Abstract: A data communication analysis and simulation tool capable of simulating in real time the transmissions and data responses of at least one line replaceable unit communicating on at least one communication bus with at least one line replaceable unit under test, comprising a computer operating under a real time operating system and having available memory and means for accepting user input, and a programmed simulator resident in said computer comprising a plurality of processes to effectuate the simulation of the transmissions and data responses of at least one line replaceable unit. The programmed simulator allocates a portion of the available memory as a shared memory segment serving as a central database and supporting inter-process communication. The programmed simulator further generates graphical and textural images in response to communicated data from the line replaceable unit under test and user input to a monitor coupled to the computer.