User manual TRANSCEND MICROSD CARD DATASHEET

[. . . ] However, Transcend makes no warranty, either expressed or implied, as to its accuracy and assumes no liability in connection with the use of this product. Transcend reserves the right to make changes in specifications at any time without prior notice. Transcend Information Inc. 7 TS256M~2GUSD Register Information microSD Memory Card Within the card interface six registers are defined: OCR, CID, CSD, RCA, DSR and SCR. These can be accessed only by corresponding commands (see Chapter 4. 7). [. . . ] The total access time NAC as expressed in the Table 34 is the sum of TAAC and NSAC. The read access time should be interpreted as a typical delay for the first data bit of a data block or stream. · TRAN_SPEED The following table defines the maximum data transfer rate per one data line - TRAN_SPEED: Note that for current SD Memory Cards that field must be always 0_0110_010b (032h) which is equal to 25MHz - the mandatory maximum operating frequency of SD Memory Card. In High-Speed mode, that field must be always 0_1011_010b (05Ah) which is equal to 50MHz. And when the timing mode returns to the default by CMD6 or CMD0 command, its value will be 032h. · CCC The SD Memory Card command set is divided into subsets (command classes). The card command class register CCC defines which command classes are supported by this card. A value of `1' in a CCC bit means that the corresponding Transcend Information Inc. 12 TS256M~2GUSD command class is supported. microSD Memory Card · READ_BL_LEN The maximum read data block length is computed as 2READ_BL_LEN. The maximum block length might therefore be in the range 512. . . 2048 bytes (see Chapter 4. 11 for details). Note that in SD Memory Card the WRITE_BL_LEN is always equal to READ_BL_LEN · READ_BL_PARTIAL (always = 1 in SD Memory Card) Partial Block Read is always allowed in SD Memory Card. The minimum block size will be one byte. · WRITE_BLK_MISALIGN Defines if the data block to be written by one command can be spread over more than one physical block of the memory device. WRITE_BLK_MISALIGN=0 signals that crossing physical block boundaries is invalid. If ERASE_BLK_EN = '0', the host can erase one or multiple units of SECTOR_SIZE. The erase will start from the beginning of the sector that contains the start address to the end of the sector that contains the end address. For example, if SECTOR_SIZE=31 and the host sets the Erase Start Address to 5 and the Erase End Address to 40. If ERASE_BLK_EN = '1' the host can erase one or multiple units of 512 bytes. All blocks that contain data from start address to end address are erased. For example, if the host sets the Erase Start Address to 5 and the Erase End Address to 40. · SECTOR_SIZE The size of an erasable sector. The contents of this register is a 7 bit binary coded value, defining the number of write Transcend Information Inc. 15 TS256M~2GUSD microSD Memory Card blocks (see WRITE_BL_LEN). [. . . ] It can be optionally used to improve the bus performance for extended operating conditions (depending on parameters like bus length, transfer rate or number of Transcend Information Inc. 19 TS256M~2GUSD 6. The CSD register carries the information about the DSR register usage. The default value of the DSR register is 0x404. In addition to the CSD register there is another configuration register that named - SD CARD Configuration Register (SCR). [. . . ]