AM29DL640D_05 Datasheet, PDF (20/54 Pages) Advanced Micro Devices – 64 Megabit (8 M x 8-Bit/4 M x 16-Bit) CMOS 3.0 Volt-only, Simultaneous Read/Write Flash Memory

Secured Silicon Sector
Flash Memory Region
The Secured Silicon Sector feature provides a Flash
memory region that enables permanent part identifica-
tion through an Electronic Serial Number (ESN). The
Secured Silicon Sector is 256 bytes in length, and
uses a Secured Silicon Sector Indicator Bit (DQ7) to
indicate whether or not the Secured Silicon Sector is
locked when shipped from the factory. This bit is per-
manently set at the factory and cannot be changed,
which prevents cloning of a factory locked part. This
ensures the security of the ESN once the product is
shipped to the field.
AMD offers the device with the Secured Silicon Sector
either factory locked or customer lockable. The fac-
tory-locked version is always protected when shipped
from the factory, and has the Secured Silicon Sector
Indicator Bit permanently set to a “1.” The cus-
tomer-lockable version is shipped with the Secured
Silicon Sector unprotected, allowing customers to uti-
lize the that sector in any manner they choose. The
customer-lockable version has the Secured Silicon
Sector Indicator Bit permanently set to a “0.” Thus, the
Secured Silicon Sector Indicator Bit prevents cus-
tomer-lockable devices from being used to replace
devices that are factory locked. Note that the ACC
function and unlock bypass modes are not available
when the Secured Silicon Sector is enabled.
The system accesses the Secured Silicon Sector Se-
cure through a command sequence (see Enter/Exit
Secured Silicon Sector Command Sequence). After
the system has written the Enter Secured Silicon Sec-
tor command sequence, it may read the Secured
Silicon Sector by using the addresses normally occu-
pied by the boot sectors. This mode of operation
continues until the system issues the Exit Secured Sil-
icon Sector command sequence, or until power is
removed from the device. On power-up, or following a
hardware reset, the device reverts to sending com-
mands to the first 256 bytes of Sector 0. Note that the
ACC function and unlock bypass modes are not avail-
able when the Secured Silicon Sector is enabled.
Factory Locked: Secured Silicon Sector
Programmed and Protected At the Factory
In a factory locked device, the Secured Silicon Sector
is protected when the device is shipped from the fac-
tory. The Secured Silicon Sector cannot be modified in
any way. The device is preprogrammed with both a ran-
dom number and a secure ESN. The 8-word random
number will at addresses 000000h–000007h in word
mode (or 000000h–00000Fh in byte mode). The se-
cure ESN is programmed in the next 8 words at
addresses 000008h–00000Fh (or 000010h–000020h
in byte mode). The device is available preprogrammed
with one of the following:
„ A random, secure ESN only
„ Customer code through the ExpressFlash service
„ Both a random, secure ESN and customer code
through the ExpressFlash service.
Customers may opt to have their code programmed by
AMD through the AMD ExpressFlash service. AMD
programs the customer’s code, with or without the ran-
dom ESN. The devices are then shipped from AMD’s
factory with the Secured Silicon Sector permanently
locked. Contact an AMD representative for details on
using AMD’s ExpressFlash service.
Customer Lockable: Secured Silicon Sector NOT
Programmed or Protected At the Factory
If the security feature is not required, the Secured Sili-
con Sector can be treated as an additional Flash
memory space. The Secured Silicon Sector can be
read any number of times, but can be programmed
and locked only once. Note that the accelerated pro-
gramming (ACC) and unlock bypass functions are not
available when programming the Secured Silicon
Sector.
The Secured Silicon Sector area can be protected
using one of the following procedures:
„ Write the three-cycle Enter Secured Silicon Sector
Region command sequence, and then follow the
in-system sector protect algorithm as shown in
Figure 2, except that RESET# may be at either V_IH
or V_ID. This allows in-system protection of the Se-
cured Silicon Sector Region without raising any de-
vice pin to a high voltage. Note that this method is
only applicable to the Secured Silicon Sector.
„ To verify the protect/unprotect status of the Secured
Silicon Sector, follow the algorithm shown in
Figure 3.
Once the Secured Silicon Sector is locked and veri-
fied, the system must write the Exit Secured Silicon
Sector Region command sequence to return to read-
ing and writing the remainder of the array.
The Secured Silicon Sector lock must be used with
caution since, once locked, there is no procedure
available for unlocking the Secured Silicon Sector area
and none of the bits in the Secured Silicon Sector
memory space can be modified in any way.
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Am29DL640D
December 13, 2005