How to backup/save the internal ACE PLC tags (coder positions, counters,..) in the HMI ?


The ACE PLC has an internal data-log that allows it to save its variable tags in case of a power failure.

However, the backup must be done carefully because it is written in an EEPROM. Like any EEPROM, the limit of the number of writing is about 100000 cycles.

The subject, here, is to save the internal variables of the ACE in the HMI which integrates a backup battery.

To do this, simply use the HMI register from LW50000 to LW51993 : These registers is backuped in case of power failure. See Useful Reserved Registers of HMI

In vBuilder

Add in the ACE PLC Modbus register all the tags of the ACE PLC that you want to save in case of power failure

Don’t forget to allow writing in the tags.

In HMI-Tool

Add the address of the word or bit to be transmitted in the “Data forward” with:

  • “Data type”: 16 or 32 bits (< ! > the 32 bits will use 2 registers)
  • “Source address”: Use a free register from LW50000
  • “Mapped address”: The ACE PLC Modbus register, of the tag to be backuped
  • “Description” : Optional. The name you want.

MyValueSaved at the 4×0 register addres in the ACE PLC


Now, after a restart of both equipment (ACE and HMI), the HMI will write the tags to the ACE PLC at start-up.

If the ACE PLC tag changes its value, the HMI will take this change into account.


About the HMI tags to be also backuped/saved (Numerical input, process parameters,…)

Example for “Numercial input”

Add a numerical input field: Click on this tool 

To save this digital input in case of a power failure, we will write its value to the saved area of the HMI register: LW50000 to LW51999

Then, we copy this value into the ACE register to find it in the PLC.