Cisco CCNP Certifications Exam 642-845

Device classes codes 642-587 are decided upon by the Device Working Group of the USB Implementers Forum. If the class applies is to the entire device, the class code is assigned to the bDeviceClass field of the device descriptor, and if it is to be set for a single interface on a device, it is assigned to the bInterfaceClass field of the interface descriptor. It is also possible that multiple interfaces of the device are grouped by using 642-812 Interface Association Descriptor, in which case the class code is assigned to bFunctionClass fields of the descriptor. Class code is a single , so a maximum of 254 different device classes are possible (values 0x00 and 0xFF are reserved). If bDeviceClass is set to 0x00, the operating system will look at bFunctionClass of Interface Association Descriptors and bInterfaceClass of each interface to determine the 642-845 device class. Each class also optionally supports a SubClass and Protocol subdefinition. These can be used as the main device classes are continuously revised.