PURPOSE: To realize an efficient inter-processor communication by transmitting and receiving continuously plural messages in a multi-processor system.

CONSTITUTION: The unit is constituted by providing a means for fetching transmitting descriptors 1-4 in accordance with a transmission actuating instruction, and also, providing a buffer identifier for showing a fact that buffer data written in a certain transmitting/receiving buffer is data of a start, a middle or an end of a transmitting message, or a fact that the buffer data is single buffer data and forms the transmitting message, in its transmitting descriptors 1-4.