AM29DL640D120 AMD [Advanced Micro Devices], AM29DL640D120 Datasheet - Page 19

• Manufacturer Part Number: AM29DL640D120
• Description: 64 Megabit CMOS 3.0 Volt-only, Simultaneous Read/Write Flash Memory
• Manufacturer: AMD [Advanced Micro Devices]

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 secu-
rity of the ESN once the product is shipped to the field.
AMD offers the device with the SecSi Sector either
fac t or y l ocke d or c u s t om e r l o ck abl e. T he 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
Sector unprotected, allowing customers to utilize the
that sector in any manner they choose. The cus-
tomer-lockable version has the SecSi (Secured
Silicon) Sector Indicator Bit permanently set to a “0.”
Thus, the SecSi Sector Indicator Bit prevents cus-
tomer-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 system accesses the SecSi Sector Secure
through a command sequence (see “Enter SecSi™
Sector/Exit SecSi Sector Command Sequence”). After
the system has written the Enter SecSi Sector com-
mand sequence, it may read the SecSi Sector by
using the addresses normally occupied by the boot
sectors. This mode of operation continues until the
system issues the Exit SecSi Sector command se-
quence, 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 first 256 bytes of
Sector 0. Note that the ACC function and unlock by-
pass modes are not available when the SecSi Sector
is enabled.
Factory Locked: SecSi Sector Programmed and
Protected At the Factory
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 preprogrammed with both a random number
and a secure ESN. The 8-word random number will at
addresses 000000h–000007h in word mode (or
18
Am29DL640D
000000h–00000Fh in byte mode). The secure ESN
will be programmed in the next 8 words at addresses
000008h–00000Fh (or 000010h–000020h in byte
mode). The device is available preprogrammed with
one of the following:
■ A random, secure ESN only
■ Customer code through the ExpressFlash service
■ Both a random, secure ESN and customer code
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.
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 Flash memory space.
The SecSi Sector can be read any number of times,
but can be programmed and locked only once. Note
that the accelerated programming (ACC) and unlock
bypass functions are not available when programming
the SecSi Sector.
The SecSi Sector area can be protected using one of
the following procedures:
■ Write the three-cycle Enter SecSi Sector Region
■ To verify the protect/unprotect status of the SecSi
Once the SecSi Sector is locked and verified, the sys-
t e m mu s t w r i t e th e E xi t S e cS i S e ct o r R e g i o n
command sequence to return to reading and writing
the remainder of the array.
The SecSi Sector lock must be used with caution
since, once locked, there is no procedure available for
unlocking the SecSi Sector area and none of the bits
in the SecSi Sector memory space can be modified in
any way.
through the ExpressFlash service.
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
allows in-system protection of the SecSi Sector Re-
gion without raising any device pin to a high voltage.
Note that this method is only applicable to the SecSi
Sector.
Sector, follow the algorithm shown in Figure 3.
October 7, 2004
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or V
ID
. This