AM29DL16XC datasheet(17/51 Pages) AMD

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Am29DL16xC

P R E L I M I NARY

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 64 Kbytes in length, and

uses a SecSi Sector Indicator Bit 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 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:

s A random, secure ESN only

s Customer code through the ExpressFlash service

s 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 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

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 by 64

Kbytes. The SecSi Sector can be read, programmed,

and erased as often as required. The SecSi Sector area

can be protected using one of the following procedures:

s 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 without raising

any device pin to a high voltage. Note that this

method is only applicable to the SecSi Sector.

s 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

spurious system level signals during V

CC power-up

and power-down transitions, or from system noise.

Low VCC Write Inhibit

When V

CC is less than VLKO, the device does not ac-

cept any write cycles. This protects data during V

power-up and power-down. The command register

and all internal program/erase circuits are disabled,

and the device resets to reading array data. Subse-

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