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Spinpoint M8U-Internal Product Manual REV 3.4
91
INSTALLATION
6.4.3.3 Data Transfer Conditions
This section describes how the host and device remain synchronized. The host indicates the expected transfer
in the CBW using the Direction bit and the dCBWDataTransferLength field. The device then determines the
actual direction and data transfer length. The device responds as defined in 6 - Host/Device Data Transfers by
transferring data, STALLing endpoints when specified, and returning the appropriate CSW.
6.4.3.3.1 Command Transport
The host shall send each CBW, which contains a command block, to the device via the Bulk-Out endpoint.
The CBW shall start on a packet boundary and end as a short packet with exactly 31 (1Fh) bytes transferred.
The device shall indicate a successful transport of a CBW by accepting (ACKing) the CBW. If the CBW is not
valid - CBW Not Valid. If the host detects a STALL of the Bulk-Out endpoint during command transport, the
host shall respond with a Reset Recovery.
6.4.3.3.2 Data Transport
All data transport shall begin on a packet boundary. The host shall attempt to transfer the exact number of
bytes to or from the device as specified by the dCBWDataTransferLength and the Direction bit. The device
shall respond as specified in 6 - Host/Device Data Transfers.
To report an error before data transport completes and to maximize data integrity, the device may terminate
the command by STALLing the endpoint in use (the Bulk-In endpoint during data in, the Bulk-Out endpoint
during data out).
6.4.3.3.3 Status Transport
The device shall send each CSW to the host via the Bulk-In endpoint. The CSW shall start on a packet
boundary and end as a short packet with exactly 13 (Dh) bytes transferred. Figure 6-36 - Status Transport
Flow defines the algorithm the host shall use for any CSW transfer.
The CSW indicates to the host the status of the execution of the command block from the corresponding
CBW.
The dCSWDataResidue field indicates how much of the data transferred is to be considered processed or
relevant. The host shall ignore any data received beyond that which is relevant.
6.4.3.3.4 Phase Error
The host shall perform a Reset Recovery when Phase Error status is returned in the CSW.
6.4.3.3.5 Reset Recovery
For Reset Recovery the host shall issue in the following order::
(a) a Bulk-Only Mass Storage Reset
(b) a Clear Feature HALT to the Bulk-In endpoint
(c) a Clear Feature HALT to the Bulk-Out endpoint
6.4.4 Host/Device Data Transfers
6.4.4.1 Overview
A Bulk-Only Protocol transaction begins with the host sending a CBW to the device and attempting to make
the appropriate data transfer (In, Out or none). The device receives the CBW, checks and interprets it,
attempts to satisfy the host's request, and returns status via a CSW. This section describes in more detail this
interaction between the host and the device during normal and abnormal Bulk-Only Protocol transactions.