JPH0254985B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a communication control system that improves a method for monitoring the status of stations distributed in a distributed manner using a distributed control system connected by communication lines. This invention relates to a communication control system that uses a token pass method as an access control method.

(Prior Art) A distributed control system is a system that reduces the risk of system failure by distributing functions compared to a centralized control system, and has been widely used in recent years. In a distributed control system, a plurality of stations each having a certain function are connected through communication lines. In this type of distributed control system, in addition to sending and receiving information for control, the operating status of each station (normal or abnormal) is
Requires functionality for monitoring. Typically, this monitoring function is located at a station with man-machine interface functionality (monitoring station).

By the way, when monitoring the operating status of each station, the status of the station is whether the data link level is functioning properly or not.
In addition to monitoring abnormal conditions, it is also necessary to monitor the operating state of a processor that performs application-level processing (hereinafter referred to as an application processor). Conventionally, in order to monitor the operating status of an application processor, it has been necessary for a station (monitoring station) having a status monitoring function of each station to perform station status sense communication at regular intervals. Here, station status sense communication means, for example,
An operator console (monitoring station) with a machine interface function sends frame packets called status sense communication to each field control station, and constantly monitors whether these field control stations are operating normally. It is. Whether each field control station is operating normally is determined mainly by the operating state (application level status) of the built-in main processor (including memory, I/O interface, etc.). There is.

(Problem to be Solved by the Invention) According to the conventional station status sense communication method, a sense frame packet is sent to each field control station, and the operating status of these stations is constantly monitored. Since it has to be monitored, it becomes a heavy load on the monitoring station side. Furthermore, this increases the load on the communication line, which impedes effective use of the communication line.
The above-mentioned problems become larger and more serious as the number of stations increases.

The present invention has been made in view of the above points, and an object of the present invention is to make it possible to determine the operating status of each station without using station status sense communication, and to monitor stations and communication lines. The purpose of this invention is to realize a communication control system that reduces the load on computers.

(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, adopts a token pass method as an access method for each station line connected to a bus in a bus-based local area network. , a control field is provided in the token pass frame to carry a destination address indicating the destination of the token, a source address indicating the origin of the token, and a status indicating the operating status of the station, and the data link level of each station is always set to the token. It has a function to capture all paths and create a live list showing the normal/abnormal status of each station from the source address in the frame, and also has a function that allows each communication layer to view the contents of this live list. The token pass frame is provided with a bit that can modify the normal/abnormal state of the application level processor, and the data link level checks the state of the application processor every time the local station issues a token pass frame. The live list is made up of at least two bits: a bit indicating the data link level status for each station and a bit indicating the application level status, and the data link level is changed every time a token pass frame is received. This feature is characterized in that both bits are updated at the same time.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, numerals 10 and 20 are field control stations (hereinafter simply referred to as stations) that constitute a distributed control system. These stations 10 and 20 are interconnected through an external bus (communication line) DB. Although only two stations are shown in the figure, more stations can be connected to the external bus.
Assume that it is connected to the DB. The station 10 includes a main processor 1 that performs various calculation controls.
1. Consists of a memory 12 for storing various data, an I/O interface 13, an input/output device 14 connected to the I/O interface 13, and a communication control device 15 for controlling communication between the station and the outside. ing. These main processors 1
1, memory 12, I/O interface 13, and communication control device 15 are interconnected by an internal bus IB. The above configuration is station 2
The same applies to 0. The operation of the system configured as described above will be explained as follows.

First, it is assumed that line access control in a distributed control system as shown in FIG. 1 is based on a token pass (also known as bunt pass) method. The token pass method is a method in which line control rights (called tokens) are transmitted one after another using command frames (token pass commands) in a predetermined order. In the token pass method, only a station with a token can output a signal on the communication line. When each station receives the token, it sends a command if there is a transmission request, receives a response if necessary, and passes the token to the next station. If there is no transmission request, the station immediately passes the token to the next station. This type of line access is called the token pass method.

In the token pass method, whether the token has been transmitted to the next station is determined by whether a command frame (including the token pass) is sent on the communication line within a certain period of time after the token pass command is sent. . In the distributed control system, there are three ways to connect the stations: star type, loop type, and bus type. The present invention is based on the case of a bus-type connection form.

In the communication control system shown in FIG. 1, each station receives a token in turn and passes the token to the next station to control line access. Figure 2 shows the communication line
FIG. 3 is a diagram showing an example of the structure of a token pass frame output on a DB. In the figure, the preamble (PREAMBLE) is the cue area, F is the flag sequence area, DA is the destination address (DESTINATION ADDRESS) area where the address indicating the destination is stored, and SA is the address indicating the source. C is a control field for packet transmission control, FCS is an area where a frame check sequence is stored, and POST AMBLE is an area indicating the end of a frame. The number shown below each area indicates the number of bits. Note that when data is placed in the frame shown in the figure, the data is inserted between the C area and the FCS area.

