
96
S29GLxxxM MirrorBit
TM
 Flash Family
S29GLxxxM_00A5  April 30, 2004
P r e l i m i n a r y
SecSi (Secured Silicon) Sector Flash Memory Region
The SecSi (Secured Silicon) Sector feature provides a Flash memory region that 
enables permanent part identification through an Electronic Serial Number 
(ESN). The SecSi Sector is 256 bytes in length, and uses a SecSi Sector Indicator 
Bit (DQ7) to indicate whether or not the SecSi 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 SecSi Sector either customer lockable 
(standard shipping option) or factory locked (contact a Spansion sales represen-
tative for ordering information). The customer-lockable version is shipped with 
the SecSi Sector unprotected, allowing customers to program the sector after re-
ceiving the device. The customer-lockable version also has the SecSi Sector 
Indicator Bit permanently set to a “0.” The factory-locked version is always pro-
tected when shipped from the factory, and has the SecSi (Secured Silicon) Sector 
Indicator Bit permanently set to a “1.” Thus, the SecSi Sector Indicator Bit pre-
vents 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 SecSi Sector is enabled.
The SecSi sector address space in this device is allocated as follows:
The system accesses the SecSi Sector through a command sequence (see “Write 
Protect (WP#)”). After the system has written the Enter SecSi Sector command 
sequence, it may read the SecSi Sector by using the addresses normally occupied 
by the first sector (SA0). This mode of operation continues until the system issues 
the Exit SecSi Sector command sequence, or until power is removed from the de-
vice. On power-up, or following a hardware reset, the device reverts to sending 
commands to sector SA0.
Customer Lockable: SecSi 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 SecSi sector. 
The system may program the SecSi Sector using the write-buffer, accelerated 
and/or unlock bypass methods, in addition to the standard programming com-
mand sequence. See Command Definitions.
Programming and protecting the SecSi Sector must be used with caution since, 
once protected, there is no procedure available for unprotecting the SecSi Sector 
area and none of the bits in the SecSi Sector memory space can be modified in 
any way. 
The SecSi Sector area can be protected using one of the following procedures: 
 Write the three-cycle Enter SecSi Sector Region command sequence, and 
then follow the in-system sector protect algorithm as shown in 
Figure 2
, ex-
cept that 
RESET# may be at either V
IH
 or V
ID
. This allows in-system protec-
SecSi 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