D A T A S H E E T
can be programmed and locked only once. Note that
SecSi™ (Secured Silicon) Sector
Flash Memory Region
the accelerated programming (ACC) and unlock by-
pass functions are not available when programming
the SecSi Sector.
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
indicator bits (DQ6, DQ7) to indicate the fac-
tory-locked and customer-locked status of the part.
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 V or V . This
IH
ID
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.
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.
■ 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.
Factory-Locked Area (64 words)
The factory-locked area of the SecSi Sector
(000000h-00003Fh) is locked when the part 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.
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).
TM
Table 7. SecSi Sector Addresses
Sector Size
Address Range
The device offers two types of data protection at the
sector level:
Am29BDS128H/
Am29BDS640H
128 words
000000h–00007Fh
■ The PPB and DYB associated command se-
quences disables or re-enables both program and
erase operations in any sector or sector group.
Factory-Locked Area
64 words
64 words
000000h–00003Fh
000040h–00007Fh
Customer-Lockable Area
Customer-Lockable Area (64 words)
■ When WP# is at V , the four outermost sectors are
IL
locked.
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
■ When ACC is at V , all sectors are locked.
IL
The following hardware data protection measures
prevent accidental erasure or programming, which
might otherwise be caused by spurious system level
signals during V
tions, or from system noise.
power-up and power-down transi-
CC
May 10, 2006 27024B3
Am29BDS128H/Am29BDS640H
23
SPANSION [ SPANSION ]
