AT25DF321A Datasheet, PDF (2/58 Pages) ATMEL Corporation – 32-Megabit 2.7-volt Minimum SPI Serial Flash Memory

The physical sectoring and the erase block sizes of the AT25DF321A have been optimized to
meet the needs of today's code and data storage applications. By optimizing the size of the
physical sectors and erase blocks, the memory space can be used much more efficiently.
Because certain code modules and data storage segments must reside by themselves in their
own protected sectors, the wasted and unused memory space that occurs with large sectored
and large block erase Flash memory devices can be greatly reduced. This increased memory
space efficiency allows additional code routines and data storage segments to be added while
still maintaining the same overall device density.
The AT25DF321A also offers a sophisticated method for protecting individual sectors against
erroneous or malicious program and erase operations. By providing the ability to individually pro-
tect and unprotect sectors, a system can unprotect a specific sector to modify its contents while
keeping the remaining sectors of the memory array securely protected. This is useful in applica-
tions where program code is patched or updated on a subroutine or module basis, or in
applications where data storage segments need to be modified without running the risk of errant
modifications to the program code segments. In addition to individual sector protection capabili-
ties, the AT25DF321A incorporates Global Protect and Global Unprotect features that allow the
entire memory array to be either protected or unprotected all at once. This reduces overhead
during the manufacturing process since sectors do not have to be unprotected one-by-one prior
to initial programming.
To take code and data protection to the next level, the AT25DF321A incorporates a sector lock-
down mechanism that allows any combination of individual 64-Kbyte sectors to be locked down
and become permanently read-only. This addresses the need of certain secure applications that
require portions of the Flash memory array to be permanently protected against malicious
attempts at altering program code, data modules, security information, or encryption/decryption
algorithms, keys, and routines. The device also contains a specialized OTP (One-Time Pro-
grammable) Security Register that can be used for purposes such as unique device
serialization, system-level Electronic Serial Number (ESN) storage, locked key storage, etc.
Specifically designed for use in 3-volt systems, the AT25DF321A supports read, program, and
erase operations with a supply voltage range of 2.7V to 3.6V. No separate voltage is required for
programming and erasing.
2 AT25DF321A [Preliminary]
3686C–DFLASH–12/08