JPH04343543A - Local area network for fa - Google Patents

Abstract

PURPOSE:To attain communication closed in a group and to obtain an FA local area network(LAN) whose response speed is prevented from being dropped by dividing the same bus into plural groups in a bus type LAN. CONSTITUTION:The LAN for FA is provided with a packet transmitting part for specifying a group address to packet destination addresses, simultaneously broadcasting the grouped addresses and filtering a received packet by a group address mask. Low priority order is allocated to simultaneous broadcasting and high priority order is allocated to a transiently generated transient transmission. In addition a management station M3 is connected so as to inform the priority of transmission of the group address, the group address mask and the individual addresses to all stations 2 in the LAN through a transmission medium (cable) 1.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is directed to FA (Factor
Regarding the local area network (hereinafter referred to as LAN) required for
This relates to field nets and cell nets at level 1 (equipment management) and level 2 (station management) in the hierarchy of the rated manufacturing model.

0002

[Prior Art] Field nets and cell nets with bus-type transmission paths have shared data (cyclic data) common to all stations connected to the network, and an update event of the shared data occurs. Sometimes, the station sends data to all stations by broadcast transmission and updates the shared data (sequential click transmission function), and temporarily when there is a communication request from an application of a certain station. Networks that have a function (transient transmission function) for transmitting data by specifying a communication partner are common.

[0003] In a network with a ring type transmission path, shared data is also called cyclic data because it is updated regularly. The shared data indicates information such as ON/OFF of switches on the factory line, timer values, counter values, and operating states of equipment, and must always contain the latest data. Therefore, in order to realize the cyclic transmission function, a real-time communication method is required, and bus-type networks use broadcast transmission to support this.

[0004] In addition, especially in LAN for FA, when viewed from the perspective of factory line system construction, line equipment and control objects become more diverse and complex, and model changes become shorter.
Speed of network construction and ease of maintenance are required.

FIG. 5 is a diagram showing a network configuration in a conventional embodiment. In the figure, 1 is the transmission medium of the bus type LAN (
(cable), 2 is a station connected to a network that performs broadcast transmission or transient transmission, and 4 is shared data of the network.

FIG. 7 shows the IEEE80 system used in this example.
2.4 (token bus) is an explanatory diagram showing the structure of a packet (frame). In the figure, 10 is a packet to be transmitted, 11 is a start delimiter (SD) indicating the start of the packet,
12 is a control unit (FC) that includes packet commands and priorities
, 13 is a destination address (DA) for packet transmission, 14 is a source address (SA) for packet transmission, 15 is a data part (DATA) of the packet, 16 is a check sequence part (FCS) for checking packet transmission errors, 17 is an end delimiter (ED) indicating the end of the packet.

Next, the operation will be explained. In FIG. 5, station A
If an event occurs that updates the shared data 4 at a regular timing, station A updates the data part (DAT) of the packet.
A) Set the shared data update information in 15, specify the broadcast address 13-a in which all bits are 1 as the destination address (DA) 13 of the packet, and transmit the packet. The transmitted packet is notified to all stations in the network (station B, station C, station D, station E, station F) as shown by the arrows in the figure, and the station that received it receives the data part (D) of the packet.
The shared data 4 is updated based on the ATA) 15.

[0008] When a transient transmission event occurs from station A to station B, station A specifies an individual address 13-c whose first bit is 0 and indicates the address of station B as the destination address (DA) 13 of the packet. and send the packet. The transmitted packet is notified to all stations, but station B
The other stations discard the received packet because the destination address (DA) 13 indicates the individual address of station B. Station B receives the packet and reads the data portion (DA) of the packet.
Depending on the contents of TA) 15, the contents are transmitted by specifying the individual address of station A as the destination address (DA) 13, in the same way as the station A transmitted the contents.

[0009] Next, when it is desired to further develop this network configuration and construct a large number of groups with different control purposes on the factory line, the network can be constructed using transmission medium 1 (cable) for each group, as shown in FIG. ) was cut off to allow closed communication within the group.

0010

[Problem to be solved by the invention] As mentioned above, conventionally,
Only one cyclic transmission function could exist on one transmission path, so if there are multiple control targets (groups), each cyclic transmission function must perform transmission for each group so that they do not interfere with each other. However, in the case of complex and large-scale lines with many groups, construction and maintenance of the network requires a great deal of cost and time.

