I'd like to suggest to go through Safety Manual. You can use as voltage thhreshold not only LVR but also LVI and do not start any E/W operation while the voltage is too low. You can also use higher BULK cap at VSUP.
Safety manual fo S12ZVZL can be get on https://community.nxp.com/t5/SafeAssure-Community/bd-p/safeassure if you have signed NDA.
(For NDA you can ask at our suppport pages support.nxp.com )
The flash module has its own machine which is responsible for correct E/W operation through entire operating voltage range.
If your operating voltage is in the required range then you can do operations on the flash.
The flash quality is defined by data retention and reliability. If you exceed number of E-W cycles then quality of the flash is not guaranteed and it can happen to newly written data:
- the period of data retention is not guaranteed
- the data could be incorrectly written ... CRC error
- incorrect erase (erase means write FFFF into a sector and the memory cell is not able to keep the voltage related to "erase" logic level)
There is a mechanizm of reporting single and double bit fault error. (interrupt) The reason is that the phrase which is read has not correct CRC which is always calculated and stred during write and always compared during read.
You have to ensure correct operating range of supply voltage for correct E/W operations. Otherwise, quality parameter for flash performance are not guaranteed.
Best regards,
Ladislav