Abstract: A deterministic network protocol for connecting critical sensors, actuators and computing elements on a bi-directional, time-multiplexed, fiber optic or other media data bus, such that critical messages have concisely bounded latency and non-critical messages may be sent without impacting critical messages. It is a unique combination of a time-slot allocation protocol and a contention-based protocol in which global synchronization information is passed on the data media via a synchronization beacon.

Abstract: An intelligent multistation access unit is provided having a transmission speed detection circuit for determining the data transmission speed of an attached device attempting to gain access to a node of a multiple transmission rate digital data communications network. The intelligent multistation access unit is comprised of a speed detect circuit, which indicates the data transmission speed of the attached device, a switching circuit which directs the attached device to the speed detect circuit until switched to allow the attached device access to the network node, and a processor that controls the switching circuit and which permits the attached device access to the node depending on the data transmission speed indication.

Abstract: An expandable local area hub network is provided by the present invention. The network comprises a plurality of hubs connected along a common memory bus. Each hub includes a plurality of ports for interfacing with remote stations. An arbiter is coupled to the hubs for granting a hub controlling access to the memory bus to transmit a packet on the memory bus. In use, the arbiter receives requests from the hubs and designates a hub, based upon an internal protocol, temporary bus master hub by granting the temporary bus master hub controlling access to the memory bus.

Abstract: A system and method for communication and management of an aggregate is provided including a plurality of separate entities, each entity residing in a separate environment. The system includes a data path which is provided as a common medium. Each of the entities is connected to the data path for exciting the medium with a signal. All entities connected to the common medium receive the signal. A mapping path is also provided. The mapping path is implemented as a multitude of point-to-point connections such that each entity is connected directly to another entity via a point-to-point connection or connected to a first entity by a point-to-point connection and connected to a second entity by a point-to-point connection. The connections provide a known topology, allowing identification of all entities adjacent to a given entity to establish mapped adjacent entities. From these mapped adjacent entities all entities adjacent to the mapped adjacent entities are mapped until all entities of the aggregate are mapped.

Abstract: A system and method for passively measuring and correcting ring latency on a token or FDDI ring includes generating bits and token frames in a defined pattern according to the token ring protocol. A passive device coupled to the token ring measures CMIN, the minimum spacing, CMAX, the maximum spacing in bits and calculates Fi the frequency of changes in Cmin and Cmax between successive tokens or a token and a frame on the ring. A latency event vector Li is generated by the passive device. A controller responsive to the latency vector Li corrects the spacing between successive tokens or a token and frame to achieve a constant ring latency regardless of electrical or operational changes on the token ring.

Abstract: A looped bus system includes several nodes connected by unidirectional buses having opposite directions of signal transmission. The head of bus function for each bus is located at a node different from the head of bus function for the other bus. The head of bus function for each bus is located at the same node as the termination of bus function for the other bus. As a result, the buses can be reconfigured and nodes can be added freely by the use of a bus portion that is unused in the looped bus under normal condition.

Abstract: A token ring network performs address to port mapping by taking advantage of the abilities of the port switched modules and the neighbor notification process, in order to perform address to port mapping on each individual module. Ring monitors are switched from an upstream side of a port to a downstream side of a port when the neighbor notification process enters the port domain. The processor on the module records all the addresses received on the downstream side of the port, when the neighbor notification process is in the domain of that port. If it appears that the neighbor notification process is in the domain of two adjacent ports, the present invention only records addresses from the most downstream of the two adjacent ports, since such a situation is an indication that the upstream ports do not conform to MAC protocol.

Abstract: A communication network is comprised of several stations that constitute a logical ring to transmit and receive information. The logical ring is established and maintained by a token passing process and a solicit process. The token represents the right to transmit information between the stations in the logical ring. The solicit process solicits stations that are not in the logical ring. The stations in the network include at least one particular station. Each of the stations as well as the particular station include soliciting capability for carrying out the solicit process when holding a token. In addition, each station except for the particular station also includes first solicit repeat capability for repeating the solicit process at most a predetermined number of times when no frame arrives from other stations in the network, and the function of moving to an idle state when no frames arrives from other stations after the solicit process is repeated.

Abstract: A token ring interconnects a plurality of telephone stations and a ring server station. All communication is conducted via a TDM frame which includes a START field, a TOKEN field which can have any one of three states (free, busy or dedicated to communication by the ring server station), calling and called station address fields, a field for data to be sent to the ring server station and a plurality of data slots via which the telephone stations exchange data once the slots are allocated. When a connection is desired by a station it seizes a free token by making it busy, inserts pertinent field data and send the TDM frame on to the ring server station which establishes the connection via an answer frame.