May 1, 2006 S29GL-N_01_A0
S29GL-N
29
Data
She e t
8.19
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 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 an AMD sales representative for ordering information). The customer-
lockable version is shipped with the Secured Silicon Sector unprotected, allowing customers to program 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.
The Secured Silicon sector address space in this device is allocated as follows:
The system accesses the Secured Silicon Sector through a command sequence (see
Write Protect (WP#)on page 30). After the system has written the Enter Secured 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.
8.19.1
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, accelerated and/or unlock
bypass methods, in addition to the standard programming command sequence. See
Command DefinitionsProgramming and protecting the Secured Silicon Sector must be used with caution 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.
To verify the protect/unprotect status of the Secured Silicon Sector, follow the algorithm.
Once the Secured Silicon Sector is programmed, locked and verified, the system must write the Exit Secured
Silicon Sector Region command sequence to return to reading and writing within the remainder of the array.
Secured Silicon Sector
Address Range
Customer Lockable
ESN Factory Locked
ExpressFlash
Factory Locked
000000h–000007h
Determined by customer
ESN
ESN or determined by customer
000008h–00007Fh
Unavailable
Determined by customer