JPH04323930A - Data transmission system - Google Patents

Abstract

PURPOSE:To reduce interrupt of control and timing deviation on the occurrence of a fault and to improve the safety by allowing a transmitter detecting stop of alternation to bypass a data transferred from other transmitter in its direction. CONSTITUTION:Specific link control information is forwarded and returned between adjacent transmitters and any transmitter inverts a truth value of the information to generate consecutive alternation of the truth value and a transfer path is reconstituted by bypass control when the alternation is stopped. Thus, even when a fault takes place in the transmitter and a transmission cable, since the truth value of link control information sent from a faulty point toward a downward direction is always constant, the alternation is stopped. The action above is obtained how the truth value of the circuit is fixed. The inverting processing of the truth value and an alternation state monitor function are easily realized by the hardware and the high speed operation is attained, then restart on the occurrence of a fault is quickly implemented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loop transmission system, and more particularly to a method for monitoring whether a data transmission path between transmission devices is operating normally and performing detour control.

0002

2. Description of the Related Art Confirming that the data transmission path between transmission devices is normal is a basic procedure for data transmission. One of the methods conventionally used to find out if a data transmission path or the other party's transmission device is down is to send an inquiry signal as to whether communication is possible or not at the start of communication from the transmission device that has issued the communication request. In this method, inquiries are made a predetermined number of times until a response of "Yes" is received.

[0003] Also, there is a method in which during communication, it is detected that signal reception from the other party has stopped for a certain period of time or more, and the inquiry is made a predetermined number of times. Such a determination result is used in each transmission device to indicate a communication abnormality, and in a loop transmission system, it is used to control a detour of a transmission path.

0004

In the conventional systems, the monitoring of data transmission paths with other transmission devices and the subsequent control as described above have been performed exclusively by software. However, this type of operation performed by software imposes a heavy processing load on the processor that controls the transmission device, and has the drawback of causing delays in other processing and reducing the throughput of the effective information amount of the entire transmission network. There are various failure modes that can occur in a transmission system, and the software corresponding to these must be prepared for all possible cases. Therefore, the overhead of case analysis is large and the transition to bypass mode is delayed. If route abnormalities occur repeatedly and sporadically,
The repeated back and forth between detour and normal mode may result in very little time being allocated for normal transmission. Such transmission delays are particularly a hindrance in the transmission of control data where real-time performance is important, such as in factory plant control or transportation control.

[0005] By passing a specific bit back and forth between transmission devices and inverting the truth value of this bit in one transmission device, a continuous alternation of truth values is generated, and a stop in alternation is detected. A method for controlling on the safe side is disclosed in Japanese Patent Laid-Open No. 2-39903.

An object of the present invention is to solve the problems of the above-mentioned detour control methods used in conventional data transmission systems, and to provide a detour control method with high responsiveness and low software burden. be.

[0007]

[Means for Solving the Problems] Therefore, in the present invention, specific link control information is sent back and forth between adjacent transmission devices,
By inverting the truth value of this information in one of the transmission devices, a continuous alternation of truth values is generated, and when this alternation stops, the transmission path is reconfigured by detour control. there was.

[0008]

[Operation] As a result, even if a failure occurs in either the transmission device or the transmission cable, the truth value of the link control information transmitted downstream from the failure point will always remain constant, so the alternation phenomenon described above will not occur. Stop. This effect can be obtained no matter how the truth value of the circuit is fixed. The truth value inversion process and the alternating state monitoring function can be easily implemented using hardware and can operate at high speed, so control can be activated extremely quickly in the event that the transmission path is disconnected.

[0009]

Embodiment FIG. 1 shows an embodiment of the present invention. In this embodiment, the present invention is applied to a loop transmission system for train control, and the loop indicated by the broken line in the figure connects both transmission devices (
ST) represents a logical flow path of link control information between STs. In reality, the data input from the receiving section passes through the processing circuit of the transmission function or the transmission processor, forms a frame with information on the system's applications such as train equipment control, and is output from the transmitting section. . An example of the frame structure is shown in FIG. 2. In this frame configuration, link control information is called a link control section and is placed at the beginning of each word unit to be transferred, followed by a bit group that is an application information group divided into word units. Application information circulates around the entire train along the solid line loop in FIG. 1, while link control information circulates between adjacent transmission STs. Here, one transmission S
Since the link control information is inverted at T, an alternation of truth values occurs as shown in the figure, where one cycle is the time for one round trip of this information through the loop indicated by the broken line in the figure.

