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:
SecSi Sector Address
Range
ExpressFlash
Factory Locked
Customer Lockable ESN Factory Locked
ESN or determined by
customer
000000h–000007h
000008h–00007Fh
ESN
Determined by
customer
Determined by
customer
Unavailable
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 or V . This allows in-system protec-
IH
ID
96
S29GLxxxM MirrorBitTM Flash Family
S29GLxxxM_00A5 April 30, 2004
SPANSION [ SPANSION ]
