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 can-
not 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.
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
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 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
ESN
Unavailable
ExpressFlash Factory
Locked
ESN or determined by
customer
Determined by customer
x16
000000h–000007h
000008h–00007Fh
x8
000000h-00000Fh
000010h-0000FFh
Customer Lockable
Determined by customer
The system accesses the Secured Silicon Sector through a command sequence
(see “Write Protect (WP#)”). After the system has written the Enter Secured Sil-
icon 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 se-
quence, 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” .
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:
Write the three-cycle Enter Secured Silicon Sector Region command se-
quence, and then follow the in-system sector protect algorithm as shown in
36
S29GLxxxA MirrorBit™ Flash Family
S29GLxxxA_00_A2 January 28, 2005
SPANSION [ SPANSION ]
