AN2540 - Application note

Implementing the EEPROM emulation

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Figure 7.

– User-configured emulated EEPROM size.

– Increased Flash memory endurance: Sector erased only once it is full.

– Non-volatile data variables can be updated infrequently

– No need to perform a write operation if the updated value is the same.

– Interrupt servicing during program/erase is possible.

3.4

Program execution

Independently of the implementation scheme, the STR91xFxx internal Flash memory offers

the ability to update a bank while code is executed from the other bank. Therefore, there is

no need to transfer Flash memory operations (Program/Erase) to RAM. However when the

CPU frequency is higher then 25 MHZ it is recommended to copy some routines into RAM

This means that before erasing and programming, a few software routines have to be copied

from the Flash memory into the on-chip RAM. Should be copied at least the routines used

for the erase and program operations, and the routines that run while the erase or program

operation is ongoing.

Add element request

full

current active

sector

Add new element at

the 1st empty element

place in the current

active sector

Erase previous active sector

End

End

Change the active sector

Find Valid sector

Yes

No

FindValidSector()

WriteVerifyVariableFull()

Copy all current elements by

reading the active sector

from the bottom, taking

into account the new

updated element.

EepromSectorTransfer()

ReadVariable()

Function call

ai14091

Check

value

same

different

End