I can't give much detail since I haven't used it myself. However the RTC in the M5223X is not designed to be a low power RTC with battery backup. It runs when the processor is up but (as far as I know) not when it is down. I believe it gets its clock from the main oscillator.
The explaination at the freescale seminar was that Ethernet based applications are not target at lower power and this feature is therefore not a goal.
However I do have an application with the device where we need RTC support and so are also contemplating the best way to do it. It will probably use an external Dallas device via I2C with battery backup. On the otherhand, if we can be sure that there is normally Internet access we may use NTP (Network Time Protocol) to get the time from a time server when booting and then run the RTC when powered....
Maybe someone has used the RTC and can give us both some more detail?
Meanwhile I got some information about Kirin RTC.
I confess I´m very disappointed to Freescale about it.Such argument that the device doesn´t need battery support to work due to online connectivity is totally missunderstood....There are a lot of application wich are assited by RTC information, like logs, schedulled procedures, general controls, etc,etc,etc EVEN THEY ARE OFFLINE (and so,not using a 32KHz...) , or (worst) have lost the power and wakeup at the moment the link is offline. I understood the MCF52235 implemented RTC is nothing more then a hardware counter wich could be easily done by a sw routine, like we already do for 9S08GT/BB mcus, and certainly would not "overload" a 32bits machine.Even so Kirin is a very nice option for its segment, but in my opinion a traditional company like Freescale should not introduce a feature by this way, I mean...half feature
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