S7 400H startup

[flinana]

Hi,

shouldnt the PLC load its program at startup from the flash memory card if RAM is empty?
i.e After power loss without backuo batteries shouldnt it read from memory card since RAM is empty due to power loss.

tanks

 

[rybrk]

due to power failure ,without backup power dont verify or transfer the program backup.otherwise program will erase.

rybrk

 

[flinana]

sorry i dont understand what u mean about verify or transfer

thanks

 

[dieselvette]

Last time I used an S7-xxx and needed to save data during power loss, I made a recipe which was stored on the memory card. In my case, every hour the recipe (with updated values) would be written to the memory card. I imposed a one-shot at the beginning of the program so that if it were to start from scratch (as in the event of extended power loss) then it would first load the values for the recipe from the memory card before continuing the program.

The problem with this is that you can only re-write the memory card so many times (1,000,000?) before it is "worn-out". In my case a 1-hour update was sufficient, so the memory card should last for about 114 years. If you need to update your memory more frequently, periodic memory card replacement may be a factor in your equipment design.

If I understand your question correctly, then I believe this is the only way to solve the problem.

Nic Van Engen
Electrical Technician