Peripheral operating requirements and behaviors
Table 21. NVM reliability specifications (continued)
Typ.1
Symbol Description
Min.
Max.
—
Unit
years
cycles
Notes
tnvmretd1k Data retention after up to 1 K cycles
nnvmcycd Cycling endurance
20
10 K
100
50 K
—
2
FlexRAM as EEPROM
tnvmretee100 Data retention up to 100% of write endurance
tnvmretee10 Data retention up to 10% of write endurance
Write endurance
5
50
—
—
years
years
20
100
3
nnvmwree16
nnvmwree128
nnvmwree512
nnvmwree4k
nnvmwree8k
• EEPROM backup to FlexRAM ratio = 16
• EEPROM backup to FlexRAM ratio = 128
• EEPROM backup to FlexRAM ratio = 512
• EEPROM backup to FlexRAM ratio = 4096
• EEPROM backup to FlexRAM ratio = 8192
35 K
315 K
1.27 M
10 M
175 K
1.6 M
6.4 M
50 M
—
—
—
—
—
writes
writes
writes
writes
writes
20 M
100 M
1. Typical data retention values are based on measured response accelerated at high temperature and derated to a constant
25°C use profile. Engineering Bulletin EB618 does not apply to this technology. Typical endurance defined in Engineering
Bulletin EB619.
2. Cycling endurance represents number of program/erase cycles at -40°C ≤ Tj ≤ 125°C.
3. Write endurance represents the number of writes to each FlexRAM location at -40°C ≤Tj ≤ 125°C influenced by the cycling
endurance of the FlexNVM (same value as data flash) and the allocated EEPROM backup. Minimum and typical values
assume all byte-writes to FlexRAM.
6.4.1.5 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 flash
memory module 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.
EEPROM – 2 × EEESIZE
Writes_FlexRAM =
× Write_efficiency × nnvmcycd
where
• Writes_FlexRAM — minimum number of writes to each FlexRAM location
K20 Sub-Family Data Sheet, Rev. 4 5/2012.
Freescale Semiconductor, Inc.
33
FREESCALE [ Freescale ]
