power failure interrupt on NIOS 2

We use a Simtek part that has a shadow RAM/EEPROM in it. When power is applied to the part, the contents of the EEPROM are transfered to the RAM. During normal operation you use it just like RAM. When power is removed, the part senses this and transfers the RAM data to the EEPROM. All you need is an external CAP (besides VDD) that keeps the power on the chip active long enough for the transfer. It seems kind of scary, but we have found this device very reliable. If you don't trust the automatic transfers, the part supports the transfers under software control.

With this part, there is no need for a low power interrupt handler for our NVM. However, you may have other cleanup activites that need to be done besides the NVM. Your question is valid and I'm also interested in the best way to handle power down conditions.