Local area network for distributing data communication, sensing and control signals

.' FIELD OF THE INVENTION-.' 7

The present invention relates to the field of wired communication and control networks, and, more particularly, to local area networks and networks used for sensing, communication, and control.

BACKGROUND OF THE INVENTION 7

Local area networks. (LANs) for distributing data communication, . . '.. ' ׳ . ־ .' ׳ J ׳:

sensing, and control signals are often based on a “bus” topology, as shown in Figure 1. Such a network 10 relies on shared electrically-conducting . communication media 1, usually constituted by a twisted-pair of electrical ¹ ״ ׳ - .^: . . ׳ . ׳I: .

conductors or a coaxial cable. Network data terminal equipment (DTE) units 5, : . 6, and 7 are connected via respective network adapters 2, 3, and 4 to communication media 1. Network adapters 2, 3, and 4 function as data

. 7 -: ' 7 'י .. / communication equipment (DCE) units, and are tapped into!; communication media 1, forming parallel electric connections, and thereby interface between

DTE units 5, 6, and 7 and communication media 1. Such network adapters are

' . '/! \ ' ,. - .. .'7.-' .:. ׳' : י.:

also commonly referred to as “NIC”, an example of whicn is the Network ־ ..'־ . ־ . ' . . ' . ’ . .. ' I;׳. .. .

interface Card TREE 802 (Ethernet). Such a topology is commonly used for ־.' ׳..׳ . . - ׳.. i^: r .

connecting personal computers (PCs) in a network. Network adapters can be stand-alone units, integrated into the DTE unit or housed therewith in a.

common enclosure. ./7/.

. '.־ i. ‘•7 7 . . ׳ \ : - .' .־; ./: - /. . \ ' '7 ־' ί j. - .. .

' •7 7 ר' י '' ' . - G'/ ' ' . ίί ' 7 .. .-.7.-.

' '- .' 7 'י .י ' i '...'.. . .7/ .- Ir. . י . . /;. WO .®1/Φ5052 , . /.J. ;/..PCT/JL®iwe384’ ־ A.A Α..Α'-y/A? - ^?A A.; <A-2.?.;Aי (׳/Α.^'-..-^;Α.Υ

Control neivvor^s, ^^T^tconnectin^ .sensors,. actuators, and DTK’s also ; commonly use the same topology, such as the network described, in US Patent . ׳ No. 4,918,690 (Markkula, Jr. et al.) and shown, in Figure 2. In a network 20, network adapters 22, 23, and 24 function, as DCE’s, but are commonly referred.

. to as “nodes”. The payloads 25, 26, and 27 are composed of sensors^ actuators,’ and.DTE’s. ׳ ׳ < ׳ .' . Hereinafter, the term “node” . is used for . .'both control and data- ' communication apphcations.

A topology (such as bus topology) whose physical layer communication 10 media employs multi-point connections, is not optimal for communication, and . exhibits the following drawbacks: ^: .

1. The maximum length of the communication media is limited .

2. The maximum number of units connected to the bus is limited.

3. Complex transceivers are required in order to interface the commumcation media.

4. The data rate is limited. . \ . ’־ λ. :^;.

5. Terminators are required at the communication media ends_J thus . ' complicating the installation. )/

6. At any given time, only single connected unit may transmit; all . others'.are receiving.

7. In case of short circuit in the bus, the whole network fails. Localizing the fault is very difficult.

; Despite these drawbacks, however, bus topology offers two unique advantages:

1. If the application requires “broadcast” data distribution, where the data generated by a given node must be distributed to all (or a . majority of) the nodes in the network, network operation is very . efficient. This . is because only a single , network operation is .-/ required (i.e., to establish which node is the transmitter). The broadcast data is received by 511 0-¼ nodes in the network m parallel without additional network overhead.

2. The broadcast message is received simultaneously by all receiving nodes in the network. This is important in real-time control applications, for example, where orderly operation of the units must be maintained.

