SanDisk SD Card

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Revision 2.2Chapter 4 – SD Card Protocol DescriptionSanDisk SD Card Product ManualFigure 4-2Multiple Block Read OperationFrom hostto card(s)From cardto hostData fromcard tohost"Stop" command stopsdata transferCMDCommandResponseCommandResponseDATData block CRC Data block CRCData blockCRCBlock read operationMultiple block read operationData stop operationThe block-write operation uses a simple busy signaling of the write operation duration onthe DAT0 data line (see Figure 4-3) regardless of the number of data lines used fortransferring the data.Figure 4-3Multiple Block Write OperationFrom hostto card(s)From cardto hostData fromcard tohostCRC OKresponseand busyfrom card"Stop" command stopsdata transferCMDCommandResponseCommandResponseDATData block CRC BusyData block CRC BusyBlock write operationData stop operationMultiple Block Write OperationCommand tokens have the coding scheme shown in Figure 4-4.Figure 4-4Command Token Format"Transmitter" bit:1=host command"Start" bitalways 0Command content: command andaddress information or parameter,protected by 7-bit CRC checksum"End" bitalways 10 1 Content CRC 1Total length = 48 bits© 2004 SanDisk Corporation 4-2 12/08/04
Revision 2.2Chapter 4 – SD Card Protocol DescriptionSanDisk SD Card Product ManualEach command token is preceded by a start bit (0) and succeeded by an end bit (1). Thetotal length is 48 bits. CRC bits protect each token to detect transmission errors; theoperation may be repeated.Response tokens have four coding schemes depending on their content. The token length iseither 48 or 136 bits. The CRC protection algorithm for block data is a 16-bit CCITTpolynomial. All used CRC types are described in Section 4.6Figure 4-5"Transmitter" bit:1=card response"Start" bitalways 0Response Token FormatResponse-content mirrored command andstatus information (R1 response). OCR Register(R3 response) or RCA (R6) protected by 7-bitCRC checksum"End" bitalways 1R1, R3, R60 0 Content1Total length = 48 bits"End" bitalways 1R20 0 Content= CID or CSD CRC 1Total length = 136 bitsIn the CMD line, the MSB bit is transmitted first, whereas the LSB bit is transmitted last.When the wide-bus option is used, the data is transferred four bits at a time (see Figure 4-6). Start and end bits, as well as the CRC bits, are transmitted for every one of the DATlines. CRC bits are calculated and checked for every DAT line individually. The card sendsthe host the CRC status response and busy indication on DAT0 only. (DAT1-DAT3 duringthat period is “don’t care”).Figure 4-6Data Packet Format"Start" bitalways 0MSB (4095)LSB (0)"End" bitalways 1Standard busy(only DAT0 used)0CRC 1MSNBlock lengthLSN"End" bitalways 1DAT3 0 4095 3 CRC 1Widebus (allfour datalinesused)DAT2 0 4094 2 CRC 1DAT1 0 4093 1 CRC 1DAT0 0 4092 0 CRC 1Block length /4© 2004 SanDisk Corporation 4-3 12/08/04
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Host Design Considerations:Applicat
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