mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 508

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

Functional Description
Data flash memory is useful for applications that need to quickly store large amounts of
data or store data that is static. The EEPROM partition in FlexRAM is useful for storing
smaller amounts of data that will be changed often.
23.4.2.3 EEPROM Implementation Overview
Out of reset, the partition settings (EEESIZE, DEPART) are read from the data flash IFR
and the EEPROM file system is initialized accordingly. The EEPROM file system locates
all valid EEPROM data records in EEPROM backup and copies the newest data to
FlexRAM. The FCNFG[EEERDY] bit is set after data from all valid EEPROM data
records is copied to the FlexRAM. After the EEERDY bit is set, the FlexRAM is
available for read or write access.
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 FCNFG[EEERDY] bit is set.
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.
508
Figure 23-30. FlexRAM to FlexNVM Memory Mapping
EEPROM partition
Unavailable
FlexRAM
MCF51JF128 Reference Manual, Rev. 2, 03/2011
FlexRAM base
address
Preliminary
FlexNVM base
address
EEPROM backup
Data flash
FlexNVM
Freescale Semiconductor, Inc.