AM29LV640MH datasheet(22/62 Pages) AMD

22 / 62 page

Am29LV640MH/L

December 14, 2005

DA TA SH EET

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 128 words/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 pre-

vents 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 SecSi Sector either

fa ctor y locked o r custo m er lock able. The fa c-

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 program the

sector after receiving the device. The customer-lock-

able version also has the SecSi Sector Indicator Bit

permanently set to a “0.” Thus, the SecSi Sector Indi-

cator Bit prevents customer-lockable devices from

being used to replace devices that are factory locked.

The SecSi sector address space in this device is allo-

cated as follows:

The system accesses the SecSi Sector through a

command sequence (see “Enter SecSi 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 first sector (SA0).

This mode of operation continues until the system is-

sues 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

sending commands to sector SA0.

Factory Locked: SecSi Sector Programmed and

Protected At the Factory

In devices with an ESN, the SecSi Sector is protected

when the device is shipped from the factory. The SecSi

Sector cannot be modified in any way. See Table 5 for

SecSi Sector addressing.

Customers may 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

SecSi Sector permanently locked. Contact an AMD

representative for details on using AMD’s Express-

Flash service.

Customer Lockable: SecSi Sector NOT

Programmed or Protected At the Factory

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

vice may be ordered such that the customer may pro-

gram and protect the 128-word/256 bytes SecSi

sector. See Table 5 for SecSi Sector addressing.

The system may program the SecSi Sector using the

write-buffer, accelerated and/or unlock bypass meth-

ods, in addition to the standard programming com-

mand sequence. See Command Definitions.

Programming and protecting the SecSi Sector must be

used with caution since, once protected, there is no

procedure available for unprotecting the SecSi Sector

area and none of the bits in the SecSi Sector memory

space can be modified in any way.

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.

■ To verify the protect/unprotect status of the SecSi

Sector, follow the algorithm shown in Figure 3.

Once the SecSi Sector is programmed, locked and

verified, the system must write the Exit SecSi Sector

Region command sequence to return to reading and

writing within the remainder of the array.

SecSi 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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