am49pdl127ah Meet Spansion Inc., am49pdl127ah Datasheet - Page 38

• Manufacturer Part Number: am49pdl127ah
• Description: Stacked Multi-chip Package Mcp Flash Memory And Psram, 128 Megabit 8m ? 16-bit Cmos 3.0 Volt-only, Simultaneous Operation Flash Memory And 16 Mbit 1m ? 16-bit Cmos Pseudo Static Ram
• Manufacturer: Meet Spansion Inc.

The programming of the DYB, PPB, and PPB lock for a
given sector can be verified by writing a DYB/PPB/
PPB lock verify command to the device.
Persistent Sector Protection Mode Locking Bit
Like the password mode locking bit, a Persistent Sec-
tor Protection mode locking bit exists to guarantee that
the device remain in software sector protection. Once
set, the Persistent Sector Protection locking bit pre-
vents programming of the password protection mode
locking bit. This guarantees that a hacker could not
place the device in password protection mode.
Password Protection Mode
The Password Sector Protection Mode method allows
an even higher level of security than the Persistent
Sector Protection Mode. There are two main differ-
ences between the Persistent Sector Protection and
the Password Sector Protection Mode:
The Password Sector Protection method is otherwise
identical to the Persistent Sector Protection method.
A 64-bit password is the only additional tool utilized in
this method.
Once the Password Mode Locking Bit is set, the pass-
word is permanently set with no means to read, pro-
gram, or erase it. The password is used to clear the
PPB Lock bit. The Password Unlock command must
be written to the flash, along with a password. The
flash device internally compares the given password
with the pre-programmed password. If they match, the
PPB Lock bit is cleared, and the PPBs can be altered.
If they do not match, the flash device does nothing.
There is a built-in 2 µs delay for each “password
check.” This delay is intended to thwart any efforts to
run a program that tries all possible combinations in
order to crack the password.
Password and Password Mode Locking Bit
In order to select the Password sector protection
scheme, the customer must first program the pass-
word. The password may be correlated to the unique
Electronic Serial Number (ESN) of the particular flash
device. Each ESN is different for every flash device;
therefore each password should be different for every
flash device. While programming in the password re-
gion, the customer may perform Password Verify oper-
ations.
Once the desired password is programmed in, the
customer must then set the Password Mode Locking
Bit. This operation achieves two objectives:
36
When the device is first powered on, or comes out
of a reset cycle, the PPB Lock bit set to the locked
state, rather than cleared to the unlocked state.
The only means to clear the PPB Lock bit is by writ-
ing a unique 64-bit Password to the device.
A D V A N C E
Am49PDL127AH/Am49PDL129AH
I N F O R M A T I O N
1. Permanently sets the device to operate using the
2. Disables all further commands to the password re-
Both of these objectives are important, and if not care-
fully considered, may lead to unrecoverable errors.
The user must be sure that the Password Protection
method is desired when setting the Password Mode
Locking Bit. More importantly, the user must be sure
that the password is correct when the Password Mode
Locking Bit is set. Due to the fact that read operations
are disabled, there is no means to verify what the
password is afterwards. If the password is lost after
setting the Password Mode Locking Bit, there will be
no way to clear the PPB Lock bit.
The Password Mode Locking Bit, once set, prevents
reading the 64-bit password on the DQ bus and further
password programming. The Password Mode Locking
Bit is not erasable. Once Password Mode Locking Bit
is programmed, the Persistent Sector Protection Lock-
ing Bit is disabled from programming, guaranteeing
that no changes to the protection scheme are allowed.
64-bit Password
The 64-bit Password is located in its own memory
space and is accessible through the use of the Pass-
word Program and Verify commands (see “Password
Verify Command”). The password function works in
conjunction with the Password Mode Locking Bit,
which when set, prevents the Password Verify com-
mand from reading the contents of the password on
the pins of the device.
Write Protect (WP#)
The Write Protect feature provides a hardware method
of protecting sectors 0, 1, 268, and 269 in PDL 127 or
in SA1-133, SA1-134, SA2-0, SA2-1 in PDL 129 with-
out using V
and overrides the previously discussed High Voltage
Sector Protection method.
If the system asserts V
vice disables program and erase functions in the two
outermost 4 Kword sectors on both ends of the flash
array independent of whether it was previously pro-
tected or unprotected.
If the system asserts V
vice reverts to whether sectors 0, 1, 268, and 269 in
PDL 127 or in SA1-133, SA1-134, SA2-0, SA2-1 in
PDL 129 were last set to be protected or unprotected.
That is, sector protection or unprotection for these sec-
tors depends on whether they were last protected or
unprotected using the method described in High Volt-
age Sector Protection.
Password Protection Mode. It is not possible to re-
verse this function.
gion. All program, and read operations are ignored.
ID
. This function is provided by the WP# pin
IH
IL
on the WP#/ACC pin, the de-
on the WP#/ACC pin, the de-
December 18, 2003