Yes, it is indeed memory w/ some extra functions. But it is more than
that.
Note that the RTC chip (probably) has a battery backup power input
pin. Now when the main power is turned off, the rest of your system
will be effectively dead and any volatile memory in your system that
relies on that main power will develop amnesia.
But if you had something you want to keep in memory even after the
power is off, save it to the RTC chip's memory. The battery backup
will make sure the RTC chip does not develop amnesia.
Now, you will probably be asking... "Why not just use a Flash Memory
for this?". If you look at the datasheet for Flash Memory chips, they
will usually state that it has a life of 100,000 erase cycles AND you
have to erase a whole block at a time. If you want to write to
memory, say every second, then you will very quickly use up the life
of your Flash Memory.
The memory in the RTC chip solves several problems. It is effectivly
a nonvolatile SRAM when the battery backup is availible. It can be
written to for almost an infinite number of times. You do not have to
erase a whole block (typically about 16Kbytes or more) at a time.
I hope this helps. By the way, you may be interested in reading about
FRAM chips. Try
www.ramtron.com
Best Regards,
Quark
