How to perform a backup SRAM, enter the Backup menu.

Mori Seiki lathe (control of Mitsubishi Meldas)
Model: NL2500 SMC / 700
A lot searched the internet in this topic. Then I tried different combinations of keys & starts the machine but without success.

What is interesting: not having literally no experience with Mori Seiki NL2500 after about 2 months of work, within the framework of machine learning I entered in various settings. And I was able to enter the SRAM backup mode (black screen, as in the service menu, where the choice was a Y or N). Unfortunately, little time has passed and I can not remember where it was, and a little time spent on it.
I did not look like a novice, now I can calibrate the probes, change the language ... has remained a problem with backup
Sorry for my English.

Greets Krynio