Hardware without software is of little use. Systems that ease the task of debugging software reduce cost and speed development. This paper presents guidelines for designing processors that ease debugging for real-time computer systems. Special hardware can aid the debugging process by tracing execution and accesses to memory. Such hardware requires access to signals that may not be readily available. Other, less exotic hardware provides an interface to the programmer and other processors. The hardware and software of the debugging system should not alter the real-time characteristics of the system under test and should be able to operate on a field-grade processor. It is undesirable to require special versions of processor hardware and software for the debugging system.