JPS6157147A - Loop type data transmission system - Google Patents

Abstract

PURPOSE:To improve the utilizing efficiency by making the relay delay when supervising and relaying are executed as an active set and a signal is relayed as a spare set identical. CONSTITUTION:When a fault is detected by an input signal fault detector 49, a control circuit 32 continues the frame timing received in a frame buffer 44 as it is and uses the timing to constitute a new frame, which is outputted to a transmission line 33 and then to a transmission line 36 via a switch 46, a parallel/serial converter 47, a switch 45 and an output repeater 48. Thus, the transmission signal keeps the timing of the relayed signal frame through a delay circuit 51 so far and each communication controller keeps reception/relay without causing out of synchronism.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switching control system for a monitoring device of a loop data transmission system.

Two or more communication control devices are connected in series through a data transmission path so that the whole constitutes one loop-shaped transmission path (ring-shaped transmission path), and the communication control device is connected to the communication control device via the loop-shaped transmission path. A system for communicating between connected terminal devices is widely known as a loop data transmission system.

In such a transmission system, one monitoring device inserted into the loop-shaped transmission path has a clock source for the signal flowing through the transmission path, generates frames of a predetermined pattern for communication, and controls each communication control. The device performs so-called frame synchronization by detecting a specific pattern in this frame.

In the case of this type of system, if a failure occurs in the monitoring device and it is no longer able to generate the reference information frame, the entire system will be unable to communicate, so two monitoring devices are installed and one is the active monitoring device and the other is the preliminary monitoring device, and when a failure occurs in the active monitoring device, it is switched to the backup monitoring device.In order to reduce communication interruptions at the time of switching, this switching must be done quickly and smoothly. It is necessary that the

[Conventional technology]

FIG. 2 is a block diagram showing an example of a configuration of a loop data transmission system. In the figure, 1 and 2 are monitoring devices;
3 to 7 are communication control devices.

The terminal devices 10 to 16 that communicate with each other through this system are connected to one of the communication control devices.

Each of the communication control devices 3 to 7 and the monitoring device 1.2 are connected in series through data transmission paths 17, 18, 19, etc., thereby forming a loop-shaped transmission path as a whole.

For example, if monitoring device 1 is currently in use, the two monitoring devices are
The monitoring device 2 serves as a backup device, and the backup monitoring device 2 monitors the received signal and relays it as is.

The current monitoring device 1 generates a frame 20 in the format shown in FIG. 3, for example, and sends it to the transmission line 18. frame 20
has, for example, a fixed-length frame header 21 at the beginning, and the frame header 21 is composed of a synchronization code 22 consisting of a specific known bit pattern and a control section 23.
is used, for example, to send and receive commands/responses for monitoring and the like between the monitoring device and each communication control device.

As is well known, when each communication control device detects the synchronization code 22 in the received signal, it counts the predetermined frame length and detects the bit pattern of the synchronization code 22 again at the time position where the next frame is to be received. For example, it is assumed that frame synchronization has been established, and as long as this state continues for wA, communication is performed using the frame.

Once the above conditions are broken, the above synchronization code 2
2 detection operation is performed and communication cannot be resumed until frame synchronization is established. Following the frame header 21 of one frame 20 (the part is divided into, for example, a plurality of fixed length slots 24, for example, when configuring a communication system between the terminal device 10, which is a center computer, and a plurality of other terminal devices, A fixed time position is set for each terminal device 11 as a transmission and reception slot of each terminal device.
~16, and each terminal device communicates with the center using the slot at the time position assigned to itself.

FIG. 4 is a block diagram showing an example of the conventional configuration of the monitoring devices 1 and 2.

The signal from the transmission path 41 is received by the input repeater 42 and converted into a DC signal, assembled into byte data of, for example, 8 bits by the serial/parallel converter 43, and inputted to the frame buffer 44. For example, the frame buffer 44 is 1
It is assumed that it consists of a shift register with a capacity to hold data for one frame.

These circuits are controlled by a clock generated by a clock timing generator 30 in synchronization with the received signal.

The frame counter 31 is reset by the control circuit 32, and by counting a predetermined byte length of the frame, detects a frame break and notifies the control circuit 32 of the frame break.

The data in the frame buffer 44 is sequentially transferred from the beginning to the switching circuit 46 and the control circuit 32. Further, the switching circuit 46 has a transfer line 33 for inputting the output data of the control circuit 32, and which input is passed through is controlled by the control circuit 32 via a control line 34.

The control circuit 32 is, for example, a microprogram control circuit centered on a microprocessor, and controls the entire apparatus.

The control circuit 32 inputs the received data of the frame buffer 44 and performs frame synchronization detection processing, communication processing by the frame header control unit 23, etc., and depending on the results, the frame counter 31 and the black shift timing generator 3
0, controls the switching device 46 and others, and also controls the transfer line 3 if necessary.
Data and the like constituting the frame header 21 are output to the frame header 21.

, switch 46. The output is converted into a bit direct signal by the parallel/serial converter 47, passes through the switch 45, drives the output repeater 48, and is sent to the transmission line 36.

As conceptually shown in the figure, the switch 45 connects the input repeater 4
2 or a parallel/serial converter 47
Under the control of the 1lil control circuit 32, when operating as an active device, the output of the parallel/serial converter 47 is passed to the output repeater 48, and becomes a standby device. If so, the output of the input repeater 42 is directly connected to the output repeater 48.

