SanDisk SD Card

Revision 2.2Chapter 4 – SD Card Protocol DescriptionSanDisk SD Card Product Manual4.4.5 Erasewhether the write process is still in progress). The host may deselect the card by issuingCMD7 (to select a different card) that will displace the card into the Disconnect State andrelease the DAT line without interrupting the write operation. When reselecting the card, itwill reactivate busy indication by pulling DAT to low if programming is still in progressand the write buffer is unavailable. Actually, the host may perform simultaneous writeoperation to several cards with inter-leaving process. The interleaving process can be doneby accessing each card separately while other cards are busy. This process can be done byproper CMD and DAT0-3 line manipulations (disconnection of busy cards).Send Number of Written BlocksSystems that use the PipeLine mechanism for data buffers management are, in some cases,unable to determine which block was the last to be well written to the flash if an erroroccurs in the middle of a Multiple Blocks Write operation. The card will respond toACMD22 with the number of well-written blocks.Identification of write blocks is accomplished with the ERASE_WR_BLK_START(CMD32), ERASE_WR_BLK_END (CMD33) commands.The host must adhere to the following command sequence: ERASE_WR_BLK_START,ERASE_WR_BLK_END and ERASE (CMD38).If an erase (CMD38) or address setting (CMD32, 33) command is received out ofsequence, the card sets the ERASE_SEQ_ERROR bit in the Status Register and reset theentire sequence.If an out-of-sequence command (except SEND_STATUS) is received, the card will set theERASE_RESET status bit in the Status Register, reset the erase sequence and execute thelast command.If the erase range includes write-protected sectors, they will be left intact and only theunprotected sectors will be erased. The WP_ERASE_SKIP status bit in the Status Registerwill be set.The address field in the address setting commands is a write block address in byte units.The card ignores all LSBs below the WRITE_BLK_LEN (see CSD) size.As described above for block write, the card will indicate that an erase is in progress byholding DAT0 low. The actual erase time may be long, and the host may issue CMD7 tode-select the card or perform card disconnection, as described in the Block Write section,above.The card data after an erase operation is either “0” or “1”, depending on the card vendor.The SCR register bit DATA_STAT_AFTER_ERASE (bit 55) defines whether it is “0” or“1”.4.4.6 Write Protect ManagementThree write-protect methods are supported in the SD Card as follows.• Mechanical write-protect switch (host responsibility only)• Card internal write-protect (card’s responsibility)• Password protection card-lock operation© 2004 SanDisk Corporation 4-11 12/08/04