AM29DS323D datasheet(22/56 Pages) AMD

22 / 56 page

Am29DS323D

23480A5 October 10, 2006

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 64 Kbytes in length, and

uses a Secured Silicon Sector Indicator Bit 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 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 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-loc k ab le v e rsio n is s h ipped with the

unprotected, allowing customers to utilize the that sec-

tor 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 customer-lockable de-

vices from being used to replace devices that are

factory locked.

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”). After the system has written

the Enter Secured Silicon Sector command sequence,

it may read the Secured Silicon Sector by using the

addresses normally occupied by the boot sectors. 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 reset, the device re-

ver ts to sending commands to the boot sectors

instead of the Secured Silicon sector.

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 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.

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

ha v e

th e

1 6 - b yte

ESN

ad dre sse s

00 00 00 h– 00 000 7h

w o rd

m o d e

(o r

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

vice the starting address of the ESN will be at ad-

dresses 1F83 C0h–1F83 C7h in wo rd mode (or

addresses 3F0780h–3F078Fh 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 permanently locked. Contact an AMD

representative for details on using AMD’s Express-

Flash 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, expanding the size of the available

Flash array by 64 Kbytes. The Secured Silicon Sector

can be read, programmed, and erased as often as re-

quired. 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# may be at either V

IH or

ID. This allows in-system protection of the without

raising any device pin to a high voltage. Note that

this method is only applicable to the Secured Silicon

Sector.

■ Write the three-cycle Enter Secured Silicon Sector

Region command sequence, and then use the alter-

nate method of sector protection described in the

“Sector/Sector Block Protection and Unprotection”.

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 protection must be used

with caution since, once protected, there is no proce-

dure available for unprotecting the Secured Silicon

Sector area and none of the bits in the Secured Silicon

Sector memory space can be modified in any way.

Hardware Data Protection

The command sequence requirement of unlock cycles

for programming or erasing provides data protection

against inadvertent writes (refer to Table 14 for com-

mand definitions). In addition, the following hardware

data protection measures prevent accidental erasure

or programming, which might otherwise be caused by

spurious system level signals during V

CC power-up

and power-down transitions, or from system noise.

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