SanDisk SDSDH-1024 Product Manual - Page 45

SD Card Protocol Description

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Revision 2.2 Chapter 4 - SD Card Protocol Description SanDisk SD Card Product Manual 4 SD Card Protocol Description 4.1 SD Bus Protocol Communication over the SD bus is based on command and data bit streams, which are initiated by a start bit and terminated, by a stop bit: • Command-token that starts an operation. A command is sent from the host either to a single card (addressed command) or to all connected cards (broadcast command). A command is transferred serially on the CMD line. • Response-token that is sent from an addressed card, or (synchronously) from all connected cards, to the host as an answer to a previously received command. A response is transferred serially on the CMD line. • Data-Data can be transferred from the card to the host or vice versa. Data is transferred via the data lines. Figure 4-1 "No Response" and "No Data" Operations From host to card(s) From host to card From card to host CMD DAT Command Operation (no response) Command Response Operation (no data) Card addressing is implemented using a session address that is assigned to the card during the initialization phase. The basic transaction on the SD bus is the command/response transaction (see Figure 4-1). This type of bus transaction transfers their information directly within the command or response structure. In addition, some operations have a data token. Data transfers to and from the SD Card are done in blocks. CRC bits always follow data blocks. Single and multiple block operations are defined. Note that the Multiple Block Operation mode is better for faster write operation. A multiple block transmission is terminated when a stop command follows on the CMD line. The host can configure a data transfer to use single or multiple data lines (provided the card supports this feature). © 2004 SanDisk Corporation 4-1 12/08/04

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Chapter 4 – SD Card Protocol Description
Revision 2.2
SanDisk SD Card Product Manual
© 2004 SanDisk Corporation
4-1
12/08/04
4
SD Card Protocol Description
4.1
SD Bus Protocol
Communication over the SD bus is based on command and data bit streams, which are
initiated by a start bit and terminated, by a stop bit:
•
Command
—token that starts an operation. A command is sent from the host either to a
single card (addressed command) or to all connected cards (broadcast command). A
command is transferred serially on the CMD line.
•
Response
—token that is sent from an addressed card, or (synchronously) from all
connected cards, to the host as an answer to a previously received command. A
response is transferred serially on the CMD line.
•
Data
—Data can be transferred from the card to the host or vice versa. Data is
transferred via the data lines.
Figure 4-1
“No Response” and “No Data” Operations
Card addressing is implemented using a session address that is assigned to the card during
the initialization phase. The basic transaction on the SD bus is the command/response
transaction (see Figure 4-1). This type of bus transaction transfers their information directly
within the command or response structure. In addition, some operations have a data token.
Data transfers to and from the SD Card are done in blocks. CRC bits always follow data
blocks. Single and multiple block operations are defined. Note that the Multiple Block
Operation mode is better for faster write operation. A multiple block transmission is
terminated when a stop command follows on the CMD line. The host can configure a data
transfer to use single or multiple data lines (provided the card supports this feature).
Command
CMD
From host
to card(s)
DAT
From card
to host
Response
Command
Operation (no response)
Operation (no data)
From host
to card