>My microcontroller circuit has a 62256 (32Kx8) RAM chip, which is used for >storing some important data I want to retain even when the power is off. >What is the normal way to retain data on RAM? Is using a battery the best >solution? If so, how do I turn on the battery "only" when the power is off? John, I've used Analog Devices' ADM695 more than once for jobs like this. It handles backup battery switchover as well as chip select gating and a few other functions that are very useful in most small embedded systems. It has performed flawlessly... Mike Hardwick, for Decade Engineering -- Manufacturer of the famous BOB-II Serial Video Text Display Module! -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body