JPS5910104B2 - Data transmission method for multiple loop transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a transmission method of a multiplex data transmission device for process control, and the present invention relates to an improvement of a transmission method of a multiplex data transmission device for process control. Regarding transmission method.

In recent process control systems, there has been a shift from a centralized control system using a large control computer to a distributed control system in which a large number of dedicated control devices are arranged for each area, with the control computer at the center.

Background to this is control technology that has become more sophisticated and complex, and it has become important to efficiently connect these control computers and process control devices. Conventionally, in such a distributed control system, a circular data transmission device as shown in FIG. 1 has been used to establish a data link between a central computer and control devices in each area.

However, as control systems become larger in scale, the amount of information transmitted over the transmission path increases, and the transmission capacity (unit:
Along with the desire for transmission equipment that can transmit a large amount of information (transmitted information per unit of time), it is also necessary to layer transmission equipment, in which transmission equipment dedicated to each area is connected to the core transmission equipment, as shown in Figure 2. It's coming. If we try to realize this layering simply by combining conventional transmission equipment, a transmission control station (station) that connects the main transmission line and the branch transmission line
In this case, it is necessary to carry out double processing for the transfer of both, and it has been difficult to create an efficient Yukura due to the response speed and the complexity of the software transmission processing. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to facilitate the transmission processing at the combining station and minimize the transmission time when a large number of transmission paths are combined and data transmission is performed over two or more of the transmission paths. It is an object of the present invention to provide a data transmission method for a multi-loop transmission device without the above. The present invention will be described below based on an embodiment shown in the drawings.

FIG. 2 shows the configuration of a control system using the multiple loop transmission device of the present invention, in which stations 31 to 35 in the transmission line 40
Considering the communication between them, it can be carried out in the same way as the conventional transmission method shown in FIG. In this case, a group of signals transmitted from a transmitting station is called a frame, and generally contains information as shown in FIG. SA is the secondary station (receiving station) address, C is the transmission control code,
PA is the primary station (transmission station) address, AD is the storage memory address or output device address on the secondary station side, N is the number of transmitted data, D is the net data, and CHK is the error check code. In addition to the above, codes for controlling the transmission line are also necessary, but they are not directly related to the present invention and will therefore be omitted.

Normally, this information is sent from the primary station indicated by PA to the secondary station indicated by SA, and the response frame shown in Figure 4 is sent back from the secondary station to the primary station, completing one transmission. end. In the case of FIG. 4, part C is a response code such as an acknowledgment (ACK) or a negative acknowledgment (NAK) of the transmission control codes. Here, FIGS. 3 and 4 show only the contents of information necessary for transmission, and the length (number of bits) of this information is not particularly limited. Next, a transmission method via multiple loops according to the present invention will be explained.

As a condition, it is necessary to allocate a loop address (LA) to each of the main loop and branch loops.

Now they are loop 40, loop 41 in FIG.
LA of loop 42 and loop 43 are 40 and 41, respectively.
, 42, 43. The contents of transmission frames between multiple loops are determined as shown in FIG. In Figure 5, SA and PA have the same meanings as in Figure 3, but
In this case, it always indicates the SA and PA within the loop in which the frame is currently being transmitted. Therefore, when the transmission loop changes, the contents of SA and PA also change. C is also the third
Although the transmission control code is determined in the same way as the one in the figure, a code specifically indicating that the frame passes through multiple loops can also be added to distinguish it from transmission frames within a single loop. Further, LN indicates the total number of loops passed through, LC indicates the number of loops that have been transmitted, and LC increases by 1 when the transmission of one loop is completed.

Therefore, for frames in which the value of LN and the value of LC are equal, it is determined that the loop currently being transmitted is the final loop.
The following LA, , SAl indicate the loop address in the first loop and the secondary station address, respectively. Next LA2
, SA, and thereafter, the LA and SA of the loops to be passed through will be shown in order up to the final loop. In Figure 5, the third
Since the th loop is the final loop, LA,,SA3
However, the number is generally arbitrary. Of course, it is necessary to determine the initial ZLC value depending on the number of loops. The response frame is the same as that shown in FIG. 4, and the response frame is returned for each transmission within one loop to terminate the transmission. As a specific example, in FIG. 2, data transmission from the process control device 20 to the process control device 25 is shown as follows.

