AM29LV640MT110REF datasheet(25/66 Pages) AMD

25 / 66 page

February 1, 2007 26190C8

Am29LV640MT/B

D A TA

SH EET

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 128 words/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 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.

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 pro-

gram the sector after receiving the device. The cus-

tomer-lockable version also 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 de-

vices that are factory locked.

The Secured Silicon sector address space in this de-

vice is allocated as follows:

The system accesses the Secured Silicon Sector

through a command sequence. See Enter Secured

Sil i con Sector/Exit Secured Si licon Sector

Command Sequence on page 28 After the system has

written the Enter Secured Silicon Sector command se-

quence, it can read the Secured Silicon Sector by

using the addresses normally occupied by the first

sector (SA0). 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 re-

set, the device reverts to sending commands to sector

SA0. Note that the ACC function and unlock bypass

modes are not available when the Secured Silicon

Sector is enabled.

Factory Locked: Secured Silicon Sector

Programmed and Protected At the Factory

In devices with an ESN, the Secured Silicon Sector is

protected when the device is shipped from the factory.

The Secured Silicon Sector cannot be modified in any

way. See Table 7 for Secured Silicon Sector address-

ing.

Customers can opt to have their code programmed by

AMD through the AMD ExpressFlash service. The de-

vices are then shipped from AMD’s factory with the

Secured Silicon Sector permanently locked. Contact

an AMD representative for details on using AMD’s Ex-

pressFlash service.

Customer Lockable: Secured Silicon Sector NOT

Programmed or Protected At the Factory

As an alternative to the factory-locked version, the de-

vice can be ordered such that the customer can pro-

gram and protect the 128-word/256 bytes Secured

Silicon sector.

The system can program the Secured Silicon Sector

using the write-buffer, accelerated and/or unlock by-

pass methods, in addition to the standard program-

ming command sequence. See Command Definitions

on page 27

Programming and protecting the Secured Silicon Sec-

tor must be used with caution since, once protected,

there is no procedure available for unprotecting the

Secured Silicon Sector area and none of the bits in the

Secured Silicon Sector memory space can be modi-

fied in any way.

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# can be at either V

IH or

ID. This allows in-system protection of the Secured

Silicon Sector without raising any device pin to a

high voltage. Note that this method is only applica-

ble to the Secured Silicon Sector.

■ To verify the protect/unprotect status of the Secured

Silicon Sector, follow the algorithm shown in Figure

Once the Secured Silicon Sector is programmed,

locked and verified, the system must write the Exit Se-

cured Silicon Sector Region command sequence to

return to reading and writing within the remainder of

the array.

Table 7.

Secured Silicon Sector Contents

Secured Silicon Sector

Address Range

Standard

Factory

Locked

ExpressFlash

Factory Locked

Customer

Lockable

x16

000000h–

000007h

000000h–

00000Fh

ESN

ESN or

determined

by customer

Determined

by customer

000008h–

00007Fh

000010h–

0000FFh

Unavailable

Determined

by customer

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