>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?

Texas Instruments have some nice SRAMs with in-built backup battery.

http://focus.ti.com/docs/browse/productnavigation.jhtml?familyId=473&tfsection=products&templateId=2

Also SRAMs with RTC and in-built crystal & battery.

http://www-s.ti.com/cgi-bin/sc/family3.cgi?family=REAL-TIME+CLOCKS

The really nice thing is you can order free samples. :-)

Regards
Jean-Michel.

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