The communication-related drawbacks described above are solved by networks constructed of multiple communication links, wherein each instance of the link communication media connects only two units in the network. Here, 10 the physical layer in each segment is independent of other links, and employs a point-to-point connection. Data and/or messages are handled and routed using data-link layer control. One example of such system fof LAN purposes is the Token-Ring, described in the IEEE §02 standard. An example of a corresponding control network is described in US patent 5,095,417 to 15 Hagiwara et al. Both networks use circular topology (“ring topology”) as fflustrated in Figme 3. A network30 interconnects nodes (or NIC’s) 32, 33, and 34 by three separate cables 31A, 31B, and 31C, each connecting a pair of nodes and forming three distinct physical layer communication links. Payloads (or DTE’s)35,36, and 37 are respectively connected to the appropriate nodes.

Both the Hagiwara network and the Token-Ring network use unidirectional communication in each communication link and require a circular topology. The PSIC network described in US Patent 5,841,360 to the present inventor teaches a similar network where the use of a circular topology is optional, and bi-directional communication (either half-duplex or full-duplex mode) is employed in the communication links.

The above-mentioned prior art patents and networks are representative only. Certain applications are covered by more than one issued patent . Additional discussion concerning the above-mentioned topologies can be loimd in U.S. Patent 5,841,360 entitled “Distributed serial control system’ wmeh 30 issued November 24, 1998 and co-pending U.S patent 6,480,510 entitled :Local are;

— network of serial intelligent cells ,both in. the name of the present inventor. <

Networks such as those illustrated in Figure 3 and in WO 96/37984 typically use a “store and forward” mechanism, wherein the data received at a

-־־------. .

specific node is decoded at least to the data-link layer, and then re-encoded and transmitted to another point in the network as determined by the network control. This use of point-to-point communication links eliminates the communication drawbacks enumerated above in broadcast-based networks, but it lacks the two unique advantages of the broadcast technology, as also previously enumerated. Because the data is not inherently distributed throughout a network based solely on point-to-point communication links, such a network incurs a heavy overhead when broadcast is needed and exhibits delays in the propagation of messages. The overhead and delays result from the need to decode and re-encode messages at each node.

WO 96/37984 relates solely to the arbitration mode of a specific type of network (*daisy chain bus’), and describes a method and system for defermim'-ng- which node will be the transmitting node during the subsequent operational mode, with which WO 96/37984 is not itself concerned. WO 96/37984 does not address the operational phase, and therefore does not address the need to reduce delay broadcast capability during the subsequent operational mode when data is transmitted.

There is thus a widely-recognized need for, and it would be highly advantageous to have, a means of implementing a network which allows for both improved communication characteristics, while also supporting broadcast discipline and fast message distribution along the network.

SUMMARY OF THE INVENTION. '

It is an object of the present invention to provide a local area network in which at least some of the drawbacks described above axe reduced or eliminated.

^-09-2001^ 12:25

REINHOLD COHENS PARTNERS

,, [עט. 671מ0

IL0000384

“־⁵־ י .

To this end, the present invention provides a local area network based on nodes connected to payloads. The nodes are interconnected to fonn a network of half-duplex or full-duplex communication links based on electrically conducting communication media such as twisted conductor pairs or coaxial 5 cables. Each communication linlc interconnects two nodes in the network. Each node is capable of being dynamically configured as a transmitter or as a receiver. In addition, however, each receiving node can also be dynamically configured to be a repeater, which simply retransmits the received data. In this way, data from one link can be repeated to all other links via an automatic 10 multicast process. In normal operation, a specific node is selected as the data generating unit to transmit data to the network. All other nodes serve as repeaters and receivers, and hence the data is multicast instantaneously from the selected data generating node throughout the nelwork. After completing this transmitting session, another node may be selected as the data generating node, 15 with all other nodes serving as repeaters and receivers in a like fashion.

A network according to the present invention can also be configured in a circular topology, enabling operation to continue even when there is a malfimction or loss of a communication link.

