D162DB12UI datasheet(21/57 Pages) AMD

21 / 57 page

May 26, 2004

Am29DL16xD

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 uses an Indicator Bit (DQ7)

to indicate whether or not the 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 secu-

rity of the ESN once the product is shipped to the field.

Current version of device has 64 Kbytes; future

versions will have only 256 bytes. This should be

considered during system design.

AMD offers the device with the SecSi Sector either

fa ct o r y lo cke d o r cu sto m e r lo ck a ble. Th e fa c-

tory-locked version is always protected when shipped

from the factory, and has the SecSi Sector Indicator

Bit permanently set to a “1.” The customer-lockable

version is shipped with the unprotected, allowing cus-

tomers to utilize the that sector in any manner they

choose. The customer-lockable version has the SecSi

Sector Indicator Bit permanently set to a “0.” Thus, the

SecSi Sector Indicator Bit prevents customer-lockable

devices from being used to replace devices that are

factory locked.

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

addresses 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

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

have the 16-byte ESN in the lowest addressable mem-

ory area at addresses 00000h–00007h in word mode

(or 000000h–00000Fh in byte mode). In the Top Boot

device the starting address of the ESN will be at the

bottom of the lowest 8 Kbyte boot sector at addresses

F8000h–F8007h in word mode (or 1F0000h–1F000Fh

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 Flash memory space,

expanding the size of the available Flash array. Current

version of device has 64 Kbytes; future versions

will have only 256 bytes. This should be consid-

ered during system design. The SecSi Sector can be

read, programmed, and erased as often as required.

(

Note that in upcoming versions of this device, the

SecSi Sector erase function will not be available.) 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 VIH or VID. 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 SecSi Sector.

■ Write the three-cycle Enter SecSi Sector Region

command sequence, and then use the alternate

method of sector protection described in the “Sec-

tor/Sector Block Protection and Unprotection”.

Once the SecSi Sector is locked and verified, the sys-

t e m mu st writ e t h e E x it SecS i Se ct or Reg i o n

command 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

available for unprotecting the SecSi Sector area and

none of the bits in the SecSi 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

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