Best practices upgrading PLC program

[otrotabi]

This is the scenario. I have a working PLC and I want to add some new features.  These new features require some new EEPROM variables and the variables which are present on the PLC may have been modified by the user. There are also some new Status variables which have been created.

Since I have modified the original program, I think I can not connect to the PLC and upload the EEPROM variables which are already on the PLC with the commissioning tab, because my table is actually  different from the original table (because I have added some new variables).

What happens if I only download the PLC and HMI programs without using the download all feature ? What values do these new EEPROM variables take by default ? And what if during program upgrade some previously used EEPROM variables get assigned new addresses ? 

I think you get the point, and maybe you can give me some tips on how to tackle this problem.

Thanks in advance.

[FedericoM]

Hi,

parameters of M172 are stored in the EEprom (Flash area in case of Secure Interface and M173O) based on the row order of the parameter table.

So if you add new parameters at the bottom of the table and you download just the plc code the older parameters will not change their value and the new ones will have value FFFFh (-1).

If -1 is out of the nominal range of the parameter, you can add few lines of code in the init task which autoinitialize the parameter.

If you are not in this case you should first export the PARAM.DAT to usb (or load settings and store them in a recipe), upload PLCIEC.COD and PARAM.BIN with default settings (or a download all), load the PARAM.DAT previously exported or write the recipe.

[otrotabi]

Hi Federico, thanks for your answer. I understand the first solution. However I would like to understand a little bit clerarer: when you say row number don´t you mean register number ? I thought actually the register is what actually identifies the data inside memory.

If I look at my EEPROM table data, I can see there are some data registers missing, variables I created and then deleted. I never re-arrange them so that they are in order (which maybe not good practice) so when I add a new variable, it is likely this unused registers will be used, what happens then ?

Regarding the second part, I wonder if you could explain it further or maybe point me to the right information.

Regards