Hi
Earlier S12 and S12X microcontrollers contained standard EEPROM memory. The main characteristic (from the user’s point of view) is that the sector size is 4 bytes (smallest partition of memory that can be erased).
Microcontrollers from S12XE and S12XF family are a little bit different. The technology has been changed – the memory size is higher but also the sector has been increased to 256 bytes. This kind of EEPROM memory is called D-Flash.
There are two ways to access this memory.
The user can work with the D-Flash directly – through the standard flash commands like “Program D-Flash Command”, “Erase D-Flash Sector Command”…
The next possibility is usage of Emulated EEPROM. What does it mean – the user just reads/writes data from/to Buffer RAM. The internal mechanism will ensure the data integrity between Buffer RAM and D-Flash. It automatically loads data from D-Flash to Buffer RAM after reset and automatically stores the data to D-Flash when writing to Buffer RAM. So, it’s very comfortable for user because he can use the EEPROM memory which behaves like RAM memory.
This is only short description, I recommend the application note AN3490 where is the complete explanation.
http://www.freescale.com/files/microcontrollers/doc/app_note/AN3490.pdf
Have a great day,
Jennie Zhang
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