Therefore, according to the present invention there is provided a local 20 area network for distributing data communication, sensing, and control signals, the local area network including at least three nodes having an operational mode and being interconnected by at least two distinct physical layer communication links according to a topology wherein:

each of said conunumcation links has two electrical conductors 25 for allowing serial bit streaming communication in half-duplex mode, each of said communication links connects two of said nodes in a point-to-point configuration whereby the data stream flows from an output configured port of a node to an input configured port of the connected node, at least one of said nodes is connected to a payload, and

AMENDED SHEET

C M rt 4 5 Λ 7 f » rt ». t ’» V. r« tv 1 . * » t

05-09-2001 ^{101 12:25}. REINHOLD COHEN& PARTNERS .־ 671מס ^U11[_0000384 aat least two of said nodes have said operational mode selectable as a data-generating operational mode, wherein all ports are configured ‘ as output ports;

characterized in that:

the topology may be any arbitrary topology, at least one of said nodes has said operational mode selectable as a repeating operational mode wherein the serial bit stream is directly and transparently switched in the phyacal layer from an input configured port to all output configured ports; and the local area network has a state selectable from a group of at least two distinct states each characterized by having a single selected one of said nodes in the data-generating operational mode with a remainder of said nodes in operational mode selected from a group containing the receiving operational mode and the repeating operational mode.

AMENDED SHEET

'.'־'/'./.Λ / 6- > '. ל י-'.^'.? v>\ . BFIEF DESCRIPMON OF THE DRAWINGS . ' ל ׳׳

In order to understand the inventioB .and to see how it may be carried out'׳ ׳ ' in practice, some prefertodembodiments will now be described, by way of .

. non-limiting example only, with reference׳ to the accompanying drawings, in : 5 which: ל.';

Figure ! .shows a prior-art LAN for data communication, employing bus ל י./.־' topology. ׳. .ל י״ ל ' ’:לל י

Figure 2 shows a prior-art LAN for control, employing bus topology.

Figure 3 shows a prior-art network for control or data-comTrmmicsHrm^ employing circular topology. ל \

Figure 4 describes a general block diagram of a node according to the ל׳ present invention. (.,

Figures 5a, 5b, 5c,and 5d show different possible states of anode according to the present invention.

Figure 6 shows a state of a network according to the present invention.

Figure 7 shows a general block diagram of a node according to the ׳ invention, wherein power is also carried by the network.

Figure 8 shows a state of a network according to the present invention, wherein power is carried by the network and employing circular topology.

Figures 9a aud 9b show different possible states of a node in circular .

topology network according to the present invention.

Figure 10 shows a block diagram of a node according to a preferred .

embodiment. '.־

Figure 11 shows a block diagram of a node according to the present invention, supporting three line couplers.

Figure .12 describes various possible'node states, and the .respective . . required switches states for a node as shown in Figure 10. ׳ . WO01/®5®®2 ' ;.?'i .FCMLW/®®3§4 י .י י- _:; V 3 . _;. : -7- ־> ׳/ /CT.'.

Λ : :DESCRIFnON OF THE ?REFERRED EMBODIMENTS .:/ .. .- './ ' ׳ ׳

־.: The principles and operation of a network according to the present .^:/ mye11tioii1:'.inay' be :understood' with reference to the drawings/and^the accompanying description. The drawings and descriptions herein are 5 conceptual only. In actual practice, a single circuit can implement one or more functions; alternatively, each function can be implemented by a plurality of : components and circuits. In the drawings and descriptions, identical reference numerals indicate those components that are common to different embodiments or configurations. ־,''.,..'.''':'.י'

Figure 4 schematically shows a node 40 according to the present invention. Node 40 contains the following functional blocks: :

® A power supply 41, fed from a power source 52, which converts ; incoming power to the voltage, or voltages, required by the node and the node’scomponents.Inaddition, power supply 41 may also feed a 15 payload 49 connected to node :40. If used, this feeding function is carried out by a payload interface48. (For clarity, Figure 4 omits the individual connections distributing power from power supply 41 to the power_: L consuming blocks of node 40.) ® : A payload interface 48 which adapts node 40 to a specific payload 49.

. - Various payload types can be employed, such as sensors, actuators and data units, either analog or digital, functioning either as output dr as \ input For exar^ .: < ־:׳ ⁸ Analog sensor. The payload consists of analog sensor used to measure any physical phenomena. In most cases, the payload ׳'25 ׳.Λ- . ,־. interface contains an A/D converter.

