Multiplex communications – Channel assignment techniques – Polling
Reexamination Certificate
1999-01-21
2001-10-30
Kizou, Hassan (Department: 2662)
Multiplex communications
Channel assignment techniques
Polling
C370S909000
Reexamination Certificate
active
06310885
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a network system comprising one master node and at least one slave node.
BACKGROUND OF THE INVENTION
Hereinafter, a conventional network system will be described.
FIG. 13
is a block diagram illustrating a loop type network system disclosed in Japanese Published Patent Application No. Hei.9-289518. In
FIG. 13
, reference numeral
1301
designates a master node, numeral
1302
designates slave nodes, numeral
1303
designates a token-output/analysis-execution unit, numeral
1304
designates analysis execution units, and numerals
1305
and
1306
designate switches which disconnect the network to make connections to the token output unit and the analysis execution unit, whereby the master node
1301
and the slave nodes
1302
are connected in a loop. The switches of the respective nodes are usually placed at A to connect the network.
The master node
1301
places the switch
1305
at B to select the token-output/analysis-execution unit
1303
, and issues a token packet which specifies a transmission node and a receiving node for data communication. The token packet which has made a round of the loop is discarded by the mater node
1301
, and then the master node
1301
places the switch
1305
to A.
The node which is directed to transmit data by the token packet (transmission node) places the switch
1305
or
1306
at B to output a data packet. When the data packet has made a round of the loop, the node discards the data packet in itself, and returns the switch to A. On the other hand, the node which is directed to receive data by the token packet (receiving node) captures the data packet which is output to the loop-shaped network by the transmission node, into the analysis execution unit
1303
or
1304
.
Data communication between the nodes is performed such that the master node successively outputs token packets.
In the above-described structure, however, since the token packet and the data packet are discarded by the nodes which have output these packets, when the number of nodes connected or the total extension of the loop is increased, the transmission time of the packet around the loop increases, resulting in a reduction in the transmission bandwidth. Further, since the node ID of one node should not be matched with the node ID of another node, management of node IDs is difficult when addition of nodes or the like is carried out.
SUMMARY OF THE INVENTION
The present invention is made to solve the above-described problems and has for its object to provide a network system in which the number of nodes connected can be increased easily without reducing the transmission bandwidth.
Other objects and advantages of the invention will become apparent from the detailed description that follows. The detailed description and specific embodiments described are provided only for illustration since various additions and modifications within the scope of the invention will be apparent to those of skill in the art from the detailed description.
According to a first aspect of the present invention, there is provided a network system comprising a main loop in which one master node, which issues a token packet specifying a transmission node and a receiving node for data communication using a data packet at regular intervals, and at least one slave node are connected in a loop; a first sub loop in which the master node, one sub-master node, and at least one slave node are connected in a loop; and at least one second sub loop in which the master node, at least two sub-master nodes including the sub-master node which is a component of the first sub loop, and at least one slave node are connected in a loop. In this system, the master node comprises a first analysis execution unit which performs outputting the token packet to all the loops, analysis of the token packet, control of data transmission, and data reception, and a first switch which selects one from an output of the first analysis execution unit, an input from the adjacent slave node connected in the main loop, and an input from the sub-master node which is a component of the first sub loop; the sub-master node comprises a second analysis execution unit which performs analysis of the token packet, control of data transmission, and data reception, and a second switch which selects one from an output of the second analysis execution unit, an input from the adjacent slave node connected in the self-loop, and an input from the sub-master node connected in its lower adjacent loop, and outputs it to the master or sub-master node connected in its upper adjacent loop; the slave node comprises a third analysis execution unit which performs analysis of the token packet, control of data transmission, and data reception, and a third switch which selects one from an output of the third analysis execution unit and an input from the network to the slave node; and the first switch, the second switch, and the third switch are controlled to output, transmit, and discard the token packet and the data packet.
According to a second aspect of the present invention, in the network system of the first aspect, the token packet is output from the first analysis execution unit of the master node in the state where the first switch selects the output of the first analysis execution unit, the second switch selects the input from the sub-master node connected in its lower adjacent loop, and the third switch selects the input from the network to the corresponding slave node, whereby the token packet is transmitted to all the loops.
According to a third aspect of the present invention, in the network system of the second aspect, a first specific node, which is directed to transmit data by the token packet, places the first, second, or third switch so as to select the output of the analysis execution unit of the first specific node to output a data packet, transmits the data packet through the master node to all the loops, and discards the data packet which has returned to the first specific node, in the self-node; when the first specific node belongs to the self-loop, the master node and the sub-master node place the first switch or the second switch so as to select the input from the adjacent slave node connected in the self-loop to transmit the data packet, and when the first specific node does not belong to the self-loop, the master node and the sub-master node place the first switch or the second switch so as to select the input from the slave node connected in the lower adjacent loop to discard the data packet input from the slave node connected in the self-loop, in the self-node; and a second specific node, which is directed to receive data by the token packet, receives the data packet output from the first specific node.
According to a fourth aspect of the present invention, in the network system of the third aspect, the token packet specifies either a plurality of receiving nodes or a group ID indicating a plurality of receiving nodes, whereby the corresponding plural nodes receive the same data packet.
According to a fifth aspect of the present invention, the network system of the third aspect further comprises a branch unit disposed between an output end of the master node and all the loops, the branch unit analyzing the data packet and transmitting the data packet to all the loops when the data packet is not a node ID setting packet from the master node, while transmitting the data packet to one of the loops when the data packet is a node ID setting packet from the master node. In this system, the master node, the sub-master node, and the slave node have a common initial node ID, and when the master node outputs a token packet which specifies the initial node ID for both a transmission node and a receiving node, all of the nodes having the initial node ID place their switches so as to select the outputs of their analysis execution units and, in this state, the master node outputs the node ID setting packet as a data packet, whereby only one node amongst the nodes having the initial node ID recei
Ikeda Toshihisa
Mizuguchi Yuji
Moriguchi Ken-ichi
Sakai Takahisa
Elallam Ahmed
Kizou Hassan
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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