46

3638F–DFLASH–4/08

AT45DB021D

Figure 25-2. Algorithm for Randomly Modifying Data

Notes:

1. To preserve data integrity, each page of a DataFlash sector must be updated/rewritten at least once within every 10,000

cumulative page erase and program operations.

2. A Page Address Pointer must be maintained to indicate which page is to be rewritten. The Auto Page Rewrite command

must use the address specified by the Page Address Pointer.

3. Other algorithms can be used to rewrite portions of the Flash array. Low-power applications may choose to wait until 10,000

cumulative page erase and program operations have accumulated before rewriting all pages of the sector. See application

note AN-4 (“Using Atmel’s Serial DataFlash”) for more details.

START

MAIN MEMORY PAGE

TO BUFFER TRANSFER

(53H)

INCREMENT PAGE

ADDRESS POINTER

(2)

AUTO PAGE REWRITE

(2)

(58H)

END

provide address of

page to modify

If planning to modify multiple

bytes currently stored within

a page of the Flash array

MAIN MEMORY PAGE PROGRAM

THROUGH BUFFER

(82H)

BUFFER WRITE

(84H)

BUFFER TO MAIN

MEMORY PAGE PROGRAM

(83H)