/;׳ /. ,/־ ^B : Digital sensor. The payload is a switch, button, etc. . .

.׳;'׳..'::'.;.'ז a : . Analog actuator. To. most cases, the payload contains a D/A converter controlling the parameters of the analog actuator.

.?;..; ' .WO®1/®S®92 . . 5 : / ־ .^: ־CT/HJWJO4 A

..

;;-> .: Data 'related unit. :In'.the:.case of digital/coimnimication/'the^/: '.:'.>

. payload consists of DTE and the payload interface contains a DTE .it^rface.-־ .; :.;T < a -. Non-digital-. data. Data .such .as .video,/ voice,: analog .5 '. /.;.- communication or any other of data type. If analog, data is input to . ׳ the node, the payload interface is:likely to.use an A/D converter. .׳.

The above examples are not intended to limit in any way the general payload definition. Furthermore, multiple devices of various types can be used. In some cases, payload 49 may use power from node 40. For example, the excitation voltage to analog

־.' Some nodes in the network may not be connected to a payload^ or may not have any payload interface at all. Nodes configured in this manner would be used as repeaters only, such as a node 9© in

Figure §. Repeater nodes can be used, for example, to extend the . distance between nodes beyond the regular limit ® . Line couplers 42 and 43, which interconnect node 40 with up to two other /;.:nodes,'; each';via communication media 50 and 51, respectively (also . . / referred to as . “lines”). Each communication media supports communication, between two nodes of the network. For clarity only, the two ports are' designated ‘Left’-LT and ‘Right’-RT. .The right connection :

. ' RT uses line 51 and connects via RT line coupler 43. Similarly, die left connection LT uses line 50 and connects via LT line coupler 42. Neither line coupler 42 nor line coupler 43 affects the communication signal. Line . 25 couplers may include connectors, protection devices, isolation (e.g.

trarrformer) and other required functions, which are not normally .

/ associated with die communication signal ifeelf., ;:.,/../ '/׳

׳.\’^: י®.///A transmitter 45, which deals with the data to be transmitted, except for Γ

- the physical layer functions (according to the OSI interconnection model).

?'WO©l/®5®®2 .'. ' '7 <:/'־\ \,7 7? ^!.' . ;/ יPCML©®/®©3g4

7'7 :';'' . ?7 ;.'. .: י י ;77' ;?'7;י.;;' . ?7 'י. 7 /. — 9 — ;?';‘ :71 / ;'?? 7;;7.7 .: י

This blockcan.be implemented in hardware (CRC generation ;circuitry, ־ ; ;7 for example) by software, or by both hardware and software.

® A receiver 46, which deals with the received data, except for the physical layer functions (according to the OSI interconnection model). This block can be implemented in hardware (CRC error detection circuitry, for example),bysoftware,or by both hardware and software.

® A control, logic, and processing unit 47, which controls and monitors

7-'.¹'. '־.''.inode40 ׳. and network operation. This block interconnects with the controlled blocks in node 40 (for clarity, some lines are omitted from

10 Figure 4). In addition, control, logic, and processing unit 47 can process data in the network, and also deals with the payload via payload interface 4§. Control, logic, and processing unit 47 is furthermore in charge of shifting a repeater/router 44 from one state to another, as detailed below.

' 4 ..' Repeater/router 44 deals ‘ with the physical layer characteristics of the cnmrmmication signal. The repeater/router can be in various states, including a receive-only state and a transmit-only state. The signal is . encoded and decoded, and is routed according to the control signals from control, logic, and processing unit 47. Detailed explanation of the '.,’'.';repeater/ro1rter44fbUows.',^^^ /;?

7 A node can be stand-alone or integrated into the payload. For example, in the case of personal computer, the node can be housed within the computer . .7. 7 .־ enclosure as an-add-on card.7 /7’. . ^{; ;}׳- . ; Figures 5a and 5b describe the various repeater/router functions by means of the possible states of a repeater/router during normal operation. As shown in Figure 5a, repeater/router 44 contains two units connected in series. A .? line receiver 44b decodes the communication signal in the line into . a. digital

'.:.'.:.;.?-:signal: which is fed to . receiver 46 for analyzing :the data-link . and higher .OSI. .

