S29PL-J SPANSION [SPANSION], S29PL-J Datasheet - Page 49

• Manufacturer Part Number: S29PL-J
• Description: CMOS 3.0 Volt-only, Simultaneous-Read/Write Flash Memory with Enhanced VersatileIO Control
• Manufacturer: SPANSION [SPANSION]

13. Password Protection Mode
13.1
13.2
September 22, 2006 S29PL-J_00_A9
Password and Password Mode Locking Bit
64-bit Password
The Password Sector Protection Mode method allows an even higher level of security than the Persistent
Sector Protection Mode. There are two main differences between the Persistent Sector Protection and the
Password Sector Protection Mode:
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 writing a unique 64-bit Password to the device.
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 password is permanently set with no means to read,
program, 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.
In order to select the Password sector protection scheme, the customer must first program the password. 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 region, the customer may perform Password Verify operations.
Once the desired password is programmed in, the customer must then set the Password Mode Locking Bit.
This operation achieves two objectives:
Permanently sets the device to operate using the Password Protection Mode. It is not possible to reverse this
function.
Disables all further commands to the password region. All program, and read operations are ignored.
Both of these objectives are important, and if not carefully 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 Locking Bit is disabled from programming, guaranteeing that
no changes to the protection scheme are allowed.
The 64-bit Password is located in its own memory space and is accessible through the use of the Password
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 command
from reading the contents of the password on the pins of the device.
D a t a
S h e e t
( A d v a n c e
S29PL-J
I n f o r m a t i o n )
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