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Exchanges between the host and card begin with a command (sent by the host on the CMD line), often followed by a response from the card (also on the CMD line); finally, one or more blocks data may be sent in one direction (on the data line(s)), each appended with a CRC.
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(1) When no data is being transmitted, data lines are held low. (2) Data block is preceded by a start bit (‘0’); an end bit (‘1’) follows the CRC. (3) The CRC is the 16-bit CCITT CRC. (4) During the busy signaling following a write, DAT0 only is held low. (5) See Figure - SD/MMC command and response formats for description of the command format. (6) See Figure - SD/MMC command and response formats for description of the command format. |
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(1) Command index is not valid for response formats R2 and R3. (2) CRC is not valid for response format R3. |
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