On a bus-based shared memory multiprocessing system, the system bus monitoring and analysis are crucial for system integration test and performance analysis. In this paper, the design and implementation of a bus monitoring instrument for the TICOM-III system are decribed. The instrument dedicated to TICOM-III, which is called the Bus Information Procssing Unit, analyzes the bus state and measures the bus utilization. It performs many useful functions to help debugging the system, and offers a simple user interface.