MX66L51235FMI-10G datasheet(77/83 Pages) MCNIX

77 / 83 page

MX66L51235F

Rev. 1.1, August 02, 2016

P/N: PM1832

9-34-8. SPB Password Protection Mode

The security level of Password Protection Method is higher than the Solid protection mode. The 64 bit password is

requested before modify SPB lock bit status. When device is under password protection mode, the SPB lock bit is

cleared to “0”, after a power-up cycle or Reset Command.

A correct password is required for PASSULK command, to unlock the SPB lock bit. Await 2us is necessary

to unlocked the device after valid password is given. After that, the SPB bits are allows to be changed. The

PASSULK command are issued slower than 2 μs every time, to prevent hacker from trying all the 64-bit password

combinations.

To place the device in password protection mode, a few more steps are required. First, prior to entering the

password protection mode, it is necessary to set a 64-bit password to verify it. Password verification is only

allowed during the password programming operation. Second, the password protection mode is then activated by

programming the Password Protection Mode Lock Bit to clear to ”0”. This operation is not reversible. Once the bit is

programmed, it cannot be erased, and the device remains permanently in password protection mode, and the 64-bit

password can neither be retrieved nor reprogrammed. Moreover, all commands to the address where the password

is stored are disabled.

The password is all “1”s when shipped from the factory, it is only capable of programming "0"s under WRPASS

command. All 64-bit password combinations are valid as a password. No special address is required for

programming the password. The password is no longer readable after the Password Protection mode is selected by

programming Lock register bit 2 to "0".

Once sector under protected status, device will ignores the program/erase command, enable status polling and

returns to read mode without contents change. The DPB, SPB and SPB lock bit status of each sector can be

verified by issuing RDDPB, RDSPB, and RDSPBLK commands.

● The unlock operation may fail if the password provided by PASSULK command does not match the previously

entered password. It causes the same result when a programming operation is performed on a protected sector.

The P_FAIL bit is set to 1 and the WIP Bit remains set.

● It is not allowed to execute the PASSULK command faster than every 100us ± 20us. The reason behind it is to

make it impossible to hack into the system by running through all the combinations of a set of 64-bit password (58

million years). To verify if the device has completed the password unlock command and is available to process

a new password command, the Read Status Register command is needed to read the WIP bit. When a valid

password is provided the password unlock command does not insert the 100us delay before returning the WIP

bit to zero.

● It is not feasible to set the SPB Lock bit if the password is missing after the Password Mode is selected.

Password Register (PASS)

Bits

Field

Name Function Type

Default State

Description

63 to 0 PWD

Hidden

Password OTP FFFFFFFFFFFFFFFFh

Non-volatile OTP storage of 64 bit password. The

password is no longer readable after the password

protection mode is selected by programming Lock

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