When using a debugger in a real-time application on a target microprocessor equipped with IEEE ISTO-5001Nexus, a properly designed interface between the microprocessor and the debugger tool can result in a development system that has the capability approaching that of a logic state analyzer. Designers of Automotive Electronic Control Units (ECUs) have been using single chip microcontrollers in their designs for many years, but debug them in a special development system that is configured to run the microcontroller in an expanded mode. As microcontrollers become bigger and faster, a reliable method must be found to debug the software in these complicated devices while they are still in their single chip configuration. Creating a reliable debug environment involves more than just the selection of a suitable debugger tool. The designer of the target must also provide reliable, high frequency connections for the debug signals, and provisions for the debugger to interact not only the microcontroller, but also with the target power supply, Computer Operating Properly (COP) and Reset circuits.