A microcomputer communication network suitable for real-time applications is developed by using inexpensive, programmable data control chip. The communication network is characterized by open-ring structure, message train, and centralized control. Open-ring structure coming from D-Net, eliminates overhead due to message removal in conventional closed ring. At each token turn-around, message train is made by multiple accessing of attached nodes. Channel efficiency can be enhanced by multiple accessing. Centralized control makes protocol design simple. Access ordering is sequentialized with round robin by using explicit token. Channel access time is bounded with finite limit by this collision-free protocol. This boundness is shown in simulation result. This feature is very important for real-time application.