Specifications

©Copyright 2001-2013 SD Group (Panasonic, SanDisk, Toshiba) and SD Card Association
Physical Layer Simplified Specification Version 4.10
43
4.3.7.3 Forcing Erase
In the 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 (8-bit card lock/unlock command). Send the card
lock/unlock command with the appropriate data block of one byte on the data line including the
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 set in the data field, 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 be 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.
4.3.7.3.1 Force Erase Function to the Locked Card
Table 4-8
clarifies the relation between force erase and Write Protection. The force erase does not
erase the secure area. The card shall keep its locked state during the erase execution and change to
the unlocked state after the erase of all user area is completed. Similarly, the card shall keep Temporary
and Group Write Protection during the erase execution and clear Write Protection after the erase of all
user area is completed. In the case of an erase error occurs, the card can continue force erase if the
data of error sectors are destroyed.
CMD42 Parameter
PWP
TWP
Result of the Function
Card Status
Bit3
Bit2
Bit1
Bit0
GWP
Bit25
Bit24
1
0
0
0
Yes
don't
care
Error (Note *2 Refer to Table 4-10)
1
1
1
0
0
0
No
Yes
Execute force erase and clear Temporary Write
Protect and Group Write
Protect. (Note *3 Refer to
Table 4-10)
1 to 0
0
1
0
0
0
No
No
Execute force erase.
1 to 0
0
Table 4-8: Force Erase Function to the Locked Card (Relation to the Write Protects)
Write Protections
PWP: Permanent Write Protect (CSD Bit13)
TWP: Temporary Write Protect (CSD Bit12)
GWP: Group Write Protect (CMD28, CMD29, CMD30)