AN2014 datasheet(58/65 Pages) STMICROELECTRONICS

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Power supply loss and application reset

AN2014

58/65

DocID10701 Rev 10

6.3

Robust software and default operating mode

In sensitive applications such as automotive, safety or medical applications, it is not

acceptable for a system to enter a locked state or an endless loop, because of bad

EEPROM communications. In many cases, simple software rules can help to secure

operation of the application.

•

WRITE: It is recommended to add a time-out counter to the Write data polling loop to

prevent the application from being locked if, for some unknown reason, the application

software cannot exit from an endless Write data polling loop. After each write cycle, the

software should always verify that data has been correctly programmed by reading

back the data.

•

READ: When reading data from the EEPROM, the application software should check

whether the data value is within an acceptable range and, if not, switch to a default

value allowing continuity in the application operation.

•

As recommended, data in the EEPROM can be duplicated and associated with a

checksum and an Error Code Correction mechanism. In particular default parameters

can be stored in a protected part of the memory array (Read-Only array, the write-lock

being defined by software) or in another available non-volatile memory. The MCU

should then be able to access an external memory in order to copy the missing

parameters back to the EEPROM.

•

Moreover, it is safer to have a default operating mode that can run with a reduced set of

default parameters.

Refer also to Section 5.3: Write protection and Section 5.4: Data integrity.

AN2014 датащи(PDF) 58 Page - STMicroelectronics