BS640HD9V datasheet(25/89 Pages) AMD

25 / 89 page

May 10, 2006 27024B3

Am29BDS128H/Am29BDS640H

D A TA

SH EE T

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 128-word SecSi sector is divided into 64

factory-lockable words that can be programmed and

locked by the customer. The SecSi sector is located at

addresses 000000h-00007Fh in both Persistent Pro-

tection mode and Password Protection mode. It uses

in dicato r b its (DQ 6 , DQ7) to indicate t he fa c-

tory-locked and customer-locked status of the part.

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 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 normal address space.

Factory-Locked Area (64 words)

T he fa cto r y- locke d ar ea of t h e SecSi Se ct o r

(000000h-00003Fh) is locked when the par t is

shipped, whether or not the area was programmed at

the factory. The SecSi Sector Factory-locked Indicator

Bit (DQ7) is permanently set to a “1”. AMD offers the

ExpressFlash service to program the factory-locked

area with a random ESN, a customer-defined code, or

any combination of the two. Because only AMD can

program and protect the factory-locked area, this

method ensures the security of the ESN once the

product is shipped to the field. Contact an AMD repre-

sentative for details on using the AMD ExpressFlash

service.

Table 7.

SecSiTM Sector Addresses

Customer-Lockable Area (64 words)

The customer-lockable area of the SecSi Sector

(000040h-00007Fh) is shipped unprotected, which al-

lows the customer to program and optionally lock the

area as appropriate for the application. The SecSi

Sector Customer-locked Indicator Bit (DQ6) is shipped

as “0” and can be permanently locked to “1” by issuing

the SecSi Protection Bit Program Command. The

SecSi Sector can be read any number of times, but

can be programmed and locked only once. Note that

the accelerated programming (ACC) and unlock by-

pass functions are not available when programming

the SecSi Sector.

The Customer-lockable SecSi Sector area can be pro-

tected 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 Re-

gion 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 Secure

Region command sequence, and then use the alter-

nate method of sector protection described in the

High Voltage Sector Protection section.

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 lock must be used with caution

since, once locked, there is no procedure available for

unlocking the SecSi Sector area and none of the bits

in the SecSi Sector memory space can be modified in

any way.

SecSi Sector Protection Bits

The SecSi Sector Protection Bits prevent program-

ming of the SecSi Sector memory area. Once set, the

SecSi Sector memory area contents are non-modifi-

able.

Hardware Data Protection

The command sequence requirement of unlock cycles

for programming or erasing provides data protection

against inadvertent writes (refer to Table 20, “Memory

Array Command Definitions,” on page 46 for command

definitions).

The device offers two types of data protection at the

sector level:

■ The PPB and DYB associated command se-

quences disables or re-enables both program and

erase operations in any sector or sector group.

■ When WP# is at VIL, the four outermost sectors are

locked.

■ When ACC is at VIL, all sectors are locked.

The following hardware data protection measures

prevent accidental erasure or programming, which

might otherwise be caused by spurious system level

signals during VCC power-up and power-down transi-

tions, or from system noise.

Sector Size

Address Range

Am29BDS128H/

Am29BDS640H

128 words

000000h–00007Fh

Factory-Locked Area

64 words

000000h–00003Fh

Customer-Lockable Area

64 words

000040h–00007Fh

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