[0011] Furthermore, even if communication equipment used in one group is temporarily used in another group, the cable connection may need to be changed, and if the situation is bad, the equipment may have to be moved. However, there were problems such as lack of flexibility and poor operability.

Furthermore, from the standpoint of response speed of the transient transmission function, conventionally, no particular priority function was provided, so when cyclic transmission occurs frequently, the reception load of the station is increased due to high traffic. This has caused a problem in that there is a delay in response to a request from the other station due to transient transmission.

[0013] This invention was made to solve the above-mentioned problems, and even if the group configuration of a factory network changes, it is possible to group the network without rearranging communication equipment or installing multiple transmission lines. The first objective is to create a local area network for FA that configures logical groups by giving corresponding group addresses and address masks to stations, enables quick and flexible network response, and reduces wiring work. 1 purpose.

[0014] In addition, packets of the transient transmission function are processed with priority over packets of the cyclic transmission function, even when broadcast transmission or multicast transmission by the cyclic transmission function frequently occurs and the receiving load of the station increases. A second object of the present invention is to obtain a local area network for FA that minimizes delay in response to requests from transmitting stations.

A third object of the present invention is to provide a local area network for FA in which the group configuration of the network can be managed remotely and centrally by a management station.

[0016]

[Means for solving the problem] In order to solve the above problem, the transmission path is a bus type, has shared data common to all stations connected to the network, and uses broadcast transmission using a broadcast address. In a local area network for FA that updates the shared data, each station is equipped with a multicast transmission means for simultaneously broadcasting to a specific group using a group address, and a means for filtering received packets using a group address mask. stations are segmented into multiple groups and operated.

[0017] Furthermore, a low priority is given to the broadcast transmission and multicast transmission, which occur relatively frequently.
A high priority is assigned to each temporarily occurring transient transmission using an individual address.

[0018] Furthermore, a management station is provided in the network,
The management station notifies each station of the group address, group address mask, individual address of each station, and transmission priority, and remotely centrally manages the network configuration and transmission control.

[0019]

[Operation] Each station in the LAN according to the present invention specifies a group address as the destination address of a transmitted packet containing updated information on shared data and performs multicast transmission, and the station that receives the packet filters the received packet using a group address mask. Then, only the packets for the group to which the station belongs are taken in and the content of the shared data is updated.

[0020] In addition, a low priority is assigned to broadcast transmission and multicast transmission for updating shared data that occur relatively frequently, and a high priority is assigned to transient transmission that occurs temporarily. Process with priority.

Furthermore, one or more management stations are installed on the network, and the group address operated by each station, group address mask, individual address of each station, and priorities for broadcast transmission, multicast transmission, and transient transmission are connected to the network. Notify all stations that have been registered.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram showing the configuration of a network according to an embodiment of the present invention. A management station M3 and nine stations A to I having shared data 4 are connected to this network. FIG. 3 is an internal block diagram of the station in the embodiment of this invention, in which 4 is shared data, 5 is non-volatile R
AM, 6 is a reception queue for queuing received packets, 7 is a data processing section that executes shared data update processing, etc., and 8 is a packet transmission section that sends and receives packets. FIG. 4 is a detailed diagram of the reception queue 6, showing buffer queues corresponding to eight priorities. In the figure, 10
is a packet. Note that 13-b in FIG. 7 is a group address in which the first bit is 1 and the following 15 bits indicate individual addresses.

The administrator inputs the group configuration information shown in FIG. 2 to the management station M3, and the network is segmented into three groups from the management station M3 as follows. Explain how the system works. First, management station M3
The group address [1100] of group 1 expressed in the format 13-b, the group address mask [11FF], and each individual address [1031] are transmitted from station A, station B, and station C by transient transmission to the data section in the format 13-b. ], [
1032], [1033], the multicast transmission priority, and the transient transmission priority. Each station that receives this stores the instructed group address [1100], group address mask [11FF], individual address, and transmission priority in its internal non-volatile RAM 5, and then transfers its own address to the management station. Update the individual address notified from M3. It is assumed that the management station M3 knows the individual address of each station before it is updated.

The management station M3 uses the same method to send the group address of group 2 [21
00], group address mask [21FF], and individual addresses [2031], [3032], [2033]
and sends the group address [3100] of group 3, group address mask [31FF], and individual addresses [3031], [3032] to stations G, H, and I.
], [3033]. As a result, 9 stations have 3
segmented into two groups.