1 1st loop repro? Station 50 coupled to controller 20
The frames sent out on the loop 41 are as shown in FIG.

In the first loop, SA=33, PA=50, LN=3, L
C=1, LA1=41, SA1=33, LA2=40,
SA,=34, LA3=42, SA3=55. Other information C, AD, N, D, and CHK are determined without being directly related to the present invention, so they are not specifically shown. Since SA=33, station 33 receives this frame.

After error checking, the response frame as shown in FIG. 7 is looped 41.
The signal is sent to the ground, and the transmission in the first loop is terminated. 2 Second loop: Station 33 can determine that the frame should be transmitted to the next loop because it is LNXLC of the received frame, increases the LC value by 1, and places the frame shown in FIG. 8 on loop 40. Send out.

In the case of this second loop, SA=34, PA=33, L
N=3, LC=2, LA1 and later are the same as the first loop. Regarding the response, as in the first loop, the station 34 outputs the frame shown in FIG. 9, and the transmission in the second loop ends. 3 third loop; station 34 is LN'S. Since it is a LC, it is determined that the frame should be transmitted to the next loop, and the LC
is incremented by 1 and the frame shown in FIG. 10 is sent onto the loop 42.

In the third loop, SA=55, PA=34, LN=3, L
C=3, LA, and the rest are the same as in the first loop.
Since LN=LC, this loop is the final loop, and the station 55 returns the response frame shown in FIG. 11 on the loop 42 to terminate the transmission, and the process controller 2
Transfer data to 5. As shown in this example, according to the present invention, transmissions that occur in multiple loops are unified and performed up to the final destination, so processing at the relay point is simple and the time is reduced to 5.

In the explanation so far, the transmission lines have been described as having a loop configuration, but as shown in FIG. 12, the branch transmission lines 41 to 43 may have a party line configuration, and any other transmission The present invention can be applied even to roads.

The simplest type of multiple loops is a two-loop combination configuration, and if the application of the present invention is limited to the two-loop combination configuration,
From the 3-loop combination configuration frame in FIG. 5, LN, LC,
LAl, SAl, LA2, LA3, and SA3 can be omitted. That is, as shown in FIG. 13, only the destination station address on another loop is sufficient as the inter-loop coupling information. In this way, according to the present invention, it is possible to provide an effective data transmission method for a multi-loop transmission device in which the transmission process at the coupling station is easy and the transmission time is reduced.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a control system using a conventional single-loop transmission device, FIG. 2 is a configuration diagram of a control system using a multiple-loop transmission device showing an embodiment of the present invention, and FIG. 3 is a configuration diagram of a control system using a conventional single-loop transmission device. 4 is a diagram of the response frame structure of the conventional and the present invention. FIG. 5 is a general configuration diagram of the transmission frame structure according to the present invention. FIGS. 6 to 11 are specific examples of the present invention, and each loop 12 and 13 are diagrams showing other embodiments of the present invention. 11-12... Control computer, 20-29...
... Process control device, 31 to 35 ... Station on the backbone transmission path of the data transmission device, 4
0 to 43...Transmission line portion of data transmission device, 5
0 to 59... Station on the branch transmission path of the data transmission device, SA... Secondary station address, C... Transmission control code, PA... ...Primary station address, LN...Number of loops to be routed, L
C...Transmitted loop count value, LAO...
・nth loop address, SAO... nth
Secondary station address on the second loop, AD... Data storage address or equipment number at the final destination station, N...
...Number of transmitted data, D...Net transmitted data, CHK...Error check code.

Claims (1)

[Claims] 1. In a multiplex data transmission device for process control that combines multiple transmission paths, the station identification number and the identification number of each transmission path are determined, and the number of transmission paths passed through and the total number of transmitted transmission paths are specified in the transmission frame. It transmits information including the numerical value, the identification number of all the transmission lines passed through, and the secondary station number on that transmission line, and increases this transmitted transmission line count value every time transmission on one transmission line is completed. At the same time, a data transmission method for a multi-loop transmission device configures a new transmission frame by setting a primary station number and a secondary station number from information in the own frame for transmission on the next transmission path.