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The purpose of this application note is to demonstrate the implementation of theUniversal Serial Bus device configuration process, using the C541U microcontroller.This configuration process is called bus enumeration. The C541U has an Intel 8051compatible core, which is integrated with a USB Device Core (UDC) and a MemoryManagement Unit (MMU).List of Figures31 Introduction…42 USB Background…...52.1 Hub and Device Topology….52.2 Device Configuration Process63 HID (Human Interface Devices) Background... 74 Hardware Architecture of C541U…..84.1 Fundamental Structure……...84.2 USB Module..95 Software Architecture of C541U…...105.1 Software Initialization Routine………..105.2 Software Interrupt Routines...105.3 Software Main Routine……..126 Operating Environment…..136.1 Keil C51 Compiler.136.2 C541U Starter Kit..136.3 CATC Bus Inspector………..146.4 OHCI/UHCI Host..147 Conclusion….15Appendix A Software Flowchart16Appendix B References…..23Appendix C Software Files 24Appendix D Key Button Implementation...25Figure 1 – USB TopologyFigure 2 – USB HID Descriptor StructureFigure 3 – Block Diagram of the C541UFigure 4 – Block Diagram of the USB ModuleFigure 5 – 3-Stage Control TransferFigure 6 – Overview of Development Setup
