A d v a n c e I n f o r m a t i o n
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 factory offers the device with the Secured Silicon Sector either customer
lockable (standard shipping option) or factory locked (contact a Spansion sales
representative for ordering information). The customer-lockable version is
shipped with the Secured Silicon Sector unprotected, allowing customers to pro-
gram the sector after receiving the device. The customer-lockable version also
contains the Secured Silicon Sector Indicator Bit permanently set to a 0. 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. Thus, the Se-
cured Silicon Sector Indicator Bit prevents customer-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 Secured Silicon sector address space in this device is allocated as follows:
Secured Silicon Sector Address Range
Standard Factory
Locked
ExpressFlash Factory
Locked
x16
x8
Customer Lockable
ESN or determined by
customer
000000h–000007h
000000h-00000Fh
ESN
Determined by
customer
Determined by
customer
000008h–00007Fh
000010h-0000FFh
Unavailable
The system accesses the Secured Silicon Sector through a command sequence
(see Write Protect (WP#) on page 38). After the system writes the Enter Se-
cured Silicon Sector command sequence, it may read the Secured Silicon Sector
by using the addresses normally occupied by the first sector (SA0). This mode
of operation continues until the system issues the Exit Secured Silicon Sector
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 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 43.
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.
The Secured Silicon Sector area can be protected using one of the following
procedures:
April 22, 2005 S29GL-A_00_A3
S29GL-A MirrorBit™ Flash Family
37
SPANSION [ SPANSION ]
