TAILIEUCHUNG - USB Complete fourth- P14

USB Complete fourth- P14:This book focuses on Windows programming for PCs, but other computers and operating systems also have USB support, including Linux and Apple Computer’s Macintosh. Some real-time kernels also support USB. | Chapter 4 Table 4-7 The interface association descriptor can link multiple interfaces to a single function. Offset decimal Field Size bytes Description 0 bLength 1 Descriptor size in bytes 08h 1 bDescriptorType 1 The constant Interface Association 0Bh 2 bFirstInterface 1 Number identifying the first interface associated with the function 3 blnterfaceCount 1 The number of contiguous interfaces associated with the function 4 bFunctionClass 1 Class code 5 bFunctionSubClass 1 Subclass code 6 bFunctionProtocol 1 Protocol code 8 iFunction 1 Index of string descriptor for the function Most device classes specify the class at the interface level rather than at the device level. Assigning functions to interfaces enables a single configuration to support multiple functions. When two or more interfaces in a configuration are associated with the same function the interface association descriptor tells the host which interfaces are associated. For example a video-camera function may use one interface to control the camera and another to carry video data. The Interface Association Descriptor ECN says that the descriptor must be supported by future implementations of devices that use multiple interfaces to manage a single device function. Devices that comply with the video-class and audio specifications must use interface association descriptors. Class specifications that predate the IAD don t require it. For example the audio class specification defines a class-specific descriptor to associate audio interfaces in a function. Hosts that don t support the IAD ignore it. Windows began supporting the descriptor with Windows XP SP2. In USB devices every function with multiple interfaces must use an IAD. To enable hosts to identify devices that use the Interface Association descriptor the device descriptor should contain the following values bDeviceClass EFh miscellaneous device class bDeviceSubClass 02h common class bDeviceProtocol 01h interface association descriptor .

• Phần cứng
• sửa chữa máy tính
• sổ tay phần cứng
• MainBoard
• thiết bị máy tính
• thiết bị mạng
• lắp ráp máy tính
• Phần cứng máy tính
• lỗi máy tính
• hệ thống mạch máy tính
• điện máy tính
• Tài liệu máy tính