D A T A S H E E T
(or 000000h–00000Fh in byte mode). In the Top Boot
Secured Silicon Sector Flash
Memory Region
device the starting address of the ESN will be at the
bottom of the lowest 8 Kbyte boot sector at addresses
F8000h–F8007h in word mode (or 1F0000h–1F000Fh
in byte mode).
The Secured Silicon Sector feature provides a Flash
memory region that enables permanent part identifica-
tion through an Electronic Serial Number (ESN). The
Secured Silicon Sector uses an Indicator Bit (DQ7) to
indicate whether or not the 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 secu-
rity of the ESN once the product is shipped to the field.
Current version of device has 64 Kbytes; future
versions will have only 256 bytes. This should be
considered during system design.
Customers may opt to have their code programmed by
AMD through the AMD ExpressFlash service. AMD
programs the customer’s code, with or without the ran-
dom ESN. The devices are then shipped from AMD’s
factory with the Secured Silicon Sector permanently
locked. Contact an AMD representative for details on
using AMD’s ExpressFlash service.
Customer Lockable: Secured Silicon Sector NOT
Programmed or Protected At the Factory
AMD offers the device with the Secured Silicon Sector
either factory locked or customer lockable. 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.” The cus-
tomer-lockable version is shipped with the
unprotected, allowing customers to utilize the that sec-
tor in any manner they choose. The customer-lockable
version has the Secured Silicon Sector Indicator Bit
permanently set to a “0.” Thus, the Secured Silicon
Sector Indicator Bit prevents customer-lockable de-
vices from being used to replace devices that are
factory locked.
If the security feature is not required, the Secured Sili-
con Sector can be treated as an additional Flash
memory space, expanding the size of the available
Flash array. Current version of device has 64
Kbytes; future versions will have only 256 bytes.
This should be considered during system design.
The Secured Silicon Sector can be read, programmed,
and erased as often as required. (Note that in upcoming
versions of this device, the Secured Silicon Sector
erase function will not be available.) Note that the ac-
celerated programming (ACC) and unlock bypass
functions are not available when programming the Se-
cured Silicon Sector.
The system accesses the Secured Silicon Sector
through a command sequence (see “Enter Secured
Silicon Sector/Exit Secured Silicon Sector Command
Sequence”). After the system has written the Enter
Secured Silicon Sector command sequence, it may
read the Secured Silicon Sector by using the ad-
dresses normally occupied by the boot sectors. 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 re-
verts to sending commands to the boot sectors.
The Secured Silicon Sector area can be protected using
one of the following procedures:
■ Write the three-cycle Enter Secured Silicon Sector
Region command sequence, and then follow the
in-system sector protect algorithm as shown in Fig-
ure 2, except that RESET# may be at either VIH or
VID. This allows in-system protection of the without
raising any device pin to a high voltage. Note that
this method is only applicable to the Secured Silicon
Sector.
■ Write the three-cycle Enter Secured Silicon Sector
Region command sequence, and then use the alter-
nate method of sector protection described in the
“Sector/Sector Block Protection and Unprotection”.
Factory Locked: Secured Silicon Sector
Programmed and Protected At the Factory
In a factory locked device, the Secured Silicon Sector
is protected when the device is shipped from the fac-
tory. The Secured Silicon Sector cannot be modified in
any way. The device is available preprogrammed with
one of the following:
Once the Secured Silicon Sector is locked and veri-
fied, the system must write the Exit Secured Silicon
Sector Region command sequence to return to read-
ing and writing the remainder of the array.
The Secured Silicon Sector protection must be used
with caution since, once protected, there is no proce-
dure 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.
■ A random, secure ESN only
■ Customer code through the ExpressFlash service
■ Both a random, secure ESN and customer code
through the ExpressFlash service.
In devices that have an ESN, a Bottom Boot device will
have the 16-byte ESN in the lowest addressable mem-
ory area at addresses 00000h–00007h in word mode
Hardware Data Protection
The command sequence requirement of unlock cycles
for programming or erasing provides data protection
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SPANSION [ SPANSION ]
