Product manual

Spinpoint M9TU-USB 3.0 Product Manual REV 1.0
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USB INTERFACE AND USB COMMANDS
6.3.5.2 Bulk Transaction
Bulk transfers can be used for large bursty data. Such examples could include a print-job sent to a printer or an
image generated from a scanner. Bulk transfers provide error correction in the form of a CRC16 field on the data
payload and error detection/re-transmission mechanisms ensuring data is transmitted and received without error.
Bulk transfers will use spare un-allocated bandwidth on the bus after all other transactions have been allocated.
If the bus is busy with isochronous and/or interrupt then bulk data may slowly trickle over the bus. As a result
Bulk transfers should only be used for time insensitive communication
as there is no guarantee of latency.
Bulk Transfers
• Used to transfer large bursty data.
• Error detection via CRC, with guarantee of delivery.
• Stream Pipe - Unidirectional
• Full & high speed modes only.
Bulk transfers are only supported by full and high speed devices. For full speed endpoints, the maximum bulk
packet size is either 8, 16, 32 or 64 bytes long. For high speed endpoints, the maximum packet size can be up to
512 bytes long. If the data payload falls short of the maximum packet size, it doesn't need to be padded with
zeros. A bulk transfer is considered complete when it has transferred the exact amount of data requested,
transferred a packet less than the maximum endpoint size of transferred a zero-length packet. Figure 6-27 shows
Bulk Transaction concept.
Figure 6-27: Bulk Transaction Model