The operation for group 1 will be explained. When an event occurs in station A to update the shared data, station A sets the update information of shared data 4 in the data section (DATA) 15 of packet 10, and sets the update information of group 1 in the destination address (DA) 13 of packet 10. Group address [110
0] and further specifies the control unit (FC) 1 of packet 10.
Packet 10 is transmitted (multicast transmission) by specifying the lowest priority (PPP=000) for priority PPP 2. The transmitted packet is notified to all stations 2 on the transmission medium, and the packet transmitter 8 of each station filters the received packet according to the following conditional expression.

(Destination address) AND (Group address mask) = (Destination address)

If the above conditional expression does not hold, the received packet 10 is discarded, but if it does, the received packet 10 is temporarily stored in the lowest priority queue of the reception queue 6, and then the data processing unit 7 stores the packet 10. Execute the update process for the imported shared data 4. As a result, group 1
Only stations B and C, which are members of , update the shared data 4. Multicast transmission for groups 2 and 3 also operates in a similar manner to perform independent communication within the group.

Next, when a transient transmission event occurs from station A to station B, station A specifies the individual address of station B as the destination address (DA) 13 of packet 10, and ) 12, specifying the highest priority (PPP=111) and transmitting. The transmitted packet 10 is notified to all stations, but stations other than station B discard the packet 10. The packet transmission section 8 of the station B temporarily stores the received packet 10 in the highest priority queue of the reception queue 6, and then the data processing section 7 takes in the packet 10 and performs transient processing. At this time, even if a plurality of unprocessed packets 10 due to multicast transmission are accumulated in the lowest priority queue as shown in FIG. 4, the data processing unit 8 takes in and processes the packets 10 from the highest priority queue.

Furthermore, in the case of transient transmission, communication across groups is also possible. For example, station A in group 1
The transient transmission from to station E in group 2 is:
This is the same as from station A to station B above.

[0030]

[Effects of the Invention] As described above, according to the present invention, when attempting to construct a bus-type network in which all stations share data by dividing it into multiple groups, there is no need to physically disconnect the network. Because it is possible to construct logically independent networks on the same bus, there is no need to perform wiring work or relocate stations every time the network group configuration changes. Furthermore, communication between groups can be easily achieved using conventional transient transmission, making it suitable for a variety of applications. Furthermore, since the physical network only needs to have one group even if there are multiple groups, it is possible to improve the efficiency of network space.

[0031] Furthermore, even when broadcast transmissions and multicast transmissions occur frequently and the reception processing of a station is under a high load, transient transmission processing is performed with priority, so that the delay in response to requests from the transmitting station is reduced. It can be done very little.

Furthermore, since network group configuration and transmission priority management can be managed remotely and centrally by a management station, network maintenance is easy and even when changes in group configuration occur, it is possible to respond quickly. can.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a LAN in an embodiment of the present invention.

FIG. 2 is a chart showing group configuration information in an embodiment of the present invention.

FIG. 3 is a block diagram showing the internal configuration of a station in an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the structure of a reception queue of a station in an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a schematic configuration of a LAN in a conventional example.

FIG. 6 is an explanatory diagram showing a network configuration when LANs are grouped in a conventional example.

FIG. 7 is an explanatory diagram showing a packet format of the IEEE802.4 standard.

[Explanation of symbols]

1 Transmission medium (cable) 2 station 3 Management Bureau 4 Shared data 5. Non-volatile RAM 6 Packet reception queue 7 Data transmission section 8 Packet transmission section 10 packets

Claims (3)

[Claims] Claim 1: In a local area network for FA where the transmission path is a bus type, has shared data common to all stations connected to the network, and updates the shared data by broadcast transmission using a broadcast address. , each station is equipped with a multicast transmission means for simultaneously broadcasting to a specific group using a group address, and a means for filtering received packets using a group address mask, and the stations on the same bus are segmented into multiple groups for operation. F characterized by
Local area network for A. 2. The system is characterized in that a low priority is assigned to the broadcast transmission and multicast transmission that occur relatively frequently, and a high priority is assigned to the transient transmission that occurs temporarily using an individual address. The local area network for FA according to claim 1. 3. A management station is provided in the network, and the management station notifies each station of the group address, group address mask, individual address of each station, and transmission priority, and remotely centralizes network configuration and transmission control. 3. The local area network for FA according to claim 1, characterized in that the local area network for FA is managed.