S29PL032J SPANSION [SPANSION], S29PL032J Datasheet - Page 55

• Manufacturer Part Number: S29PL032J
• Description: CMOS 3.0 Volt-only, Simultaneous Read/Write Flash Memory with Enhanced VersatileIO Control
• Manufacturer: SPANSION [SPANSION]

Password Protection Mode
April 7, 2005 31107A62
Persistent Sector Protection Mode Locking Bit
Password and Password Mode Locking Bit
If the user attempts to program or erase a protected sector, the device ignores
the command and returns to read mode. A program command to a protected sec-
tor enables status polling for approximately 1 µs before the device returns to read
mode without having modified the contents of the protected sector. An erase
command to a protected sector enables status polling for approximately 50 µs
after which the device returns to read mode without having erased the protected
sector.
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. There is an alter-
native means of reading the protection status. Take RESET# to VIL and hold WE#
at VIH.(The high voltage A9 Autoselect Mode also works for reading the status of
the PPBs). Scanning the addresses (A18–A11) while (A6, A1, A0) = (0, 1, 0) will
produce a logical ‘1” code at device output DQ0 for a protected sector or a “0” for
an unprotected sector. In this mode, the other addresses are don’t cares. Address
location with A1 = VIL are reserved for autoselect manufacturer and device
codes.
Like the password mode locking bit, a Persistent Sector Protection mode locking
bit exists to guarantee that the device remain in software sector protection. Once
set, the Persistent Sector Protection locking bit prevents programming of the
password protection mode locking bit. This guarantees that a hacker could not
place the device in password protection mode.
The Password Sector Protection Mode method allows an even higher level of se-
curity 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
P R E L I M I N A R Y
S29PL127J/S29PL129J/S29PL064J/S29PL032J
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