JPH0312817B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a control system in a dual loop network consisting of a clockwise loop and a counterclockwise loop. Conventional configuration and its problems Figure 1 shows the configuration of a loop network consisting of clockwise and counterclockwise duplex loops, including multiple stations (ST) 1 to 3 and one center station (ST). CS) 4 (however, it is also possible if there is no center station) and terminals 5 to 12
and clockwise loop 1 that can transmit information independently of each other.
4 and a counterclockwise loop 13. In principle, communication between terminals connected to the same station is performed by forming a communication path within the station or center station, without going through a loop. Communication between terminals connected to different stations takes place via a loop. The information to be transmitted may be synchronous or asynchronous data. In a general loop network, as shown in Figure 1, the hardware is duplicated with a clockwise loop 14 and a counterclockwise loop 13, but normally one of the loops is in a standby state as a backup loop. The signal is transmitted using only one loop. This is to simplify the loop network control method, but the network usage rate during normal times is 1/1.
2, which is very inefficient. Therefore, in order to increase the information transmission speed, data is transmitted using the clockwise and counterclockwise loops at the same time even under normal conditions, and only when one loop fails for some reason, it is switched to the other loop and only one loop is transmitted. In terms of network usage efficiency, it is better to use a method of communicating, then looping back when both loops are disconnected and connecting the clockwise and counterclockwise loops to form a single loop for transmission. However, in this system, the state of the network changes due to failures, etc., such as when the loop transmission mode uses both loops to transmit information at the same time, when one loop is used, or when the loop back is used.
It is necessary to quickly transmit these information to all stations. For this reason, a complicated network control method is required, and there are two possible methods. The first method is to use a normal loop to poll all stations to make inquiries when the network transmission format changes, and to switch sequentially while checking the responses. This system polls each station, so it has the disadvantage that it takes too much time for all stations to recognize the network transmission format. The second method uses a normal loop to simultaneously communicate modes by packet transmission or the like. Even with this method, depending on the station, it may not be possible to receive packets.
It is necessary to confirm normal reception at each station. For this reason, responses from each station are concentrated at the center station,
The processing capacity of the center was exceeded, responses were not processed properly, and the response from the station was timed out, making it necessary to communicate all at once again.
The disadvantage is that it requires a response, and it takes a very long time for all stations to receive the mode correctly. Purpose of the Invention The present invention provides simultaneous transmission in both clockwise and counterclockwise directions as a transmission mode in a double loop network consisting of a clockwise loop and a counterclockwise loop.
When there is clockwise or counterclockwise one-loop transmission, loop back, etc., changes in transmission mode are reliably notified to all stations quickly, minimizing loss in switching time due to transmission mode changes, and The purpose is to limit information transmission to one loop even when both loops are normal, to facilitate various tests on the other loop, and to easily realize loop back control when two loops are disconnected. shall be. Structure of the Invention The present invention has one or more stations that circulate frames at a constant cycle in clockwise and counterclockwise loops, and transmit a code indicating a network transmission mode at the beginning of the frame. In addition, each station is a loop network control system having means for constantly decoding the transmission mode to grasp the transmission mode of the loop network and determining the transmission route. Description of the Embodiment In order to easily transmit real-time audio in a time-division manner in both the clockwise loop and the counterclockwise loop in the duplex loop network as shown in Fig. 1, the second
The frames shown in the figure are circulated at a constant cycle. The frame carries frame synchronization (SYNC), supervisor (SV) that indicates the transmission mode in the loop network as shown in the table below, command (C) that specifies other than transmission mode, and responses from each station. It consists of a response part (R) and data (D) for transmitting synchronous data or asynchronous data. As shown in the table, the transmission mode in the duplex loop is the normal mode in which clockwise and counterclockwise loops are used for transmission at the same time, and in case one loop fails or to test one loop, communication is performed using one route. There are four modes: a right loop mode, a left loop mode, and a loop back mode which is executed when both loops are cut.