. layers. ?The digital signal is .then fed to a line driver 44a; which encodes the ;

:; ftarnrrmni cation signal again. The pair, consisting of line receiver 44b and line .? 30 7? ;?driver 44a thus :form a communication '.signal ?repeater ;which, ?performs a ' . w© M/®5®92 ' : . . ..-' 'A;. .//־:-־/'?. ',; / ;:;i?CTJHLW®®3S4 , .?/:transparent routing of the communication signal..from ‘left’’to '‘right’. ,The־.-. /.-,7 delay between, input and output'is negligible,־ in the order ,of nano-seconds, cr ;

'.־.. micro-seconds. ::'Λ.י';/-. 0/.: ''' ;??,/; .׳

Similarly,. Figinre 5b allows for a routing from ‘right’ to ‘left’. The ' . .5. ., direction of repeater/router 44 is controlled by. control, logic, and processing '.

unit 47, via confrol lines (omittedfor clarity from Figure 5). ,1 . .׳ Whereas. Figures 5a and 5b describe a node which does not generate any . data (but only receives and transfers the data in the network), Figures 5c and 5d ' illustrate nodes in the transmitting state. In both cases, the node transmits data to both the right and left connections via the respective line coupler. In figure ; ־c/twn fine'drivers 44a are used, one for each direction. In figure 5d, .a single line driver 44a is used, driving both directions .from; a .single unit Both embodiments can be used interchangeably. In most cases, the line driver and line coupler characteristics will be the basis for selecting one configuration in preference over the other. For example, if the line driver is capable of driving a single line only, the configuration of Figure 5c should be used.

Figure 6 shows a network .60 according to the present invention.

. Electrically-conducting communication, media of lines '61a, 61b,610, and 61d are used to interconnect the nodes. At least two. conductors are used in the ?0 communication media. For example, coaxial cables or copper twisted-pairs

־.' may be used. For clarity only, the figures herein. illustrate the use of a single ''';../twisted-pafrm.non-lnmt1ngexanq)les.-.:'.'--^:-?..

־/>.'. Nodes 62, 63,/64, 65 and 66 are all the .based on node 40 as described previously.'Nodes 62, 65, and 66 are: in ‘Right to Left’ state as illxistrated in .

Figure 5b, whereas node.64 is in‘Left to Right’ state, as illustrated in Figure ^;5a. Node 63.is the data generating node as in Figure 5c and 5d. The network in ־ _: Figure 6 shows one possible state of the network, wherein node 63 is the data. ־ generating node, while, all other י nodes , serve ' as. receivers and . repeaters, / receiving the data and re-transmitting the data to the next sequential node, hr • WO®l/®5®92 '/.-.Λ '?/?־./ ??/ ?’ ־'< /PCMM®/©®3S4 ׳;.;? ^:;־.ז/;: ^;־? ΓΓ. ^;:‘^f. ;׳.ה.';?.

':? order to support dynamic' reconfiguration, nodes can simultaneously have more' ’ <. . . '.'.. , ‘ . '.;,..־. . .י .'.

than one operational mode. In-a non-limiting fashion, a node can have: .?'.־ ־־ ® .; a data-generating operational mode, wherein, a .node functions as a׳'., source of data, and transmits this data to other nodes; ^; .?' . ־. .:?:.- a receiving operational . mode,_: wherein the., node receives data from' . V/anotiier.node; and .

?,; ;.' ®; / a repeating operational'mode, wherein the node'functions :as׳ a repeater'.' of data received from one given node by re-transmitting this data to .־' another given node.

While the network is functioning, the current operational mode of a node is selectable from the available operational modes. Some operational modes may be mutually exclusive, while others may be selected simultaneously. For example, the data-generating operational mode is exclusive to the repeating operational mode, whereas the receiving operational mode may 15 be selected at the same time as the repeating operational mode.

In most applications, more than one node can serve as a data-generating node at different times. In such a case, the network states will be changed as a function of time according to predetermined logic and control, in order to allow each data generating node an opportunity to transmit However, no more than a 20 single node can serve as data-generating node at a time. While a node is serving as data-generating node, all other nodes states are accordingly set to be repeaters and/or receivers, to allow for data distribution ;along the network. Nodes located ‘left’ ofthe data generating node will be in a ‘right to left’ state, while nodes located ‘right’ of the data-generating node will be in a ‘left to 25 right’state.

