Choosing real time clock

[santosh]

We are using MC9s08GT and want to use an rtc.
But witch one is the best clock? Make it sense to use the I2C Interface? The SPI is allready used.

Thanks for help.

[Wings]

If really low power is a requirement, check out the DS2417. 1-wire interface & programmable pulse output. Draws around 180 nanoamps @ 3v. Doesn't have clock registers, just a 32-bit count of seconds so you'll have to do your date & time thing in software.

[Encoder]

I have been using a PCF8583 on my old HC705B controller for years, with a synthetic IIC from 2 I/O lines, and one of the 2 was multiplexed with another peripheral.

Perhaps today I would use the DS1337 which seems to be newer and cheaper. It too uses IIC.

Encoder

[mke_et]

I'm using the DS1307Z on my new design.  It's I2C and seems pretty simple to implement.

Mike