[Table] The center station determines the mode based on the state transition diagram in Figure 3, depending on the reception status of clockwise and counterclockwise frames and whether or not frame synchronization is achieved. Set the same mode on the supervisor (SV).
The state of the center station is in four modes as shown in FIG. 3, and the mode changes depending on the combination of clockwise loop normal R, clockwise loop abnormal, counterclockwise loop normal L, and counterclockwise loop abnormal. Note that in response to a test request for one loop from the station, the center station can limit information transmission in normal mode to only one loop that is different from the test request. At each station, frame synchronization is always maintained for both the clockwise and counterclockwise directions, the supervisor is decoded, and the mode in the table in which the loop network is currently operating is determined. In order to prevent the mode decoding output of the station from changing even if the supervisor (SV) makes an error one or two times in a row, the commands from the same supervisor (SV) must be received a certain number of times or more consecutively, or
Measures are taken to receive a certain number or more of the same supervisor commands from among a plurality of frames. Next, we will explain the RAS method using supervisor commands. When the clockwise loop is broken at a certain point A in Figure 1 (one loop), the station that detects the fault notifies the center station using the normal loop. The center station makes a judgment based on the result and the state of out-of-frame synchronization and sets a one-loop designation command in the frame supervisor, thereby allowing each station to transfer information via a normal loop. When both the clockwise and counterclockwise loops are cut at point A in Figure 1 [Loop Back] In both loops, the center station normally sets the frame supervisor to normal mode, so each station
Communicate using clockwise and counterclockwise loops. If both loops were to be disconnected at the same time at point A in FIG. 1, the frames transmitted from both loops would not return to the center station 4, causing frame synchronization. If this continues for a certain period of time or more, the center station 4 considers it to be abnormal and sets the supervisor (SV) from normal mode to loopback mode. As a result, in FIG. 1, the station 2 correctly receives the supervisor (SV) from the center station 4 in the counterclockwise loop, but loops back because there is no signal in the clockwise loop. Similarly, the station 3 correctly receives the supervisor (SV) from the center station 4 through the clockwise loop. However, since the counterclockwise loop signal is cut off, it loops back. On the other hand, at station 1, the supervisor is correctly received by the counterclockwise loop, and there is a clockwise loop signal (it is output from station 2, but the frame synchronization is not achieved), so there is no loopback. In this way, loopback is performed only at the stations 2 and 4 on both sides of the cutting point, forming a single loop. Next, the configuration and operation of the station will be explained in detail. As shown in FIG. 4, the station includes a clockwise loop 15, a counterclockwise loop 16, a left loop controller 30 that controls access to the left loop, a right loop controller 26 that controls access to the right loop,
Terminal interface 27 for interfacing with terminals 29-I to 29-N, internal bus 2
8 and a signal bus 25. The left loop controller 30 and the right loop controller 26 have the same configuration, and each has a receiving circuit 17 that receives signals from the loop transmission path, a frame synchronization circuit 19 that synchronizes frames, a supervisor decoder 20, and a data exchanger with the loop. It consists of an access control circuit 23 for performing access control, a transmission circuit 21 for transmitting data to the loop transmission path, and a loop controller internal bus 24. A frame aligner 18 for adjusting the phase of loop frames and a supervisor command generation circuit 22 for setting supervisor commands are added to the loop controller for the center station. The signal bus 25 is a signal bus used when the station performs loopback. In this way, the left loop controller 30 and the right loop controller 26 can independently control access to each loop depending on the state of the loop, and links between two pairs of terminals can be formed simultaneously via two loops. . The received signal from the counterclockwise loop 16 undergoes clock reproduction and data identification in a receiving circuit 17, and is input to a frame synchronization circuit 19 for frame synchronization. However, in the center station, a frame aligner 18 is inserted to make the delay of one loop an integral multiple of the frame period. The frame synchronized signal in the frame synchronization circuit 19 is output to the loop controller internal bus 24, which is a bus for data and control signals, and is input to the supervisor decoder 20 and the access control circuit 23. The supervisor decoder monitors the supervisor over multiple frames, determines the mode, and notifies the access control circuit 23 of the mode. According to the notification mode, the access control circuit 23 uses the terminal interface 27 to
A link is formed between the terminals 29-I to 29-N, and a communication path between the terminals is formed via the loop by accessing the loop according to a specified procedure. Access control circuit 2
The data from 3 is encoded by the transmitting circuit 21 and sent to the loop. The center station or some stations have a supervisor command generation circuit 22, which generates a supervisor command and then sends it to the transmission circuit 22.
Transferred to 1. The right loop controller 26 also operates in the same manner as the left loop controller 30 described above. Data from the right loop 15 is looped back to the left loop 16, and data from the left loop 16 is looped back to the right loop 15 via the signal bus 25. Effects of the Invention In a duplex loop network system that transmits information by simultaneously using clockwise and counterclockwise loops, there are multiple transmission modes depending on the loop failure situation. is set in the supervisor of a frame that circulates at a constant cycle, and is simultaneously communicated to all stations, so mode switching at the stations can be performed quickly and reliably. In addition, by testing one loop from a state in which both loops are used simultaneously, it is possible to easily shift to one loop communication, allowing for flexible handling of network configurations.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a redundant loop network.
FIG. 2 is a diagram showing an example of a frame configuration in an embodiment of the present invention, FIG. 3 is a mode state transition diagram of the center station, and FIG. 4 is a configuration diagram of the station. 1 to 3...station, 4...center station, 5 to 12...terminal, 13...counterclockwise loop, 14...clockwise loop.

Claims (1)

[Claims] 1. A clockwise loop, a counterclockwise loop, a center station, and a plurality of stations. a first detection means for detecting whether or not the counterclockwise loop is normal; This is a loop network control system having a second detection means for detecting whether the loop is normal or not, and the center station uses the outputs of the first detection means and the second detection means to use both loops. normal mode in which data is communicated simultaneously on each loop, clockwise loop mode in which data is communicated using only the clockwise loop, counterclockwise loop mode in which data is communicated in only the counterclockwise loop, or clockwise loop mode in which data is communicated using only the counterclockwise loop. A mode selection means for selecting one of the transmission modes of a loopback mode in which data communication is performed by forming a loop using a part of the loop and a part of the counterclockwise loop, and a signal indicating the selected transmission mode. Each station receives the transmission mode written in the frame and operates according to the respective transmission mode.In the case of loopback mode, the stations on both sides of the failure point Frames received in the clockwise loop are sent to the clockwise loop, frames received in the clockwise loop are sent to the counterclockwise loop, and frames received in the counterclockwise loop are sent only to the counterclockwise loop at stations other than the stations on both sides of the fault location. A loop network control system characterized in that frames transmitted and received in a clockwise loop are transmitted only to the clockwise loop. 2. The means by which the station decodes the transmission mode is to continuously monitor several frames and determine the transmission mode based on whether the same mode is continuously received a certain number of times or more, or whether the same mode is present a certain number of times or more in multiple frames. A loop network control system according to claim 1, characterized in that: 3 In loopback mode, if a frame can be received in the counterclockwise loop at each station, that frame is sent to the counterclockwise loop, and if a frame can be received in the clockwise loop, the frame is sent to the clockwise loop. Claim 1, characterized in that when only one of the left-handed loop and the right-handed loop can be received, the received frame is transmitted to both the left-handed loop and the right-handed loop. loop network control system.