. . : It should be clear, that, whereas.the nodes at the network ends, the ‘leftF- G ‘ most’ node 62.and the .‘rightmost’ node 64 could use the same structure as:.

־ shown in Figure 4 (and can be implemented in the .same way as all other nodes .

;?in the network), the end nodes utilize only single line connection.?Thus, these..' .;. Τ ־ : _;. .' /:.ל.'־ ..:.־ >ΡίΠ7ΠΟΚ®324 :ף \Γ;χ end nodes .'can: be: implemented using a :single ;'line: coupler and single ׳line , i_; ; driver. :-::.::.Y :'./.'.י ;.:v/'.: '. '. ׳;' :/.It should, also be clear that one or more of the nodes in the network need:

. riot be connected to: a payload, as .is illustrated for node 65 in Figure.6. This 5 , ' may be the case where the attenuation in the line is too high (e.g. a line is too .:. .long), and.anode serves mainlyas a repeater. In such, a case, payload interface־ 4§ would hot be required. ., . 7

Network powering.

Figure 6 illustrates a network wherein each node is locally powered by a 10 : local power source 52, which supplies electrical power for operating the '.'. .:.:.coi^cnents of the .network. 'Alternatively, the network communication media ' can be used for power distribution. In one embodiment of the present invention, the power is distributed via dedicated lines, such as by the use of two additional wires within the same cable. In a preferred embodiment, tiie same wires can he 15 used for both data communication and power distribution. The latter configuration is described in WO 00/13070 published March 9, 2000 assigned to the present applicant and is applicable to the network discussed herem. Figure 8 illustrates such a network, allowing for single power-supply to be used for powering the whole network.

When the same wires are used for both communication , and power, the node 40 should be modified to include a power/data combiner/splitter 71 as shown in Figure 7. A node 70 is shown/with two power/data combiner/sphtters 71 coupled to line couplers 42 and 43. A node such as node 70 can receive power from either the left or the right sides or &om both sides, and carry the.

power to the non-poweredside. Being powered from the network, no pov׳er ' source interface , w such a configuration. The power

- ־ < source feedmg the ־network?can connect thereto via .dedicated couplers .or via . one ormore of the nodes, modified .to support suchcapabffity._; ,:

. W0®l/05®92 ' 'i-y Jy-A-; > ' /'. - \ i;'.'<' :' '<. PCT/MMMBS4 ;'. Y' ;y '? '.Ϊ'' —13 — λ.;/?.־k<''-' /; A ^;־<; ' y? '׳ - Circular Topology. '.y<.' . . While the foregoing description applies the present invention to a linear . topology, the present invention can also be implemented using a circular topology for ‘ring’ type networks. In. one embodiment, both ends of the 5 network are connected to a node which is configured to receive from both sides, hence including two receivers. However, Figure 8 shows a preferred embodiment of a network SO. In network 80, all nodes except the datagenerating node are configured to the transparent repeater state, either uniformly ‘right-to-left’or uniformly Teft-to-right’. A node 90 in the data10 generating state is modified as illustrated in Figures 9a and 9b. Node 90 can transmit to one side and receive from the other. In Figure 9a node 90 can transmit to the left side and receive from the right side. Similarly, in Figure 9b node.90 can transmit to the right side and receive from the leftside. Either state can be used in circular topology. In Figure 8, node 90 is in the state shown in 15 Figure 9a. Alternatively, node 90 can be in the state shown in Figure 9b. All other nodes of Figure 8 are configured in the ‘right-to-left’ direction. In both cases, the data-generating node 90 transmits to one side and receives from the other. The receiving functionality of node 90 can be used for monitoring the network, to insure that the data path is available and is error-free. However, this 20 receiver functionality is an option only, and does not have to be implemented.

For compactness, Figure 8 demonstrates both the power feeding via the network and the circular topology together, but these features are independent and maybe implemented separately. .

