The problem I am having is about serial port. I loaded Keil Monitor file: mon-ext-si0-c0 into SIMM module through EZ-USB Control Panel. It appeared to load properly. Then I opened UVision to debug any EZ-USB example. I selected and opened ep_pair.c. Then through steps, I clcked on Project-Options for Target 'Target1'. And on the debug tab, settings are selected for 19200 baud and Com2. Then click START\STOP on Debug prompted a Windows Error Dialog that SERIAL INTERFACE is not in use or used by other program. The SIMM module is connected properly to serial port on the back of pc. I tried other com port settings, but the problem remained the same. I wonder if any of you have similar problems as mine.