D640D90VF datasheet(20/54 Pages) AMD

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Am29DL640D

December 13, 2005

Secured Silicon Sector

Flash Memory Region

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 is 256 bytes in length, and

uses a Secured Silicon Sector Indicator Bit (DQ7) to

indicate whether or not the Secured Silicon Sector is

locked when shipped from the factory. This bit is per-

manently 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.

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 per manently set to a “1.” The cus-

tomer-lockable version is shipped with the Secured

Silicon Sector unprotected, allowing customers to uti-

lize the that sector 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 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 Secured Silicon Sector is enabled.

The system accesses the Secured Silicon Sector Se-

cure through a command sequence (see Enter/Exit

Secured Silicon Sector Command Sequence). After

the system has written the Enter Secured Silicon Sec-

tor command sequence, it may read the Secured

Silicon Sector by using the addresses normally occu-

pied by the boot sectors. This mode of operation

continues until the system issues the Exit Secured Sil-

icon Sector command sequence, or until power is

removed from the device. On power-up, or following a

hardware reset, the device reverts to sending com-

mands to the first 256 bytes of Sector 0. Note that the

ACC function and unlock bypass modes are not avail-

able when the Secured Silicon Sector is enabled.

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 preprogrammed with both a ran-

dom number and a secure ESN. The 8-word random

number will at addresses 000000h–000007h in word

mode (or 000000h–00000Fh in byte mode). The se-

cure ESN is 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

through the ExpressFlash service.

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

If the security feature is not required, the Secured Sili-

con Sector can be treated as an additional Flash

memory space. The Secured Silicon Sector can be

read any number of times, but can be programmed

and locked only once. Note that the accelerated pro-

gramming (ACC) and unlock bypass functions are not

available when programming the Secured Silicon

Sector.

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

Figure 2, except that RESET# may be at either VIH

or V

ID. This allows in-system protection of the Se-

cured Silicon Sector Region without raising any de-

vice pin to a high voltage. Note that this method is

only applicable to the Secured Silicon Sector.

To verify the protect/unprotect status of the Secured

Silicon Sector, follow the algorithm shown in

Figure 3.

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 lock must be used with

caution since, once locked, there is no procedure

available for unlocking the Secured Silicon Sector area

and none of the bits in the Secured Silicon Sector

memory space can be modified in any way.

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