AT45D021

16

Figure 2. Algorithm for Randomly Modifying Data

Notes:

1.

To preserve data integrity, each page of the DataFlash memory array must be updated/rewritten at least once within every

10,000 cumulative page erase/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/program operations have accumulated before rewriting all pages of the Flash array. See application

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

START

MAIN MEMORY PAGE

to BUFFER TRANSFER

(53H, 55H)

INCREMENT PAGE

ADDRESS POINTER

(2)

Auto Page Rewrite

(2)

(58H, 59H)

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

(82H, 85H)

BUFFER WRITE

(84H, 87H)

BUFFER to MAIN

MEMORY PAGE PROGRAM

(83H, 86H)