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Document Number: 002-00856 Rev. *E
S29JL064J
8.13
Secured Silicon Region
The Secured Silicon Region feature provides a Flash memory region that enables permanent part identification through an
Electronic Serial Number (ESN). The Secured Silicon Region is 256 bytes in length, and may shipped unprotected, allowing
customers to utilize that sector in any manner they choose, or may shipped locked at the factory (upon customer request). The
Secured Silicon Indicator Bit data will be 81h if factory locked, 41h if customer locked, or 01h if neither. Refer to
for more details.
The system accesses the Secured Silicon Region through a command sequence (see
Enter Secured Silicon Region/Exit Secured
Silicon Region Command Sequence
). After the system has written the Enter Secured Silicon Region command
sequence, it may read the Secured Silicon Region by using the addresses normally occupied by the boot sectors. This mode of
operation continues until the system issues the Exit Secured Silicon Region command sequence, or until power is removed from the
device. On power-up, or following a hardware reset, the device reverts to sending commands to the first 256 bytes of Sector 0.
Note
that the ACC function and unlock bypass modes are not available when the Secured Silicon Region is enabled.
8.13.1
Factory Locked: Secured Silicon Region Programmed and Protected At the
Factory
In a factory locked device, the Secured Silicon Region is protected when the device is shipped from the factory. The Secured Silicon
Region cannot be modified in any way. The device is preprogrammed with both a random number and a secure ESN. The 8-word
random number is at addresses 000000h–000007h in word mode (or 000000h–00000Fh in byte mode). The secure ESN is
programmed in the next 8 words at addresses 000008h–00000Fh (or 000010h–00001Fh in byte mode). The device is available
preprogrammed with one of the following:
A random, secure ESN only
Customer code through Spansion programming services
Both a random, secure ESN and customer code through Spansion programming services
Contact an your local sales office for details on using Spansion programming services.
8.13.2
Customer Lockable: Secured Silicon Region NOT Programmed or Protected At
the Factory
If the security feature is not required, the Secured Silicon Region can be treated as an additional Flash memory space. The Secured
Silicon Region can be read any number of times, but can be programmed and locked only once. Note that the accelerated
programming (ACC) and unlock bypass functions are not available when programming the Secured Silicon Region.
Write the three-cycle Enter Secured Silicon Region command sequence, and then follow the in-system sector protect algorithm as
, except that
RESET# may be at either V
IH
or V
ID
. This allows in-system protection of the Secured
Silicon Region without raising any device pin to a high voltage. Note that this method is only applicable to the Secured Silicon
Region.
To verify the protect/unprotect status of the Secured Silicon Region, follow the algorithm shown in
Once the Secured Silicon Region is locked and verified, the system must write the Exit Secured Silicon Region command sequence
to return to reading and writing the remainder of the array.
The Secured Silicon Region lock must be used with caution since, once locked, there is no procedure available for unlocking the
Secured Silicon Region and none of the bits in the Secured Silicon Region memory space can be modified in any way.