Micorcontroller RAM with battery backup?


does anyone know of any micro controller which can give me a battery backup on the inbulit RAM?

i need to store some values into the RAM through some MMI and want them to be avaliable everytime on power up without re-entering the values.

i could use external NV RAM with battery backup but then i'd have to use port 0,2 for addressing and i would like to keep it for I/O.

any ideas? appreciate it.


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I do know that 68HC11's have a RAM standby power pin.

Why don't you write the values to EEPROM, or Flash ROM instead. You could even use a small serial EEPROM, and bit bang the data to it.

Hope this helps,

Mike Anton

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Michael Anton

Get a serially interfaced ferroelectric RAM, see .


Tauno Voipio tauno voipio @ iki fi

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Tauno Voipio


there are small microcontrollers from Microchip, Motorola, Philips that have EEPROM integrated for less than $1 (if you need 1k units). They would also have very low power standby values, you could keep the whole RAM contents with approx. 1uA. If you check Microchip, look for nanopower (PIC16xx), checking Motorola look for HC08, checking Philips look for LPC900-family

Hope this helps, Schwob

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Hi, many micros have a sleep mode which allows you do retain memory without the chip running. You can't use flash or eeprom as general ram because of the slow write speed.

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Just about all of them these days. Usually the minimum voltage for RAM data retention in sleep mode is lower than the minimum voltage for operation.

Best regards, Spehro Pefhany

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Spehro Pefhany

The Dallas 8xC530 8051-type µcontrollers have a battery backup circuitry for the internal SRAM.


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Jan Weber

does this also hold good for when the entire circuit is powered down?

no Vcc, nothing.


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