The purpose of this application note is to demonstrate the implementation of the
Universal Serial Bus device configuration process, using the C541U microcontroller.
This configuration process is called bus enumeration. The C541U has an Intel 8051
compatible core, which is integrated with a USB Device Core (UDC) and a Memory
Management Unit (MMU).
List of Figures3
1 Introduction…4
2 USB Background…...5
2.1 Hub and Device Topology….5
2.2 Device Configuration Process6
3 HID (Human Interface Devices) Background... 7
4 Hardware Architecture of C541U…..8
4.1 Fundamental Structure……...8
4.2 USB Module..9
5 Software Architecture of C541U…...10
5.1 Software Initialization Routine………..10
5.2 Software Interrupt Routines...10
5.3 Software Main Routine……..12
6 Operating Environment…..13
6.1 Keil C51 Compiler.13
6.2 C541U Starter Kit..13
6.3 CATC Bus Inspector………..14
6.4 OHCI/UHCI Host..14
7 Conclusion….15
Appendix A Software Flowchart16
Appendix B References…..23
Appendix C Software Files 24
Appendix D Key Button Implementation...25
Figure 1 – USB Topology
Figure 2 – USB HID Descriptor Structure
Figure 3 – Block Diagram of the C541U
Figure 4 – Block Diagram of the USB Module
Figure 5 – 3-Stage Control Transfer
Figure 6 – Overview of Development Setup