JPS60245337A - Disconnection treatment method for ring-shaped dataway - Google Patents

Abstract

PURPOSE:To transmit and receive data normally even at the time of disconnection by sending out a clock as a disconnection identifying signal before it is detected and a transmission line is switched to a loop-back state, at the time of disconnection of the transmission line. CONSTITUTION:When a signal on a transmission line becomes a constant state over a prescribed time or longer, a disconnection detecting circuit 11 decides it to be a disconnection of the transmission line, and outputs a disconnection signal. When the disconnection signal is outputted, a data switching circuit 14 does not output data which has become a constant state but outputs a clock signal to the transmission line through an AND gate AN12, an OR gate OR1, a regenerative repeating circuit 9, a selector 10 and a driver 5 during the time when the transmission line is switched to a loop-back mode. In this way, it does not occur that a station of the downstream side detects a disconnection, and only a station which is the nearest to a disconnection spot is switched exactly to the loop-back mode, therefore, the impossibility of transmission can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical framework to which the invention pertains] The present invention relates to a processing method when a transmission line is disconnected, for example, in a ring-shaped data way that constitutes a distributed process control system.

[Prior art and its problems]

In this type of dataway, it is common to have duplicate transmission paths in order to improve system reliability. Second
The figure is a schematic diagram showing a typical duplex transmission system.

In the figure, ST1 to STn [stations that transmit and receive information, 1 is the regular (main) transmission line, 2 is the backup (
In the sub-transmission lines, data flows in each transmission line are in opposite directions, and as long as the transmission lines are connected normally, data is transmitted via the regular transmission line 1. Here, as shown in FIG. 2, station ST1
If a disconnection accident occurs at point P (marked by , STn enters the loopback mode and forms one ring (loop) using the regular transmission line 1 and the protection transmission line 2, thereby making it possible to continue normal data transmission.

By the way, in a ring-shaped dataway, transmission data goes around from data transmission station to data transmission station by relaying each station in between. Therefore, if a disconnection accident occurs at point P between STl and 5TnO while station ST4 is transmitting data as shown in FIG. 2, the data will be interrupted at STn and not only at station ST1 (ST2 t
' Since the data no longer reaches s'r3, the station ST1 closest to the disconnection point P must switch to loopback mode before station s'r2゜ST3 detects the disconnection and forms a loopback path. For example, a problem arises in that these three stations together form a loopback path, making it impossible to continue normal data transmission.

[Purpose of the invention]

This invention has been made in view of the above problems, and it is possible to prevent multiple stations from going into loopback mode (configuring a loopback path) at 4 o'clock when a transmission line is disconnected. The purpose is to enable normal data transmission and reception.

[Key points of the invention]

In the present invention, when a transmission line constituting a ring-shaped dataway is disconnected, the disconnection is detected and the transmission line is opened until the disconnection is switched to loopback mode.

By sending out a clock as a disconnection identification signal,
Maintains normal data transmission by preventing stations downstream from the station closest to the disconnection point from switching to loopback mode and ensuring that only the station closest to the disconnection point is in loopback mode.
This is intended to improve reliability.

[Embodiments of the invention]

FIG. 1 is a block diagram showing an implementation sequence of this invention, and FIG. 1A #-
1. This is a time chart for explaining the operation at the time of wire breakage in FIG. 1. In FIG. 1, 3 is a main receiver, 4 is a sub-receiver, 5 is a main driver, 6 is a sub-driver, 7 is a demodulation circuit, 8.10 is a selector, 9 is a regenerative relay circuit, and 1lFi.

A disconnection detection circuit, 12 a disconnection output monitoring circuit, 13 a loopback command circuit, and 14 a data switching circuit, these constitute the configuration of each station in FIG. 2. Note that the data switching circuit 14 is connected to the inverter IN.
I, 2, AND gates AN11, 12, 21, 22, OR gates OR1, OR2, etc.

Data from other stations is received via the main receiver 3 or sub-receiver 4, and demodulated by the demodulation circuit 7, respectively. If the transmission path is normal (no disconnection in either the main or sub transmission path), data from the main transmission path (main data) is selected by the selector 8 and taken into an internal logic (not shown). The data demodulated by the demodulation circuit 7 is further modulated by Δ1 through the data switching circuit 14 and sent to the selector 10. The 0 selector lO given to It is output to transmission line 2 and transmitted to the downstream station. Note that among the data output from the demodulation circuit 7, the main data (sub data) is input to the inverter IN.
1 (IN2), Antogame) ANII (AN21)
and OR game) is given to the regeneration relay circuit 9 via ORI (OR2).

