SH7216 Datasheet, PDF (8/32 Pages) Renesas Technology Corp – USB Mass Storage Class

SH7216 Group
USB Function Module: USB Mass Storage Class
3.3.3 Data Transport
Data transport is used to transfer data between the host PC and the function. For example, with the Read/Write
command, the actual data of the various storage sectors is sent using data transport.
Data transport is configured of multiple bus transactions.
Data transfers carried out using data transport use either bulk-out or bulk-in transport. The bmCBWFlags field of the
CBW data determines which type of transport is used.
(1) Data transport (bulk-out transport)
This section explains how data is transferred when bulk-out data transport is used.
This status is set if bit 7 of the bmCBWFlags field of the CBW data is 0, and the dCBWDataTransferLength field of
the CBW data is not 0.
Here, the function receives the anticipated length of the data indicated by the dCBWDataTransferLength field of the
CBW data. The data transferred at this point is needed when the SCSI command specified by the CBWCB field of
the CBW data is executed.
(2) Data transport (bulk-in transport)
This section explains how data is transferred when bulk-in data transport is used.
This status is set if bit 7 of the bmCBWFlags field of the CBW data is 1, and the dCBWDataTransferLength field of
the CBW data is not 0.
Here, the anticipated length of the data indicated by the dCBWDataTransferLength field of the CBW data is sent to
the host PC. The data transferred at this point is the result produced when the SCSI command specified by the
CBWCB field of the CBW data was executed.
3.4 Class Commands
Class commands are commands that are defined by the various USB classes. They use control transfer.
When USB Mass Storage Class Bulk-Only Transport is used as the data transport protocol, there are two types of
commands that must be supported. The class commands are indicated in table 5.
Table 5 Class Commands
bRequest Field Value
255 (H'FF)
254 (H'FE)
Command
Bulk-Only Mass Storage Reset
Get Max LUN
Meaning of Command
Resets the interface
Checks the number of LUNs supported
When the Bulk-Only Mass Storage Reset command is received, the function resets all of the interfaces used in USB
Mass Storage Class Bulk-Only Transport.
When the Get Max LUN command is received, the function returns the largest logical unit number that can be used. In
the sample system used here, there is one logic unit, so a value of 0 will be returned to the host.
REJ06B0897-0100/Rev.1.00
July 2009
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