AM29DL320G datasheet(22/58 Pages) SPANSION

22 / 58 page

Am29DL320G

September 27, 2004

SecSiTM (Secured Silicon) Sector

Flash Memory Region

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.

AMD offers the device with the SecSi Sector either

fa cto r y lo cke d o r cu sto m e r lo cka b le . Th e 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 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.

The system accesses the SecSi Sector through a

command sequence (see “Enter SecSi

TM 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.

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 available preprogrammed with one of the fol-

lowing:

■ A random, secure ESN only

■ Customer code through the ExpressFlash service

■ Both a random, secure ESN and customer code

through the ExpressFlash service.

In devices that have an ESN, a Bottom Boot device will

hav e

the

16 -by t e

ESN

addres s e s

000000 h–000007h

w o rd

mode

(or

000000h–00000Fh in byte mode). In the Top Boot de-

v i ce

the

ESN

w ill

addres ses

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.

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 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 V

IH 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 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.

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