After perusing all/most available documents for the 5223x series, I can't seem to find any information on the holdup or external battery capabilities for the onboard real time clock. Any help in pointing me toward more information regarding this would be greatly appreciated.
There is no battery backup for the Real Time Clock on the 5223x series. We spoke with a Freescale FAE this week and he said that Freescale discussed it but it would have required major silicon change.