Debugging aids for systems-on-a-chip

Serial debugging can overcome the problems which have arisen with monitor-based debugging and in-circuit emulation. Serial debug is a configuration of hardware and software which allows a host to communicate with an embedded chip. There are a number of different implementations of serial debug methodologies but all use a small number of pins to talk to the target CPU from a host computer. The most popular serial debugging methodology is Background Debug Mode (BDM) which is implemented on most Motorola microcontroller families. A microcode based monitor resides on each microcontroller and is interfaced to debugger software which runs on the host (usually a PC). The host will display the microcontroller's on-chip resources and status and will allow simple debugging operations to be performed, such as reading and writing to registers and memory locations.