SecSiTM (Secured Silicon) Sector
Flash Memory Region
In devices that have an ESN, a Bottom Boot device will
have the 16-byte ESN at addresses
000000h–000007h
in
word
mode
(or
The SecSi (Secured Silicon) Sector feature provides a
256-byte Flash memory region that enables perma-
nent part identification through an Electronic Serial
Number (ESN). The SecSi Sector 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.
000000h–00000Fh in byte mode). In the Top Boot de-
vice the ESN will be at addresses
1FF000h–1FF007Fh in word mode (or addresses
3FE000h–3FE0FFh in byte mode).
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 SecSi Sector permanently locked.
Contact an AMD representative for details on using
AMD’s ExpressFlash service.
AMD offers the device with the SecSi Sector either
factory locked or customer lockable. The fac-
tory-locked version is always protected when shipped
from the factory, and has the SecSi (Secured Silicon)
Sector Indicator Bit permanently set to a “1.” The cus-
tomer-lockable version is shipped with the SecSi Sec-
tor unprotected, allowing customers to utilize the that
sector in any manner they choose. The customer-lock-
able version has the SecSi (Secured Silicon) Sector
Indicator Bit permanently set to a “0.” Thus, the SecSi
Sector Indicator Bit prevents customer-lockable de-
vices from being used to replace devices that are fac-
tory locked.
Customer Lockable: SecSi Sector NOT
Programmed or Protected At the Factory
If the security feature is not required, the SecSi Sector
can be treated as an additional 256-byte Flash mem-
ory space, expanding the size of the available Flash
array. Additionally, note the difference in the loca-
tion of the ESN compared to previous Am29DL32x
top boot factory locked devices. The SecSi Sector
is one-time programmable, may not be erased, and
can be locked only once. Note that the accelerated
programming (ACC) and unlock bypass functions are
not available when programming the SecSi Sector.
The system accesses the SecSi Sector through a
command sequence (see “Enter SecSiTM Sector/Exit
SecSi Sector Command Sequence”). After the system
has written the Enter SecSi Sector command se-
quence, it may read the SecSi Sector by using the ad-
dresses normally occupied by the boot sectors. This
mode of operation continues until the system issues
the Exit SecSi Sector command sequence, or until
power is removed from the device. On power-up, or
following a hardware reset, the device reverts to send-
ing commands to the boot sectors.
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 VIH or VID. This
allows in-system protection of the SecSi Sector
without raising any device pin to a high voltage.
Note that this method is only applicable to the SecSi
Sector
Factory Locked: SecSi Sector Programmed and
Protected At the Factory
■ To verify the protect/unprotect status of the SecSi
Sector, follow the algorithm shown in Figure 3.
In a factory locked device, the SecSi Sector is pro-
tected when the device is shipped from the factory.
The SecSi Sector cannot be modified in any way. The
device is available preprogrammed with one of the fol-
lowing:
Once the SecSi Sector is locked and verified, the sys-
tem must write the Exit SecSi Sector Region com-
mand sequence to return to reading and writing the
remainder of the array.
The SecSi Sector protection must be used with cau-
tion since, once protected, there is no procedure avail-
able for unprotecting the SecSi Sector area and none
of the bits in the SecSi 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.
20
Am29DL320G
September 27, 2004
SPANSION [ SPANSION ]