Network Control. y.y.,.'Z: _ ''

As described above; the operation of the network (either bus or circular topology), switches from state to state. Each state is characterized by having a ; specific node functioning as data-generating node at a time, while all other y/y;' nodes serve as^; repeaters and receivers, routing the data, coming from the data־ WG®l/®5®52. .?-'1 :: './ . י.’ -ל י-A 'f Λ ::/- . .;,/'/ ג 'PCWW®©3S4 ' Z&lt;:’ V '.λΧ/''/X'X /X''' ?- 14- ;.-:XX''.X '::'!'׳-generating node. Hence, there is a need for ^:a network controller 'to. determine. ־ , which node, in the network will be the data-generatmg node.

־.. ־ ׳. - Various techniques can be used.to. implement such a network controller. ' . The network controller. can select nodes 'sequentially, :’by. means of token passing.from node to node (similar to that of the Token-Ring network). The. '.

: network controller can be external . , to .the . .network, using’ :dedicated/ communication media. Preferably, the .network, controller will be embedded and win nianage the network states via signals transported by the network itself. In most cases, each node should be allocated an address, enabling data routing in the network from arbitrary node to arbitrary node.

Another popular , method . of network ; discipline is . ‘master/slave’ ־ . operation. In another embodiment of the present invention, one of the nodes will be designated as the master node. In the initial state, this node serves as the data-generatmg node, and while in this state directs other nodes to transmit

During the following state the selected node will serve as the data-generating node. This two-state sequence will be repeated, with a different node selected . :: to be the data-generating node in each subsequent . cycle, 'according to predetermmed logic or under.external control. ’

Dual discipline network.'

The network taught by US Patent 5,841,360 to the present inventor, : herein, referred to as the “PSIC Network”, .employs multiple communication links, independent of each, other. Such, a network supports' several features . which are not available in the previously-described network, such as automatic addressing, fault localization, and circular topology redundancy in the case of single failure. X /.X.

In order to exploit the benefits of both these network types it is possible : :., to׳ cohstruct a network'which, supports bothdisciplines, and can be controlled to /,'be either in one discipline or in theother. For example, the network may start.

&lt; as PSIC. Network. During this start-up period, automatic. addressing and fault⁷;

<img file="IL147407A_D0001.tif" />

;./ ::/ . / י ?&lt; י : /I;׳: . : -15-: /'׳;:??' ./..'Idcalizafipn will.be performed? Thereafter, the network may configure itself to. ?, work according to this application. or' may '.use time-sharing and alternately.

': swritch between both.configurations.

Figure 10 shows a schematic view of a node 100 which is capable of 5 ?? both roles. The state of node 100 is determined by swatches 101,104,102, and ' ; /./103, ?designated SW1, SW2, SW3 and SW4. respectively.These swatches are controlled by control, logic, and processing unit 47. Node 100 employs transmitters 45a and 45b, as well as receivers 46 a and 46b. Line driver 44a './i .'-serves.(^ right port, while line driver 44al; serves the left connection. 10 Similarly, line receivers 44b and 44bL are connected to the right and left?

; ?.'interfacesrespectively. ?''.?. ? ;,. :'^;/?/.

Figure 12 lists the various possible node states for node 100 (Figure 10). '/.?. .'The states in Figure 12 are given in a Node State column, and the swatch settings are given in SW1, SW2, SW3, and SW4 columns. In a ‘Right-to-left’ 15 state, data received in the right port is handled by line receiver 44b and fed to line receiver 46b. Simultaneously, the received data is fed to line driver 44al, which transmits to the left side. Thus, the functionality shown in Figure 5b is obtained. In a similar way, the ‘Left-to-right’ state is implemented to achieve a functionality as shown in Figure 5a. In the latter case, line receiver 46a is the .:'20 active one.

