This value is also used in Interface Descriptors to indicate a null class code triple. This base class is defined to be used in Device Descriptors to indicate that class information should be determined from the Interface Descriptors in the device. There is one class code definition in this base class. Use class information in the Interface Descriptors The table below shows the currently defined set of Base Class values, what the generic usage is, and where that Base Class can be used (either Device or Interface Descriptors or both). Some defined class codes are allowed to be used only in a Device Descriptor, others can be used in both Device and Interface Descriptors, and some can only be used in Interface Descriptors. One place is in the Device Descriptor, and the other is in Interface Descriptors. There are two places on a device where class code information can be placed. That terminology is not used in the USB Specification). (Note that ‘Base Class’ is used in this description to identify the first byte of the Class Code triple. The information is contained in three bytes with the names Base Class, SubClass, and Protocol. USB defines class code information that is used to identify a device’s functionality and to nominally load a device driver based on that functionality.
0 Comments
Leave a Reply. |