Hi, I am trying to debug my application using uVision2 and the Monitor 51 debugger. I am using the USBSimm development board and the mon-ext-sio0-co.hex file that comes with the Cypress development kit. I am able to download the code onto the chip using the monitor. The code also runs fine so long as there are no breakpoints in the code. The chip re-enumrates and Windows detects the new device fine. However, as soon as I put in some breakpoints, the Windows Device Manager shows erros for the device. Moreover, if I disable the "Stop Program Execution with Serial Interrupt" so that I can share serial port 0 with the monitor, that also messes up everything. If anybody has had similar problems or know what's going on, I would be very grateful. Thanks, Hersh