Multiplex communications – Communication techniques for information carried in plural... – Address transmitted
Patent
1997-05-08
1999-05-25
Hofsass, Jeffery A.
Multiplex communications
Communication techniques for information carried in plural...
Address transmitted
370442, 370443, 370459, H04J 324
Patent
active
059075570
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an industrial or domestic-type local network, for controlling and/or monitoring several appliances by means of one or several distributed (or delocalized) computers.
The I2C bus is an example of such a network. The I2C bus is inexpensive but its length is limited to a few meters and only enables to control a limited number of appliances. Moreover, the information rate on this bus is particularly low (100 kbits/s), which limits its use to transferring simple commands, of the on/off type, or digital variables which change slowly. Transferring commands takes-up a non-negligible part of the processing power of the computer which manages the network.
FIG. 1 shows an example of FIP network, which is a more efficient network than the I2C bus. This network includes a set of circuits, or nodes, M and N1 to N3 connected to a common bus. Circuit M is a master circuit which manages the information exchanges between nodes N1 to N3. The exchanges are performed by means of a so-called "subscriber" mechanism. Each node N includes at least one consumer subscriber (receiver) R and at least one generator subscriber (transmitter) T. Each generator subscriber has a single address. Each consumer subscriber is mat to receive the information transmitted by a single generator subscriber which is associated by the user with the consumer subscriber by a programming of the nodes.
In the example of FIG. 1, nodes N1 to N3 include generator subscribers T with respective addresses 1 to 3. The consumer subscribers of nodes N1 to N3 are respectively associated with the generator subscribers having as respective addresses 2, 1 and 2. Thus, one-way or two-way logic links, shown in dotted lines, are established between the various network nodes.
The generator subscribers T are successively questioned by master circuit M, the questioning consisting, for example, in the transmission by the master circuit of the addresses of these generator subscribers. For each questioning, the corresponding generator subscriber recognizes its address and transmits its content, while the associated consumer subscribers also recognize the address and prepare to receive this content.
A FIP network is particularly reliable in that a consumer subscriber only receives information from the associated generator subscriber and thus cannot receive spurious commands from a node connected by mistake or malevolence to the network
However, a disadvantage of a FIP network is that it becomes inoperable when the bus is accidentally broken.
FIG. 2 illustrates a so-called "flooding" technique enabling a network to operate even if connections between nodes are broken. Nodes N1 to N5 of this network are interconnected by point-to-point links. Each node is likely to be connected to several other nodes by point-to-point links, not all possibilities being necessarily used. Thus, for example, node N3 is connected to nodes N1, N2, N4, and N5; node N1 being also connected to node N4. Each node is provided to repeat on each of its point-to-point links an information that it receives for the first time on one of its links, which is shown by an arrow from node N1 towards node N3 and by four arrows originating from node N3. It is thus ensured that each node of the network receives each information at least once. A node can even receive the same information several times. Thus, node N1 transmits an information which simultaneously arrives onto nodes M3 and N4. Little after, node N3 repeats this information which is again received by node N4. The nodes in the network are thus provided to take an information into account (to repeat it and, in case of need, process it) only upon its first arrival.
Thus, each node can receive a same information several times through different paths. If one of the paths is accidentally broken, the node receives the information through the remaining paths. For example, if the link between nodes N1 and N4 is broken, node N4 still receives the information from node N1 via node N3.
In the control and monitoring of appliances or of an
REFERENCES:
Control Engineering, Sep. 1991, pp. 65-67, J.P. thomasse, P. Lorenz, J.P. Bardinet, P. Leterrer, T. Valentin. `Factory Instrumentation Protocol: Model, Products, and tools.`.
Hofsass Jeffery A.
Plevy, Esq. Arthur L.
Townsend Clement
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