Difference between FlexNVM as "EEPROM" vs FlexRAM as EEPROM vs D-Flash

[gearhead1107]

I need to run the DEPART command so I can use the CSEc module on my S32K144, however I'm not sure of the best way to partition my device. I see that it's ideal you only do it once.. so no pressure :smileyhappy:

Essentially, I'd like to create a flag in non-volatile memory (whether it be flash or emulated EEPROM) for a simple "flag" to denote an update process has begun. It's not clear to me whether the best place for this is 

• FlexNVM
• FlexNVM emulating EEPROM
• FlexRAM emulating EEPROM

Is the benefit of emulated EEPROM that one can write 1, 2, or 4 bytes at a time? Does this go for both FlexNVM and FlexRAM when they're used as EEPROM?

Is there any actual difference in endurance for any of these modes? Since this flag will be used for every update, I'd like to ensure it's not going to wear out after a bunch of updates.

Are there security access restrictions for any of these areas when using the CSEc module? Ideally, I would like to be able to easily read/ write these areas without an extensive process.

Thank you!

[gearhead1107 · Accepted solution]

And lo, the book of reference, section 33, verse 5, subsection 2, sub-subsection 2, (Reference Manual, Page 755/ section 33.5.2.2) had the answer:

The emulated EEPROM feature is not something you enable for RAM *or* Flex NVM - it has to be enabled for both.

The intended usage is that you access the "EEPROM" via FlexRAM (when properly configured), and the file system handler will store that information in FlexNVM (when properly configured), with 2KB erase sectors. The benefit of this is that the file system handler will automatically move the sectors around in the FlexNVM space, so the durability of the Flash is greatly increased. As such, your partitioning is key here - since the more space you give the file system handler to move your EEPROM blocks around, the longer the FLASH will last.