MultiMediaCardTM
* Setting the Password
- Select a card (CMD7), if not previously selected already
- Define the block length (CMD16), given by the 8bit card lock/unlock mode, the 8-bit password
Size (in bytes), and the number of bytes of the new password. In case that a password
replacement is done, then the block size shall consider that both passwords, the old and the new
one, are sent with the command.
- Send Card Lock/Unlock command with the appropriate data block size on the data line including
16 bit CRC. The data block shall indicate the mode (SET_PWD), the length (PWD_LEN) and the
password itself. In case that a password replacement is done, then the length value (PWD_LEN)
shall include both passwords, the old and the new one, and the PWD field shall include the old
password (currently used) followed by the new password.
In case that the sent old password is not correct (not equal in size and content) then
LOCK_UNLOCK_FAILED error bit will be set in the status register and the old password
password and its size will be saved in the PWD and PWD_LEN fields, respectively.
Note that the password length register (PWD_LEN) indicates if a password is currently set. When it
equals ‘0’ there is no password set. If the value of PWD_LEN is not equal to zero the card will lock
itself after power up. It is possible to lock the card immediately in the current power session by set-
ting the LOCK/UNLOCK bit (while setting the password) or sending additional command for card lock.
* Reset the Password:
- Select a card (CMD7), if not previously selected already
- Define the block length (CMD 16), given by the 8bit card lock/unlock mode, the 8bit password
size (in bytes), and the number of bytes of the currently used password.
- Send the card lock/unlock command with the appropriate data block size on the data line
including 16 bit CRC. The data block shall indicate the mode CLR_PWD, the length (PWD_LEN)
and the password (PWD) itself (LOCK/UNLOCK bit is don’t care). If the PWD and PWD_LEN
content match the sent password and its size, then the content of the PWD register is cleared and
PWD_LEN is set to 0. If the password is not correct then the LOCK_UNLOCK_FAILED error bit
will be set in the status register.
* Locking a card:
- Select a card (CMD7), if not previously selected already
- Define the block length (CMD16), given by the 8 bit card lock/unlock mode, the 8 bit password
size (in bytes), and the number of bytes of the currently used password.
- Send the card lock/unlock command with the appropriate data block size on the data line
including 16 bit CRC. The data block shall indicate the mode LOCK, the length (PWD_LEN) and
the password (PWD) itself.
If the PWD content equals to the sent password then the card will be locked and the card-locked
status bit will be set in the status register. If the password is not correct then
LOCK_UNLOCK_FAILED error bit will be set in the status register. Note that it is possible to set the
password and to lock the card in the same sequence. In such case the host shall perform all the
required steps for setting the password (as described above) including the bit LOCK set while the
new password command is sent. If the password was previously set (PWD_LEN is not ‘0’), then the
card will be locked automatically after power on reset. An attempt to lock a locked card or to lock a
card that does not have a password will fail and the LOCK_UNLOCK_FAILED error bit will be set in
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SAMSUNG [ SAMSUNG ]
