AM29LV640MH SPANSION [SPANSION], AM29LV640MH Datasheet - Page 22

• Manufacturer Part Number: AM29LV640MH
• Description: 64 Megabit (4 M x 16-Bit/8 M x 8-Bit) MirrorBit 3.0 Volt-only Uniform Sector Flash Memory with VersatileI/O Control
• Manufacturer: SPANSION [SPANSION]

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 128 words/256 bytes in
length, and uses a SecSi Sector Indicator Bit (DQ7) 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 pre-
vents cloning of a factory locked part. This ensures the
security of the ESN once the product is shipped to the
field.
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 first sector (SA0).
This mode of operation continues until the system is-
sues 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
sending commands to sector SA0.
Factory Locked: SecSi Sector Programmed and
Protected At the Factory
In devices with an ESN, the SecSi Sector is protected
when the device is shipped from the factory. The SecSi
Sector cannot be modified in any way. See
SecSi Sector addressing.
Customers may opt to have their code programmed by
AMD through the AMD ExpressFlash service. The de-
vices are then shipped from AMD’s factory with the
SecSi Sector 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
As an alternative to the factory-locked version, the de-
vice may be ordered such that the customer may pro-
20
000000h–
000008h–
000007h
00007Fh
x16
SecSi Sector Address Range
000000h–
000010h–
00000Fh
0000FFh
x8
Table 5
D A T A S H E E T
Standard Factory
Unavailable
Am29LV640MH/L
Locked
ESN
for
AMD offers the device with the SecSi Sector either
factor y locked o r custo mer lockable. The fac-
tory-locked version is always protected when shipped
from the factory, and has the SecSi (Secured Silicon)
Sector Indicator Bit permanently set to a “1.” The cus-
tomer-lockable version is shipped with the SecSi Sec-
tor unprotected, allowing customers to program the
sector after receiving the device. The customer-lock-
able version also has the SecSi Sector Indicator Bit
permanently set to a “0.” Thus, the SecSi Sector Indi-
cator Bit prevents customer-lockable devices from
being used to replace devices that are factory locked.
The SecSi sector address space in this device is allo-
cated as follows:
gram and protect the 128-word/256 bytes SecSi
sector. See
The system may program the SecSi Sector using the
write-buffer, accelerated and/or unlock bypass meth-
ods, in addition to the standard programming com-
mand sequence. See
Programming and protecting the SecSi Sector must be
used with caution 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.
The SecSi Sector area can be protected using one of
the following procedures:
■ Write the three-cycle Enter SecSi Sector Region
■ To verify the protect/unprotect status of the SecSi
Once the SecSi Sector is programmed, locked and
verified, the system must write the Exit SecSi Sector
Region command sequence to return to reading and
writing within the remainder of the array.
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
allows in-system protection of the SecSi Sector
without raising any device pin to a high voltage.
Note that this method is only applicable to the SecSi
Sector.
Sector, follow the algorithm shown in Figure 3.
ESN or determined
Factory Locked
Table 5
ExpressFlash
by customer
by customer
Determined
for SecSi Sector addressing.
Command
Definitions.
December 14, 2005
Determined by customer
Customer Lockable
IH
or V
ID
. This