TS256M~
2GUSD
microSD Memory Card
• NSAC
Defines the worst case for the clock dependent factor of the data access time. The unit for NSAC is100 clock cycles.
Therefore, the maximal value for the clock dependent part of the data access time is 25.5k clock cycles.
The total access time NAC as expressed in the Table 34 is the sum of TAAC and NSAC. It has to be computed by the
host for the actual clock rate. 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
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Transcend Information Inc.
TRANSCEND [ TRANSCEND INFORMATION. INC. ]
