Hello Nice te be part of this group
I hope i meet new friends and shere experience.
I found the troubel at the RAM of module controller.RAM [U3] always reset and does not save when device in turn off and turn on again.But for the time setting remains stored on the on the other RAM [U1].Both were connected to a battery backup that have normal value 3 volts.
1. I would like to ask in the condition of the good battery what causes that make U3 does not save other setting parameter?
2. If I want to replace U3 because it is broken is there any specific requirements that I need to do to connect with microncontroler?

This is datasheet of the RAM
U3
http://www.alldatasheet.com/datasheet-pdf/pdf/23508/STMICROELECTRONICS/PSD413A1-C-70U.html

 

Welcome to AAC!

What is the battery voltage?

The datasheet for PS413 states Vstdby can't be less than 2.7V. It looks like Vbat for U1 can be as low as 2.5V.

 

lithium battery ,i measure at the Vstdby terminal 3 volt. I think U1 is good becouse the time setting still saving.

 

lithium battery ,i measure at the Vstdby terminal 3 volt.

Is this measurement with the device off?

 

yups...to make sure that the RAM stil gets voltage when the device in off condition