Host/Device Packet Transfer Order; Command Queuing; Bi-Directional Command Protocol; Standard Descriptors - Seagate M8U-Internal SpinPoint Product Manual

6.4.1.3

Host/Device Packet Transfer Order

The host shall send the CBW before the associated Data-Out, and the device shall send Data-In after the
associated CBW and before the associated CSW. The host may request Data-In or CSW before sending the
associated CBW.
If the dCBWDataTransferLength is zero, the device and the host shall transfer no data between the CBW and
the associated CSW.
6.4.1.4

Command Queuing

The host shall not transfer a CBW to the device until the host has received the CSW for any outstanding
CBW.
If the host issues two consecutive CBWs without an intervening CSW or reset, the device response to the
second CBW is indeterminate.
6.4.1.5

Bi-Directional Command Protocol

This specification does not provide for bi-directional data transfer in a single command.

6.4.2 Standard Descriptors

The device shall support the following standard USB descriptors:
• Device. Each USB device has one device descriptor (per USB Specification).
• Configuration. Each USB device has one default configuration descriptor, which supports at least one
interface.
• Interface. The device shall support at least one interface, known herein as the Bulk-Only Data Interface.
Some devices may support additional interfaces, to provide other capabilities.
• Endpoint. The device shall support the following endpoints, in addition to the default pipe that is required
of all USB devices:
(a) Bulk-In endpoint
(b) Bulk-Out endpoint
Some devices may support additional endpoints, to provide other capabilities. The host shall use the
first reported Bulk-In and Bulk-Out endpoints for the selected interface.
• String. The device shall supply a unique serial number.
The rest of this section describes the standard USB device, configuration, interface, endpoint, and string
descriptors for the device.
6.4.2.1

Device Descriptor

Each USB device has one device descriptor (per USB Specification). The device shall specify the device class
and subclass codes in the interface descriptor, and not in the device descriptor. (Table 6-20)
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