am41dl3208gt85it Meet Spansion Inc., am41dl3208gt85it Datasheet - Page 25

• Manufacturer Part Number: am41dl3208gt85it
• Description: 32 Mbit 4 M ? 8-bit/2 M ? 16-bit Cmos 3.0 Volt-only, Simultaneous Operation Flash Memory And 8 Mbit 1 M ? 8-bit/512 K ? 16-bit Static Ram Preliminary
• Manufacturer: Meet Spansion Inc.

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 a SecSi Sector Indica-
tor Bit to indicate whether or not the SecSi Sector is
locked when shipped from the factory. This bit is per-
manently 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
f a cto ry lo cked o r cu sto m e r lo cka b le. Th e f a 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 a random, se-
cure ESN only.
In the Top Boot device the ESN will be at addresses
1FF000h–1FF007h in word mode (or addresses
3FE000h–3FE00Fh in byte mode).
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. The
SecSi Sector can be read any number of times, but
can be programmed and locked only once, and cannot
be erased. Note that the accelerated programming
24
P R E L I M I N A R Y
Am41DL3208G
(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:
I Write the three-cycle Enter SecSi Sector Region
I Write the three-cycle Enter SecSi Sector Region
Once the SecSi Sector is locked and verified, the sys-
te m m u st w rit e t h e E xit S e cSi S e c to r R e g io 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 Tables 15 and 16
for command 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
power-up and power-down transitions, or from system
noise.
Low V
When V
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-
quent writes are ignored until V
The system must provide the proper signals to the
control pins to prevent unintentional writes when V
is greater than V
Write Pulse “Glitch” Protection
Noise pulses of less than 5 ns (typical) on OE#, CE#f
or WE# do not initiate a write cycle.
Logical Inhibit
Write cycles are inhibited by holding any one of OE# =
V
IL
, CE#f = V
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 without raising
any device pin to a high voltage. Note that this
method is only applicable to the SecSi Sector.
command sequence, and then use the alternate
method of sector protection described in the “Sec-
tor/Sector Block Protection and Unprotection”.
CC
CC
Write Inhibit
is less than V
IH
or WE# = V
LKO
.
LKO
IH
, the device does not ac-
. To initiate a write cycle,
CC
is greater than V
February 13, 2002
IH
or V
ID
. This
LKO
CC
CC
CC
.