J. P. Gilliver (John) said:
Well, it's 2^14, i. e. easily dividable down to 1.
And it is divided down by a ripple divider, to save power.
It's a Motorola part and the part number is a lot
longer than that.
Sure, you could start with a ripple divider from the
4000 era, but then you'd have no way to count hours
minutes seconds and so on. Or set an "alarm" register.
http://en.wikipedia.org/wiki/CMOS_RAM
"such as the Motorola MC146818 or similar"
This site doesn't allow direct linking, so you have to
click a few things to get the actual PDF. The PDF is actually
a scan of a printed databook, as the part predates the
existence of PDF. And in this form, this chip is a
power pig - if you ran it off a CR2032, it would not
last three years.
http://pdf.datasheetcatalog.com/datasheet/motorola/MC146818AS.pdf
Paul