Secured Silicon Sector Flash Memory Region
The Secured Silicon Sector feature provides a Flash memory region that enables
permanent part identification 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 permanently set at the factory
and cannot be changed, which prevents cloning of a factory locked part. This en-
sures the security of the ESN once the product is shipped to the field.
The device is offered with the Secured Silicon Sector either customer lockable
(standard shipping option) or factory locked (contact a sales office or represen-
tative for ordering information). The customer-lockable version is shipped with
the Secured Silicon Sector unprotected, allowing customers to program the sec-
tor after receiving the device. The customer-lockable version also has the
Secured Silicon Sector Indicator Bit permanently set to a “0.” The factory-locked
version is always protected when shipped from the factory, and has the Secured
Silicon Sector Indicator Bit permanently set to a “1.” Thus, the Secured Silicon
Sector Indicator Bit prevents customer-lockable devices from being used to re-
place 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 Secured Silicon sector address space in this device is allocated as follows:
Table 5. Secured Silicon Sector Addressing
Secured Silicon Sector Address
ESN or determined
The system accesses the Secured Silicon Sector through a command sequence
(see “Enter Secured Silicon Sector/Exit Secured Silicon Sector Command Se-
quence”). After the system writes the Enter Secured Silicon Sector command
sequence, it may read the Secured Silicon Sector by using the addresses given
in Table 5. This mode of operation continues until the system issues the Exit Se-
cured Silicon Sector command sequence, or until power is removed from the
device. On power-up, or following a hardware reset, the device reverts to send-
ing commands to sector SA0.
Customer Lockable: Secured Silicon Sector NOT Programmed or
Protected At the Factory
Unless otherwise specified, the device is shipped such that the customer may
program and protect the 256-byte Secured Silicon sector.
The system may program the Secured Silicon Sector using the write-buffer, ac-
celerated and/or unlock bypass methods, in addition to the standard
programming command sequence. See “Command Definitions” on page 23.
Programming and protecting the Secured Silicon Sector must be used with cau-
tion since, once protected, there is no procedure available for unprotecting the
Secured Silicon Sector area and none of the bits in the Secured Silicon Sector
memory space can be modified in any way.
25974B5 January 31, 2007