239
Western Digital Hard Disk Drive OEM Specification
11.43 Security Unlock (F2h)
Command Block Output Registers
Command Block Input Registers
Table 208 Security Unlock Command (F2h)
This command unlocks the password and causes the device to enter device unlock mode. If power on reset or hard
reset is done without executing the Security Disable Password command after this command is completed, the
device will be in device lock mode. The password has not been changed yet.
The Security Unlock command requests to transfer a single sector of data from the host including information
specified in Table 208 on the page 239.
If the Identifier bit is set to master and the file is in high security mode then the password supplied will be compared
with the stored master password. If the file is in maximum security mode then the security unlock will be rejected.
If the Identifier bit is set to user, then the file compares the supplied password with the stored user password.
If the password compare fails, then the device returns an abort error to the host and decrements the unlock attempt
counter. This counter is initially set to 5 and is decremented for each password mismatch.
When security is disabled and the Identifier bit is set to User, then the device shall return command aborted.
When this counter reaches zero then all password protected commands are rejected until a hard reset or a power
off.
: Identifier (1-Mater, 0-User)
Table 209 Security Unlock Information
Zero indicates that device regards Password as User Password. One indicates that device regards
Password as Master Password.
The user can detect if the attempt to unlock the device has failed due to a mismatched password as this is the only
reason that an abort error will be returned by the file AFTER the password information has been sent to the device. If
an abort error is returned by the device BEFORE the password data has been sent to the file then another problem
exists.
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