Power loss and data corruption

AN2440

10/13

Doc ID 023074 Rev 4

4.2

Read-only parameters

When using an EEPROM with an embedded ECCx4, it is recommended to pay particular

attention to the data mapping of read-only bytes and read/write bytes.

Read-only data handles key values for the end application and this data must never be

changed even if some uncontrolled events, such as a power-down during a write cycle,

occur.

As we know that a power-down during a write cycle can modify the four data bytes inside the

addressed word(s), a word should not store read-only byte(s) and read/write byte(s). For a

robust application design, it is a necessary condition to define two separate families of data:

●

Read-only data which is only read during the application life.

●

Read/write data in which the bytes can be updated during the application life.

Read-only data must be stored in words different from the words in which the read/write

data is stored. (read-only data and read/write data must never be stored in a same word.)

Thus, an unexpected voltage supply drop during a write cycle will never corrupt read-only

e.

This is not tested in production but only characterized during the product qualification.