FlexNVM as E-Flash:
As shown in the figure above, Data retention is only 5 years, and data retention can be restarted by refreshing the data, so my question is,if one data in FLEXNVM is refreshed, the data retention of other unchanged data will be recalculated for 5 years?
The second question, the more times the data is refreshed, the actual physical address(in FlexNVM) of the data that is not refreshed will change?
Is there any other solution to improve data retention for 10 years？
Hello liuruowen@hangsheng.com.cn,
The NVM specification has changed recently.
Please see the table below (S32K1xx datasheet rev.13).
If I understand, you are asking whether the retention of records that are static (written only once) can be extended beyond 5 years without rewriting them in FlexRAM.
As you can see, if the endurance is less than 10%, the retention of the data is guaranteed for 20 years.
If the endurance is >10%, the retention is 5 years only, but it can be extended by the background maintenance (footnote 4, Table 38).
The background maintenance operation on the static records takes place when the EEPROM state machine needs to erase a sector because there is no more space left for new records or updates.
The EEPROM stores 64 bits (data + information about the data) into the EEPROM backup flash (FlexNVM) for each 32b record (FlexRAM).
If the whole FlexNVM (64kB) is used as EEPROM backup, it can store 8192 32b records (or updates) before it needs to do the background maintenance - erase sectors and refresh valid records including the static once.
So, if the endurance is >10% and you need to extend the retention (by another 5 years) of some static records, you need to update other records (as many times as it needs to fill the backup flash) so that the maintenance can take place.
Regards,
Daniel
As above，what does a new question 10% or 100% mean? How to judage this parameter in my project？
Thanks
Hello，Daniel：
Thanks for your relay.
So,I can use software（
See below：
The percentage in the figure above is calculated as follows: 10027/100K = 10% right?
①: If there is no red part in the curve, that is, all static variables and dynamic variables will be saved for 20 years, right?
Thanks.
Hello Liu,
The Estimated Flash Cycles that you highlighted shows the number of erase cycles on the EE backup flash, it is not the endurance.
As I already mentioned, the endurance is given by the ratio between FlexRAM that is used for the EE records and the EE backup flash.
If the whole FlexRAM is used and the whole FlexNVM is partitioned for the EE backup,
the ratio is 16 = 65536B (backup) / 4096B (FlexRAM), and each record can be updated 100k times.
But if only 256 bytes of FlexRAM is used,
the ratio is 256 = 65536B / 256B and then each record can be updated 1.6M times.
(FlexRAM available / FlexRAM used) * 100k = 100% endurance
As you can see below 64 * 4B = 256B can be updated 1.6M times.
Regards,
Daniel
Hello，Daniel：
sorry，I still can't understand.As below：
if the ratio is 16, 100% is 100k. 10% is 10k？If I update less than 10k ，the endurance is less than 10%？ right？
Can you give me example for below：
for example，S32K144,64KB(back up),4KB(FlexRAM),but only 900 bytes is actually used, what percentage is this？
Thanks。
Hello Liu,
Yes, if the backup is 64k and 4k of FlexRAM is used, the ratio = 16, the endurance = 100k and 10% of it is 10k.
If only 900B of FlexRAM is used,
the ratio = 65536 / 900 = 72.8178
72.8178 / 16 = 4.55111
This is 4.55111 * 100k = 455,111k endurance.
Or we can say, since only 900B of 4096B is used, and the endurance of the whole 4096B is 100k.
4096 / 900 = 4.55111
The endurance of 900B is 4.55111 * 100k = 455,111k
If we use the calculator, we can see that 225 (4B) records (225 * 4 = 900) can be updated 455111 times:
But not 455112 times
Hope it helps,
Regards,
Daniel
