s71ws512ne0bfwzz Meet Spansion Inc., s71ws512ne0bfwzz Datasheet - Page 33

• Manufacturer Part Number: s71ws512ne0bfwzz
• Description: Stacked Multi-chip Product Mcp Flash Memoy And Psram Cmos 1.8 Volt, Simultaneous Operation, Burst Mode Flash Memory And Pseudo-static Ram
• Manufacturer: Meet Spansion Inc.

June 28, 2004 S71WS512NE0BFWZZ_00_A1
Password Sector Protection
tected sector enables status polling and returns to read mode without having
modified the contents of the protected sector.
The programming of the DYB, PPB, and PPB Lock for a given sector can be verified
by writing individual status read commands DYB Status, PPB Status, and PPB
Lock Status to the device.
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 Mode and the Password Sector Protec-
tion 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.
The password is stored in a one-time programmable (OTP) region of the flash
memory. Once the Password Mode Lock 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 1 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.
64-bit Password
The 64-bit Password is located in its own memory space and is accessible through
the use of the Password Program and Verify commands. The password function
works in conjunction with the Password Mode Locking Bit, which when set, pre-
vents the Password Verify command from reading the contents of the password
on the pins of the device.
Persistent Protection Bit Lock (PPB Lock Bit) in Password Sector
Protection Mode
The Persistent Protection Bit Lock (PPB Lock Bit) is a volatile bit that reflects the
state of the Password Mode Lock Bit after power-up reset. If the Password Mode
Lock Bit is also set, after a hardware reset (RESET# asserted) or a power-up re-
set, the ONLY means for clearing the PPB Lock Bit in Password Protection Mode is
to issue the Password Unlock command. Successful execution of the Password
Unlock command to enter the entire password clears the PPB Lock Bit, allowing
for sector PPBs modifications. Asserting RESET# or taking the device through a
power-on reset, resets the PPB Lock Bit to a “1”.
If the Password Mode Lock Bit is not set (device is operating in the default Per-
sistent Protection Mode). The Password Unlock command is ignored in Persistent
Sector Protection Mode.
When the device is first powered up, or comes out of a reset cycle, the PPB
Lock Bit is 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 Pass-
word to the device.
A d v a n c e
S29WSxxxN MirrorBit™ Flash Family For Multi-chip Products (MCP)
I n f o r m a t i o n
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