine.

You can store values that might be tweaked from an HMI or such in something called "retentive memory" so that they are not lost on power cycle, or store them in the HMI and have the PLC attempt reading those values from the HMI on a power cycle as well.

That being said, I'm curious to hear what others have to say on the subject as well.

a)If you work online there's no need to worry about overwritten setpoints.

b) If you need to work offline, you can upload the application from the PLC, add/modify/delete the logic, and download it into the PLC.

c) Also it's possible to write/read values from the memory card (if the controller has a CF/SD card). In this case you'll need to write the logic for saving/retrieving data, including the HMI display to invoke those functions.

Look for the "Data Preserved Download Tool"