ST Microelectronics makes the M41T11, its a I2C clock calendar plus
56 bytes of RAM.  It has all the backup battery switching built in,
but not the battery itself.  It uses a watch crystal and has a cool
digital calibration trick to do accuracy trim.

They have a web site, but I don't have the URL handy.  AltaVista can
find 'em.

------------
Barry King, KA1NLH
Engineering Manager
NRG Systems "Measuring the Wind's Energy"
Hinesburg, Vermont, USA
barry@nrgsystems.com
"The witty saying has been deleted due to limited EPROM space"