How to use TMP87P809N with any EEPROM so that I can save timer counting of CMOS RAM in EEPROM for backup, I want to save that counting if electricity get failed and restart.

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    \$\begingroup\$ Please provide a link to a datasheet if you refer to uncommon ICs. \$\endgroup\$ – Federico Russo May 5 '12 at 11:21
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    \$\begingroup\$ The fact that you refer to it as the "CMOS TMP87P809N" says something about its age. Probably dates from when a uC still was NMOS. Microcontrollers have been CMOS for eons! \$\endgroup\$ – Federico Russo May 5 '12 at 11:40
  • \$\begingroup\$ @Federico - Datasheets to TMP87xxx are nowhere to be found on the Toshiba website. Almost certainly obsolete. \$\endgroup\$ – stevenvh May 6 '12 at 12:51

The TMP87P809N is an old microcontroller, rather limited in features, having neither SPI nor I2C on board. It's also OTP, while most controllers today have Flash program memory, so that you can reprogram them. Any reason why you would use that particular controller?

I could not find the TMP87P809 on Digikey (availability problems as well?), but the TMP87P808 is probably comparable and costs USD 6.62! That's Bloody Expensive™. You can easily find microcontrollers with many better features at a fraction of that price, and they will often have the EEPROM on-chip. I would seriously advice against the Toshiba.

Anyway, for a controller without serial interfaces like the TMP87P809N I would suggest to use an SPI EEPROM, as SPI is easier to bit-bang than I2C. The 25AA010 can hold 128 bytes of data.

further reading
Recommended Usage of Microchip SPI Serial EEPROM Devices, Microchip AN1040.


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