SanDisk SDMB-16-771 Product Manual - Page 44

MultiMediaCard Product Manual ADDRESS_ERROR error bit in the status register, erase. After a range is selected, an individual and while ignoring all further data transfer, wait sector (or group) within that range can be removed (in the Receive-Data-State) for a stop command. using the UNTAG command. The write operation will also be aborted if t h e host tries to write over a write protected area. In this case, however, the card will set t h e WP_VIOLATION bit. Programming of the CSD register does not require a previous block length setting. The transferred data is also CRC protected. Only the least significant 16 bits of the CSD can be changed by the host. The rest of the CSD register content must match the card CSD. If the card detects content inconsistency between the old and new CSD register, it will not reprogram the CSD. This is done to ensure validity of the CRC field of t h e CSD register. After receiving a block of data and completing t h e CRC check, the card will begin programming and hold the DAT line low if its write buffer is full and unable to accept new data from a new WRITE_BLOCK command. The host may poll t h e status of the card with a SEND_STATUS command at any time, and the card will respond with its status. The status bit READY_FOR_DATA indicates whether the MultiMediaCard can accept new data or whether the write process is still in progress. The host may deselect the card by issuing CMD7 (to select a different card) which will place the card in t h e Disconnect State and release the DAT line without interrupting the write operation. When reselecting the card, it will reactivate busy indication by pulling DAT to low if programming is still in progress and write buffer is unavailable. The host must adhere to the following command sequence: TAG_SECTOR_START, TAG_SECTOR_END, UNTAG_SECTOR (up to 16 untag sector commands can be sent for one erase cycle) and ERASE (or the same sequence for group tagging). The following exception conditions are detected by the MultiMediaCard: • An erase or tag/untag command is received out of sequence. The card will set t h e ERASE_SEQ_ERROR error bit in t h e status register and reset the whole sequence. • An out of sequence command (except SEND_STATUS) is received. The card will set the ERASE_RESET status bit in the status register, reset the erase sequence and execute the last command. If the erase range includes write protected sectors, they will be left intact and only the non protected sectors will be erased. The WP_ERASE_SKIP status bit in the status register will be set. The address field in the tag commands is a sector or a group address in byte units. The card will ignore all LSBs below the group or sector size. The number of untag commands (CMD34 and CMD37) which are used in a sequence is limited up to 16. As described above for block write, t h e MultiMediaCard will indicate that an erase is in progress by holding DAT low. • Erase It is desirable to erase many sectors simultaneously in order to enhance the data throughput. Identification of these sectors is accomplished with the TAG_* commands. Either an arbitrary set of sectors within a single erase group, or an arbitrary selection of erase groups may be erased at one time, but not both together. That is, the unit of measure for determining an erase is either a sector or an erase group, but if a sector, all selected sectors must lie within t h e same erase group. To facilitate selection, a first command with the starting address is followed by a second command with the final address, and a l l sectors within this range will be selected for • Write Protect Management Card data may be protected against either erase or write by the write protection features. The entire card may be permanently write protected by the manufacturer or content provider by setting the permanent or temporary write protect bits in the CSD. Portions of the data may also be protected (in units of WP_GRP_SIZE sectors as specified in the CSD). The SET_WRITE_PROT command sets the write protection of t h e addressed write-protect group, and t h e CLR_WRITE_PROT command clears the write protection of the addressed write-protect group. 44 SanDisk MultiMediaCard Product Manual Rev. 2 © 2000 SANDISK CORPORATION