AccessRunner ADSL-USB Modem Device Set Data Sheet
Table 4-1. Device Descriptors
Size of this descriptor in bytes.
DEVICE Descriptor Type.
USB Specification Release Number in Binary-Coded Decimal (i.e.,
2.10 is 0x210). This field identifies the release of the USB
Specification that the device and its descriptors are compliant with.
Class code (assigned by USB).
If this field is reset to 0, each interface within a configuration
specifies its own class information and the various interfaces
If this field is set to a value between 1 and 0xFE, the device
supports different class specifications on different interfaces and the
interfaces may not operate independently. This value identifies the
class definition used for the aggregate interfaces. (For example, a
CD-ROM device with audio and digital data interfaces that require
transport control to eject CDs or start them spinning.)
If this field is set to 0xFF, the device class is vendor specific.
Subclass code (assigned by USB).
These codes are qualified by the value of the bDeviceClass field.
If the bDeviceClass field is reset to 0, this field must also be reset to
If the bDeviceClass field is not set to 0xFF, all values are reserved
for assignment by USB.
Protocol code (assigned by USB). These codes are qualified by the
value of the bDeviceClass and the bDeviceSubClass fields. If a
device supports class-specific protocols on a device basis as
opposed to an interface basis, this code identifies the protocols that
the device uses as defined by the specification of the device class.
If this field is reset to 0, the device does not use class specific
protocols on a device basis. However, it may use class specific
protocols on an interface basis.
If this field is set to 0xFF, the device uses a vendor specific protocol
on a device basis.
Maximum packet size for endpoint zero (only 8, 16, 32, or 64 are
Vendor ID (assigned by USB).
Product ID (assigned by the manufacturer).
Device release number in binary-coded decimal.
Index of string descriptor describing manufacturer.
Index of string descriptor describing product.
Index of string descriptor describing the device’s serial number.
Number of possible configurations.