MultiMediaCardTM
the status register.
* Unlocking the 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 UNLOCK, the length (PWD_LEN)
and the password (PWD) itself.
If the PWD content equals to the sent password then the card will be unlocked and the card-locked
status bit will be cleared in the status register. If the password is not correct then the
LOCK_UNLOCK_FAILED error bit will be set in the status register. Note that the unlocking is done
only for the current power session. As long as the PWD is not cleared the card will be locked
automatically on the next power up. The only way to unlock the card is by clearing the password. An
attempt to unlock an unlocked card will fail and LOCK_UNLOCK_FAILED error bit will be set in the
status register.
* Forcing Erase:
In case that the user forgot the password (the PWD content) it is possible to erase all the card data
content along with the PWD content. This operation is called Forced Erase.
- Select a card (CMD7), if not previously selected already.
- Define the block length (CMD16) to 1 byte (8bit card lock/unlock command). Send the card
lock/unlock command with the appropriate data block of one byte on the data line including 16 bit
CRC. The data block shall indicate the mode ERASE (the ERASE bit shall be the only bit set).
If the ERASE bit is not the only bit in the data field then the LOCK_UNLOCK_FAILED error bit will be
set in the status register and the erase request is rejected. If the command was accepted then ALL
THE CARD CONTENT WILL BE ERASED including the PWD and PWD_LEN register content and
the locked card will get unlocked. An attempt to force erase on an unlocked card will fail and
LOCK_UNLOCK_FAILED error bit will be set in the status register.
* State transition summary
Table “Card State Transition Table” defines the card state transitions as a function of received
command
4.9.6 Responses
All responses are sent via command line (CMD), all data starts with the MSB.
Table 4-10 Format R1(Response Command)
0
0
card
bit5 … bit0
command
Bit31 … bit0
status
Bit6 … bit0
CRC
1
start bit
end bit
The contents of the status field are described in Chapter “Status
Format R1b (response command with busy signal):
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