When configured for EEPROM use, writes to an unprotected location in FlexRAM
invokes the EEPROM file system to program a new EEPROM data record in the
EEPROM backup memory in a round-robin fashion. As needed, the EEPROM file
system identifies the EEPROM backup sector that is being erased for future use and
partially erases that EEPROM backup sector. After a write to the FlexRAM, the
FlexRAM is not accessible until the FSTAT[CCIF] bit is set. The FCNFG[EEERDY] bit
will also be set. If enabled, the interrupt associated with the FSTAT[CCIF] bit can be
used to determine when the FlexRAM is available for read or write access.
When configured for EEPROM use, attempts to write to the FlexRAM are ignored in
VLP mode .
After a sector in EEPROM backup is full of EEPROM data records, EEPROM data
records from the sector holding the oldest data are gradually copied over to a previously-
erased EEPROM backup sector. When the sector copy completes, the EEPROM backup
sector holding the oldest data is tagged for erase.
16.5.3.4 Write endurance to FlexRAM for EEPROM
When the FlexNVM partition code is not set to full data flash, the EEPROM data set size
can be set to any of several non-zero values.
The bytes not assigned to data flash via the FlexNVM partition code are used by the
FTFE to obtain an effective endurance increase for the EEPROM data. The built-in
EEPROM record management system raises the number of program/erase cycles that can
be attained prior to device wear-out by cycling the EEPROM data through a larger
EEPROM NVM storage space.
While different partitions of the FlexNVM are available, the intention is that a single
choice for the FlexNVM partition code and EEPROM data set size is used throughout the
entire lifetime of a given application. The EEPROM endurance equation and graph
shown below assume that only one configuration is ever used.
Writes_FlexRAM =
× Write_efficiency × n
EEPROM – 2 × EEESIZE
EEESIZE
nvmcycee
where
• Writes_FlexRAM — minimum number of writes to each FlexRAM location
• EEPROM — allocated FlexNVM based on DEPART; entered with the Program
Partition command
• EEESIZE — allocated FlexRAM based on DEPART; entered with the Program
Partition command
• Write_efficiency —
Chapter 16 Flash Memory Module (FTFE)
Kinetis KE1xZ256 Sub-Family Reference Manual, Rev. 3, 07/2018
NXP Semiconductors
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