Different schedules proposals for successive transmission for the general purpose network controller

General Purpose Controller Network Architecture is an experimental network architecture designed for interconnecting nodes in distributed embedded applications. It is provides deterministic access to the network medium to support distributed hard real-time application components. General Purpose Controller Network Architecture uses a token bus to transfer fixed sized frames. Token monitor issues an explicit token that contains the schedule using which the nodes are allotted medium access. The 37 byte frame structure includes a 5 byte header and a 32 byte payload. Payload within the token carries single byte addresses of the nodes on the network sorted in the order they are granted access to the medium. Only the node in possession of the token is granted medium access, and this node subsequently transmits the token to the node scheduled next in the token payload. Thus, the original General Purpose Controller Network Architecture allows only up to 32 nodes to be present on the network. This paper suggests three optimizations to the original General Purpose Controller Network Architecture concept. Primarily, the use of virtual tokens reduces the token overhead. Nodes can dynamically request bandwidth allocation to transmit periodic or sporadic messages. Finally, categorization of nodes as talkers and listeners and use of different schedules for successive transmission cycles increases the number of nodes on the General Purpose Controller Network Architecture bus.