Question: What are the possible options to design a battery backed up memory interface on a board?
Response: There are a couple of different options. One is to have a diode which would be forward-biased by a battery when the main power supply to the SRAM is turned off. The main power supply should have a decoupling capacitor to supply power to the SRAM for a few milli-seconds before the battery backs up so that the SRAM does not lose any of the data stored in it. The second option would be to have a large capacitor(super cap) which supplies charge to the SRAM when the main power supply is turned off. This might provide charge only for a few minutes.