The input signal abnormality detector 49 is a known circuit for detecting the occurrence of a failure in this data transmission system by monitoring the output signal of the input repeater 42, and the control circuit 32 receives the abnormality detection output and performs a predetermined operation. Controls switching, etc.

[Problem that the invention seeks to solve]

In the above configuration, if a failure occurs in the monitoring device 1 and normal frame transmission is no longer possible, the monitoring device 1 stops transmitting frames and enters a direct communication state.

When the monitoring device 2 monitors the received signal and detects the above state, it becomes the active device and starts transmitting the frame 20.

In this case, since the monitoring device 2 constructs and sends a new frame independently of the monitoring device 1, the timing of the frame that the monitoring device 1 was sending out at -C is not continued, and therefore each communication control As a result of detecting the out-of-synchronization, the devices 3 to 7 must restart the synchronization detection process described above.

For this reason, there is a problem in that when switching of the monitoring devices 1.2 occurs, communication is interrupted for a period of several frames.

[Means for solving problems]

The problem described above is that in a loop data transmission path in which two monitoring devices and two or more communication control devices are connected in series, the monitoring device receives and monitors information frames from one of the data transmission paths. , a monitoring relay means for relaying to the other data transmission path, a signal received from one of the data transmission paths,
delay means for passing to the other data transmission path after a delay time equal to the time required for passing through the monitoring relay means; and selecting the output of either the monitoring relay means or the delay means to select the output of the data transmission path. The problem is solved by the loop data transmission system of the invention having switching means for relaying to.

[Operation] That is, a delay means is provided so that the relay delay of the monitoring device is the same when performing monitoring relaying as an active device and when simply relaying as a backup.

In this way, when the backup device detects an abnormality,
It becomes possible to transmit a frame that is synchronized with the frame that has been transmitted from the current device and whose reception has been monitored, and it is therefore possible to avoid a situation in which each communication control device starts reception synchronization processing anew.

〔Example〕

FIG. 1 shows monitoring devices 1 and 2 showing the configuration of an embodiment of the present invention.
This is a block diagram. In the figure, parts that are the same as those in the conventional example of FIG. 4 are designated by the same reference numerals.

This monitoring device operates in the same manner as described above for the conventional example shown in FIG. It will be done like this.

Therefore, when the input repeater 42 is used as a standby device,
The output is not directly transmitted, but is relayed to the transmission line 36 after a certain delay time by the delay circuit 51.

The delay circuit 51 may be, for example, a circuit configured with a normal shift register and driven by the clock of the clock timing generation circuit 30, and the delay time of the delay circuit 51 is inputted to the serial/parallel converter 43, and then frame buffer 4
4, etc., to the output from the parallel/serial converter 47.

In the monitoring device serving as a backup device, the signal received from the transmission line 41 as described above is sent as is to the transmission line 36 after a certain delay, but at the same time, the signal received from the transmission line 41 is sent directly to the transmission line 36, but at the same time It is assumed that the data reception operation is executed by the circuit shown in FIG.

If an abnormality is detected by the input signal abnormality detector 49 in such a state, the control circuit 32
Continuing the timing of the frame received at
, a switching device 45, and an output repeater 48, and then sent to the transmission line 36.

Therefore, this sending signal retains the timing of the signal frame that was relayed through the delay circuit 51,
Each communication control device 10-18 can continue receiving/relaying without causing synchronization.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to avoid frame synchronization when switching a monitoring device of a loop data transmission system, thereby significantly improving the utilization efficiency of the data transmission system. It has industrial effects.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a monitoring device according to an embodiment of the present invention, Fig. 2 is a side view of the configuration of a data transmission system, Fig. 3 is a diagram showing an example of a frame format, and Fig. 4 is a conventional FIG. 2 is a block diagram of an example of a configuration of a monitoring device of FIG. In the figure, 1.2 is a monitoring device, 3 to 7 are communication control devices, and 10 is a monitoring device.
~16 are terminal devices, 17~19 are data transmission lines, 2
0 is a frame, 21 is a frame header, 22 is a synchronization code, 30 is a clock timing generator, 31 is a frame counter, 32 is a control circuit, 42 is an input repeater, 43 is a serial/parallel converter, 44 is a frame counter , 45 is a cut tA, IB47 is a parallel/serial converter,
48 is the output repeater, second port 5? :3 b

Claims (2)

[Claims] (1) In a loop-shaped data transmission path in which two monitoring devices and two or more communication control devices are connected in series, the monitoring device receives and monitors information frames from one of the data transmission paths, and receives and monitors information frames from the other data transmission path. monitoring relay means for relaying to the data transmission path;
Delay means for passing a signal received from one of the data transmission paths to the other data transmission path after a delay time equal to the time required for passage through the monitoring relay means, and any one of the monitoring relay means and the delay means. 1. A loop data transmission system comprising switching means for selecting one of the outputs and relaying the selected output to the data transmission path. (2) One of the two monitoring devices is a working monitoring device and the other is a backup monitoring device, and the switching means of the working monitoring device selects and relays the output of the monitoring relaying device, and the switching device of the working monitoring device selects and relays the output of the monitoring relay device. 2. A loop data transmission system according to claim 1, wherein the switching means is configured to select and relay the output of the delay means.