SDCMD_DESCRIPTOR structure (sddef.h)
The SDCMD_DESCRIPTOR structure defines a Secure Digital (SD) card command.
Syntax
typedef struct _SDCMD_DESCRIPTOR {
SD_COMMAND_CODE Cmd;
SD_COMMAND_CLASS CmdClass;
SD_TRANSFER_DIRECTION TransferDirection;
SD_TRANSFER_TYPE TransferType;
SD_RESPONSE_TYPE ResponseType;
} SDCMD_DESCRIPTOR, *PSDCMD_DESCRIPTOR;
Members
Cmd
Contains a value of type SD_COMMAND_CODE that specifies the SD command. Cmd can be one of the following values.
| Value | Meaning |
|---|---|
| SDCMD_IO_RW_DIRECT | Indicates a read or write operation of a single byte. |
| SDCMD_IO_RW_EXTENDED | Indicates a read or write operation on a buffer in memory. |
CmdClass
Contains an enumeration value of type SD_COMMAND_CLASS that specifies the class of the SD command.
TransferDirection
Contains an enumeration value of type SD_TRANSFER_DIRECTION that indicates the direction of the data transfer.
TransferType
Contains an enumeration value of type SD_TRANSFER_TYPE that indicates the type of the data transfer.
ResponseType
Contains an enumeration value of type SD_RESPONSE_TYPE that indicates the type of response that the card sends in response to the command indicated in the Cmd member.
Remarks
To send a command to an SD device, a device driver must complete the following steps:
Set the RequestFunction member of SDBUS_REQUEST_PACKET to an SD_REQUEST_FUNCTION enumeration value of SDRF_DEVICE_COMMAND.
Initialize the CmdDesc member of SDBUS_REQUEST_PACKET to define the command.
Send the request to the bus driver by passing the initialized SDBUS_REQUEST_PACKET structure to either SdBusSubmitRequest or SdBusSubmitRequestAsync.
If a driver submits a command request without properly initializing the TransferDirection, TransferType, and ResponseType members of the command descriptor, the request will fail. These members cannot be 0.
Requirements
| Requirement | Value |
|---|---|
| Header | sddef.h (include Sddef.h) |