Here, the data of main transmission path 1 and sub transmission path 2 (
Assuming that the main data, sub data) are repeatedly turned on and off at least once within a predetermined period of time, the disconnection detection circuit 11 detects the transmission when the signal on the transmission path remains constant for one hour or more. It determines that the line is disconnected and outputs a disconnection m signal. That is, the data (main data) DA as shown in FIG. 11 outputs a disconnection signal DT as shown in FIG. 1A (b). The disconnection output monitoring circuit 12 monitors the duration of each disconnection 1Ii DT, and issues a loopback command request after a predetermined time T has elapsed. Output. When the loopback command circuit 13 receives this command request, it issues a loopback command Is as shown in FIG. 1A (c) to the selector 8.9. As a result, in the case of a disconnection of the main transmission line, as shown in FIG. It is output to the main transmission line 1 via the main transmission line 1. On the other hand, in the case of a sub-transmission line disconnection, the received data DA from the main transmission line is taken into the internal logic via the receiver 3 and is sent to the sub-transmission line 2 via the sub-driver 6. When the data switching circuit 14 outputs the disconnection signal, the data is not changed due to the disconnection.
ANI 2 (AN22) for the time T until the clock signal CLK is switched to loopback mode.
, the OR gate oRt (OR2), the regenerative relay circuit 9, the selector 10, and the driver 5 (6) to output to the transmission path. For example, as in the case of FIG. 2, if a disconnection occurs at point P with station ST4 as the transmission source, disconnection detection is performed at each of stations ST1, Sr1, and Sr1, and the clock signal C is transmitted from each station.
Since LK is sent out, station ST2 p Sr
For 1, this is received as pseudo data, and therefore these stations do not enter loopback mode, but the station s that is closest to the disconnection point P.
As for Tl, since no signal is given from other stations, this station 8
Only T1 will switch to loopback mode.

In other words, as shown in FIG. 1A (d), the main driver 50 output DO receives the received data D from the main transmission line before the disconnection.
A. During the time T from when the disconnection is detected (time 12) to when the loopback mode is switched, the clock signal CLK is output, and after the loopback, the sub-driver 6 outputs the received data DS, so the signal on the transmission line is This means that the partial state of Ml/C does not occur for more than (T+t) time. It goes without saying that if the signal on the transmission line remains constant for a period of time (T+t) or more, the downstream station will go into loopback mode.

[Effects of the Invention] According to the present invention, when a transmission line is disconnected, the clock continues to be sent from the station closest to the disconnection point to downstream stations until this is detected and the transmission line is switched to a loopback state. This eliminates the need for the downstream station to detect a disconnection, and only the station closest to the disconnection point reliably switches to loopback mode, which has the effect of avoiding a situation in which transmission becomes impossible. It is something.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 1A is a timing diagram showing waveforms of each part in FIG. 1, and FIG. 2 is a schematic diagram showing a general duplex transmission system. Code explanation 1...Main transmission line, 2...Song sub transmission line, 3
...Main receiver, 4...Sub receiver, 5...Main driver, 6.Song/sub driver, 7.Song demodulation circuit, 8.10.Song selector, 9・
... Regenerative relay circuit, 11... Open line detection circuit, 1
2... Disconnection output monitoring circuit, 13... Curved loop back finger + circuit, 14... Data switching circuit, s
'rl-s'rn・・・Station, CLK・
...jIIe clock signal. Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyoshi Matsuzaki Figure kA wE 2 Figure

Claims (1)

[Claims] A plurality of stations that transmit information are connected in cascade to each other via two transmission lines consisting of a regular transmission line and a protection transmission line, and if a disconnection rate or failure occurs in at least one of the transmission lines, the transmission line In the ring-shaped dataway that loops back the transmission line, each station includes a detection means for detecting a disconnection of the transmission line, and a loopback forming means for monitoring the disconnection time and looping back the transmission line when the disconnection state has elapsed for a predetermined period of time or more. and signal sending means for sending out a predetermined breakage S identification signal to the transmission line from when the breakage is detected until the predetermined time elapses, and when the transmission line is broken, the A disconnection processing method for a ring-shaped dataway, characterized in that loopback by all stations downstream of the station is avoided by continuing to send the disconnection identification signal for a predetermined period of time from a nearby chain.