In the ‘transmit both sides’ state, transmitter 45a transmits to both ports rising line drivers '44a and 44al, implementing the functionality shown in ?'?-Figure 5c. In the ‘receive both sides’ state, each receiver is connected to single ^e coupler, m is activated. This is expected to be the state when the network is idle or as an interim state while switching between states, ־?&lt; in ofder to avoid data collisions caused, by two or more transmitters active over ^;T the same link. .ל .-/ ?Τ' ?' ?/.'/.' ?'.^;

/./;/'; -'-.' The ‘transmit right receive, left’ state reflects'the state shown in Figure ././/^ left receive right’ state reflects the functionality / 30 T:;shown in Figure 9a./? .'???/:-' :;';?'-T: ?/.A'?'''' .' ' י' . A.:- /:/ ־ f /¹' ^; WO©1705092 / . .. ' ,. ’&lt;-. ׳

16/4- /-/:.' .-/ ל^:7ל ל >-/'/.: :./:' //////: ’ . :// // : ? / /./ -//.- ?/ ,::- /////.// / - .;

•'/^:;foj1he ^;.^^ sides’, state, ,the.node׳ .can receive and־ / transmit^: in both ’interfaces simultaneously, .thus’ implementing the full PSIC .

.:. :,Network functionality^^ -.- ;.,:7':

׳ . .׳ - ־ ׳: : .׳, : ׳ י י י י ״.׳׳ ,.־ ׳ . ׳׳:׳׳: .

^; Nodes with More than Two Line Connections .5 . - ,Whereas, the foregoing ,discussion describes a node, having two line - couplers (which may be reduced to single interface'in the . case of an end-unit m .

a network employing ‘bus’ topology), it is obvious that three or more such interfaces could also be used. In such a case, at least due additional repeater/rbuter must be added for each additional interface. For example,

Figure 11 illustrates: a node: 110 having three interfaces, where an additional interface is designated as ‘up’, and uses a line coupler 112 for interfacing to a !!J. in order to support the interconnection between all three ports, three repeater/router units 44 are used, each constructed as described previously and suitable for connecting two ports. In some applications, where the connectivity 15 requirements can be reduced, any two out ofthe three ports may be used.

Similarly, additional interfaces can be used. Furthermore, a network can employ nodes of different interface edacities, which, can be freely connected to construct a network of arbitrary topology. In. all cases, the basic rule that each communication link connect only two nodes must be observed.

Furthermore, the network logic embedded in the nodes has to insure that no /'more than a single node generates data, while all others must be in the transparent repeater/router state, directed from the data-generating node.

Implementation.:

: . ' Implementing any of the. above schemes is straightforward :for anyone.

.25 skilled in the art. In one embodiment, RS-405 (EIA-4S5) is employed for. the / / ל ל י physicallayer. In such a case,, line driver 44a and line receiver 44b are .directly’ .- impl em ented using a com men RS-485 line ׳driver or line receiver, respectively.

Similarly;'־'the 7 switches illustrated in׳Figure, 10 can be ;implemented using '/ /&lt; Y relays, .analog switches,, ordigital swiiches/multi. ' 147407/2

PCMM®/®(08S4 . WOW®5®52 ־I־⁷׳ ' plexers. Except in the case of manual switches, switching is controlled electronically.

Repeaters and regenerators are known in both prior-art WAN (Wide Area Network) and LAN (Local area network) systems, mainly for the purpose 5 of allowing operation over lengthy connections. However, there are major differences between those networks and the present invention. First, most priorart repeaters employ single input and single output The present invention / allows for multiple ports. Second, prior-art repeaters are unidirectional, while the present invention is not restricted to a specific direction of data flow. 10 Additionally, the present invention requires a control mechanism (a network controller) for determining the data flow direction, whereas prior-art systems, being unidirectional, do not require such control. In most prior-art networks, units in the network can be clearly defined as either payload-associated units or dedicated repeaters. Such a distinction is not valid when implementing a 15 network according to the present invention, since each payload-associated unit in the network also includes the repeater functionality.

Although a network according to the present invention, when configured in circular topology, can be superficially similar to a Token-Ring network, there are major differences between them. In a Token-Ring network, there is a 20 single constant direction of data flow. The present invention does not impose single direction of data flow, but the flow may change as part of the network operation. In addition, , in Token-Ring networks the data-generating unit is sequentially allocated according to the network topology. In the present invention, the data-generating node need not be chosen according to any 25 specific rule, although sequential selection of the data-generating node is possible.