The internal operation of the transmission ST will be explained with reference to FIG. In FIG. 3, T is a transmitting circuit, R is a receiving circuit, F1, F
2 is an application information buffer file, 106
1 is an inverting circuit, 107 and 108 are detour switches, 109 and 110 are alternating detection circuits, and 111 is a detour control circuit. The transmitting circuit T transmits application information and link control information together in one word as shown in FIG. The receiving circuit R separates the received word into application information and link control information. The truth value of the link control information on the right side is inverted by the inverting circuit 106 and sent back to the transmission ST that is the pair on the right side, and the link control information on the left side is sent back to the transmission ST on the left side.
Transfer it directly to T. Since the STs on both sides have the same structure, the link control information on the left side is inverted in the ST on the left side. Therefore, if the STs on both sides, the relevant ST, and the transmission paths between them are all normal, the left and right link control information maintains an alternating state as shown in FIG. In this state, the alternating detection circuits 109 and 110 generate a left link detection signal and a right link detection signal, respectively. In response to these signals, the detour control circuit 111 turns the detour switches 107 and 108 in the direction shown in the figure, allowing forward passage of application information. Signals to the onboard equipment group on the car on which the ST is installed are selected from one of the buffer files that stores application information, and signals sent from the onboard equipment to other devices such as the driver's cab are output from the file. The information is expanded and written into the ST, and then transferred to the adjacent ST.

[0011] If a failure occurs at any location in the transmission path or adjacent transmission ST, the link control information after the failure location is fixed to a constant value, so no alternation occurs at any location in FIG. . Now suppose that the transmission path on the right side is cut off. Then, the right link detection signal disappears, and the detour control circuit 1
11, the left side detour switch 107 is turned in the opposite direction as shown in the figure to detour the application information received from the left to the left. Conversely, when the transmission path is restored, the detour switch is restored to its original state.

In the case of the train control system shown in FIG. 1, if the transmission route is interrupted while the train is running and it takes too much time to reconstruct the route, the transmission timing will be delayed or shifted due to the transmission timing of various command signals. Even in a car with a normal ST or transmission path, there is a risk that incorrect train behavior may occur. Therefore, it is desirable that the speed of switching to detouring and restoration be as fast as possible, but among the components of transmission ST,
Since the functions of 06, 109, 110, and 111 are simple, it is easy to operate them at high speed by manufacturing them with hardware.

[0013]

As described above, according to the present invention, it is possible to easily determine the state of a transmission path between adjacent transmission devices in a loop transmission system, and to perform control such as forming a detour at high speed. For this reason, especially in transmission systems used for the purpose of real-time control of trains, etc., it is possible to reduce control interruptions and timing shifts when a transmission line failure occurs.
It becomes easy to ensure safety.

[Brief explanation of drawings]

FIG. 1 is a diagram of a system to which the present invention is applied.

FIG. 2 is a diagram of an embodiment of the invention.

FIG. 3 is a diagram of an embodiment of the invention.

[Explanation of symbols]

106... Polarity reversal unit, 107, 108... Detour switch,
109, 110... Alternating detection circuit, 111... Detour control circuit, F1, F2... Buffer memory.

Claims (1)

[Claims] Claim 1: Repeating alternate transmission and reception of words containing link control information between two adjacent transmission devices in a loop transmission system, and inverting the polarity of the link control information before transmitting this word in one of the transmission devices. One or both of the transmission devices is provided with means for determining the truth value of this link control information, and the transmission device that detects the stoppage of the link control information determines whether the link control information is transferred from another transmission device other than the paired transmission device. A data transmission system that detours incoming data in the direction of the transmission device.