FIG. 3 is a diagram showing an example of the structure of the control field C of the token frame described above. In the example shown in the figure, control field C consists of 8 bits, and the seventh bit (shaded area in the figure) contains a model for modifying the normal/abnormal state of the application processor (main processor) 11 of the station. Contains if-bit data. When the seventh bit _D6 is "1", the station is in a READY state, and when it is "O", it is in a NOT READY state. In the token pass method, the D _6- bit data of a normal station is always "1", otherwise it is "0".

As mentioned above, the communication control system according to the present invention performs line access using the token pass method, so one of the stations receives the token, and the remaining stations access the communication line DB. It constantly reads and monitors the bus status. When the communication control device 15 receives a frame on the communication line, it checks whether the frame is a token pass frame. When confirming that the frame is a token pass frame, the communication control device 15 creates a live list indicating the normal/abnormal state of each station from the source address SA of the frame.
The created live list is stored in the communication control device 15.

FIG. 4 is a diagram showing an example of the configuration of a live list. The live list shown in the figure has a maximum configuration of 32 stations, and a 1-byte data area is allocated to each station. A live list is created for each station, and all bytes of a station whose data link level has failed are set to 0. These live lists use a total of two bits, a bit indicating the data link level status and a bit indicating the application level status, as bits indicating the station status for each station.
In this case, bits other than the two specific bits are ignored.

FIG. 5 is a flowchart showing the operation of the system described above. A shows the operation when the token pass frame is sent, and b shows the operation when the token pass frame is received. At the time of transmission, the communication control device 15 sends the token pass frame (see Figure 2).
Enter the next destination station number in the DA area, SA
Write the station number of the source (your own station number) in the field. Next, the application status is received from the application processor (main processor) 11, and when the application processor 11 is in the READY state, it is Hex60, and when it is in the NOT READY state, it is Hex60.
After writing Hex20 into the C area of the token pass frame, send it onto the communication line DB.

Next, the operation at the time of reception will be explained. When the communication control device 15 receives a frame, it first checks whether the frame is a token pass frame. If it is a token pass frame, after initializing the live list for the station between the SA area and DA area in the token pass frame to "0", the contents of control field C are written to the live list corresponding to the SA area. Perform a writing operation.

FIG. 6 is a diagram showing an example of a specific configuration of the communication control device 15 that performs line access control as described above. The device shown in the figure uses, for example, a microcomputer 6800 as a processor.
Components that are the same as those in FIG. 1 are designated by the same numbers.
In the figure, 31 is a processor, 32 is a ROM, and 3
3 is a RAM, 34 is a direct memory access controller DMAC, 35 is an advanced data link controller ADLC, 36 is a coupler that exchanges signals with the communication line DB via an isolation circuit 37, and 38 is an internal bus (system bus) IB. 39 is an interrupt circuit; 40 is a system control circuit that controls the exchange of signals with the
is an MV bus slave circuit, and 41 is an MV bus master circuit. System control circuit 38
The start signal and stop signal from
For example, the data is transmitted to the main processor 11 (Fig. 1) via the IB, and from the main processor 11
It is adapted to receive RUN signals and application status signals.

In the above description, the station 10 was used as an example.
The present invention is not limited to this, and the present invention is not limited to this.
It can be applied in exactly the same way to all stations connected to the DB. Further, the station is not limited to a field control station, but may be a station having other types of functions.

(Effects of the Invention) As described above in detail, according to the present invention, bit data indicating the data link level and application level status of each station is loaded in the token pass field of the line control method of the token pass method. With this configuration, the status of each station can be monitored without performing conventional station status sense communication. Therefore, the load on the monitoring station and communication line can be significantly reduced.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an embodiment of the present invention, Figure 2 is a diagram showing an example of the configuration of a token pass frame, Figure 3 is a diagram showing an example of the configuration of a control field, and Figure 4 is a diagram of a live list. FIG. 5 is a flowchart showing the operation of the system, and FIG. 6 is a diagram showing a specific structure of the communication control device. 10, 20...Station, 11...Main processor, 12...Memory, 13...I/O interface, 14...I/O, 15...Communication control device, 3
1...CPU, 36...Coupler, 38...System control circuit, DB...Communication line (external bus),
IB…Internal bus.

Claims (1)

[Claims] 1 In a bus-based local area network, a token pass method is adopted as the access method for each station line connected to the bus, and the destination address indicating the destination of the token and the token origination are stored in the token pass frame. A control field is provided to carry the source address indicating the origin and the status indicating the operating status of the station, and the data link level of each station always takes in all token paths, and the normal/abnormal status of each station is indicated from the source address in the frame. It has a function to create a live list and a function that allows each communication layer to view the contents of this live list, and the normal/abnormal state of the application level processor is recorded in the token pass frame. The data link level is determined by checking the state of the application processor and modifying the frame every time a token pass frame from the local station is issued, and the live list is configured to modify the state of the data link level for each station. and a bit indicating the application level state,
A communication control system characterized in that the data link level is configured to update both bits each time a token pass frame is received.