SH7216 Datasheet, PDF (6/32 Pages) Renesas Technology Corp – USB Mass Storage Class

SH7216 Group
USB Function Module: USB Mass Storage Class
3.3 Bulk-Only Transport
With Bulk-Only Transport, data is transferred between the host PC and a function using bulk data transport only.
Bulk transport can be divided into two types, depending on the direction in which the data is sent. If data is sent from
the host controller to the function, bulk-out transport is used. If data is being sent to the host controller from the function,
bulk-in transport is used.
With Bulk-Only Transport, a combination of bulk-out transport and bulk-in transport determined in advance is used to
transfer data between the host and the function. Bulk-Only Transport always uses the combination of bulk transports
shown in figure 2. These bulk transports have different meanings, but they are handled as stages (transports).
Command transport (CBW)
Start
Bulk-out transoprt
Data transport
Bulk-out transoprt
Bulk-in transoprt
Status transport (CSW)
Bulk-in transoprt
End
Figure 2 Relationship between Transfer Methods and Transports
In order to tell the host PC that the Bulk-Only Transport protocol is being used, a value of H'50 must be entered in the
bInterface Protocol field of the Interface Descriptor.
3.3.1 Command Transport
In command transport, commands are sent from the host PC to the function using bulk-out transport. This command
packet is defined as the Command Block Wrapper (CBW), and Bulk-Only Transport must always begin with the CBW.
The CBW is sent from the host PC as a 31-byte packet, using bulk-out transport.
It is sent using the format shown in table 3.
Table 3 Command Transport Formats
7
6
5
4
3
2
1
0
H'00-H'03
dCBWSignature
H'04-H'07
dCBWTag
H'08-H'0B
dCBWDataTransferLength
H'0C
bmCBWFlags
H'0D
Reserved (0)
bCBWLUN
H'0E
Reserved (0)
bCBWCBLength
H'0F-H'1E
CBWCB
REJ06B0897-0100/Rev.1.00
July 2009
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