JPH1188387A - Loop type transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unstableness of a communication condition and to attain conversion under a stable condition by detecting a fixed abnormality between neighbor stations by a response frame from the neighbor station, counting for a fixed time the number of abnormal frames a node receives, detecting that there is an abnormality between neighbor stations when the value exceeds a threshold and detecting an offset of abnormality generation by a division of a monitoring time. SOLUTION: A loop control part regularly transmits an intrastation condition confirmation frame to a transmission line side that is in terminal station mode. To this, a neighboring node sends back a response frame. A response frame check circuit 200 of a restoration counter confirms that this response frame returns and if a bit pattern that consists of the response frame is normal. A normal completion signal when it is normal and an abnormal completion signal when an abnormality is detected are transmitted to a counter 201. The counter 201 counts up with the normal completion signal and is cleared by the abnormal completion signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cascade connection of a plurality of control devices on a ring via a transmission line to mutually transmit data, and an abnormality has occurred in the transmission line or a part of the control device. The present invention relates to a loop-type transmission device that reconfigures a system so that a total function stop does not occur when the system is stopped.

[0002]

2. Description of the Related Art In a time-division data transfer apparatus, as a method for accessing the medium (media access method), IEEE802.3 (CAMA / CD) or IEEE82.3 is used.
02.4 (token bus). In particular, in a system in which responsiveness is emphasized in industrial use, the latter token passing method for transferring a token (transmission right) is often used because of its definite responsiveness.

[0003] The token bus has a bus-type topology because it is intended to use an electric cable such as a coaxial cable. However, if a failure occurs on a transmission line, all systems cannot communicate with each other. In addition, there is a problem that it takes a long time to restore the function because it is difficult to identify and isolate an abnormal part.

A means for solving this problem is to adopt a loop topology in which communication with an adjacent node can be confirmed. In this case, in order to change from the bus configuration to the loop configuration, there is a problem of how to delete data that returns in one cycle.

A solution to this problem is the first described below.
Of the related art [Japanese Patent Laid-Open No. 62-212236 (data transmission device)] and the second related art [Japanese Patent Application No. 7-530].
No. 17 (data transmission device)] and a third prior art [Japanese Patent Application No. 7-238872 (loop type transmission device)].

In the first conventional technique, a switch node is provided in a system, and a received signal is not repeated in a normal state but is repeated when an abnormality is detected.

In the second conventional technique, an abnormality is detected not by the switch node but by a response frame from an adjacent node at the time of transmission / repeat of a general node and an adjacent node upon detection of no signal. An abnormality is detected by monitoring a response frame to the status confirmation frame transmitted by the terminal, transmission and repeat of the information frame to the abnormal side are prohibited (terminal mode), and the switch node is notified of the abnormality, and then periodically. Then, an adjacent station status confirmation frame is transmitted to the adjacent node on the abnormal side, and a response frame corresponding thereto is returned, thereby detecting the recovery on the abnormal side.

[0008] Further, with this alone, there is a possibility that disconnection and recovery by the above-described failure detection are repeated for a failure in an unstable state. The third conventional technique solves this problem. The third conventional technique counts the number of normal frames and abnormal frames of information frames to be received. The receiving side is shifted to the terminal station mode, and even if an unstable failure such as poor contact of a connector occurs, the portion can be separated to stabilize the system.

[0009]

In the first and second prior arts described above, by changing the bus type data transmission device to a loop type topology, it is possible to isolate a faulty portion. The conventional technology has made it possible to determine an unstable failure point.

However, these first to third prior arts add a method of restoring a part separated by frequency-based failure detection, a method of changing a judgment condition in each applied system, and a method of frequency-based failure detection. Nevertheless, there is a shortage of a process when the unstable state continues and a method of realizing a failure determination at high speed.

The present invention has been made based on such circumstances, and when disconnection is performed at the frequency of occurrence of an abnormality, the bias of failure occurrence is determined, and the disconnection / recovery operation is repeated by setting a recovery condition in accordance with the failure. It is an object of the present invention to provide a loop-type transmission device that can prevent the communication state from becoming unstable and converge to a stable state as a result.

[0012]

In order to achieve the above-mentioned object, the invention according to claim 1 is directed to a method for transmitting and receiving data in both directions and repeating the data in a direction opposite to the side receiving the data to be received. Are cascaded in a ring by a pair of transmission lines through which data flows in opposite directions, at least one of the plurality of nodes is always prohibited from being repeated, and a transmission line from another node is When a terminal notification frame for notifying the abnormality is received, the repeat is started, and when a recovery notification frame for notifying the transmission path recovery from another node is received, a reset frame is sent to initialize all nodes in the system, In a loop-type transmission device including a terminal node configured to return itself to a repeat state, the node detects whether a signal is transmitted from its own station or no signal is detected. First abnormality detecting means for detecting a fixed abnormality between neighboring stations in a response frame from the neighboring station to a neighboring station status confirmation frame issued to the node, and counting the number of abnormal frames in the frames received by the node for a predetermined time A second abnormality detecting means for detecting that there is an abnormality between adjacent stations when the number of abnormal frames during the certain time exceeds a threshold value; and a division time obtained by further dividing the monitoring time of the transmission frame into a plurality. And a loop-type transmission device provided with a third detection unit that detects a bias of the occurrence of an abnormality by observing an abnormality that occurs in the loop.

According to the first aspect of the present invention, the node periodically monitors the normal / abnormal counter of the transmission frame, and when the number of occurrences of the abnormal frame exceeds the threshold value, determines that the transmission line side is abnormal, and performs transmission / reception. Prohibited (terminal mode),
The terminal notification code is notified to the at least one existing switch node of the system using the transmission on the opposite side.

With the first detecting means, an abnormal part can be separated from the system at a high speed with respect to a fixed abnormality such as a disconnection or a neighbor station down. By the second detecting means, an unstable portion can be separated from an unstable state such as a contact failure of the connector, thereby stabilizing the system.

The third detecting means makes it possible to know the bias of occurrence of an abnormality, and thereby determines the minimum monitoring time for confirming the recovery. That is, if at least one abnormality has always occurred in each of the n divided times, the monitoring time for judging the recovery is sufficient to be t / n. If there are a, there is a need to monitor for t / n × (a + 1) in order to determine recovery.

To achieve the above object, the invention according to claim 2 is characterized in that the third detecting means changes the return condition of the abnormal part according to the reason for judging the separation of the abnormal part, and changes the return condition according to the adjacent station state confirmation frame. In the case of disconnection due to error, it is determined that the recovery has been performed a fixed number of times.In the case of exceeding the threshold of the number of abnormal frames, recovery is determined to be continuous if recovery detection continues normally for a certain number of times or more according to the frequency of occurrence of errors and its bias. ,
2. The loop-type transmission device according to claim 1, wherein the loop-type transmission device prevents a repetition state of the disconnection recovery operation from continuing.

According to the invention corresponding to claim 2, when the terminal station mode is set at the frequency of occurrence of an abnormal frame, a set value is received as a condition for restoring during the monitoring time determined in claim 1. Use the total number of abnormal frames. As a result, when the abnormality at the same level as the condition for entering the terminal station mode disappears, the restoration notification is sent to the data processing unit and the disconnection and restoration are not repeated.

[0018] In order to achieve the above object, the invention according to claim 3 counts the number of times of disconnection and restoration,
Monitor whether disconnection and recovery operations are performed repeatedly within a certain period of time, and if it continues more than a certain number of times, completely stop the recovery process on the side that is repeating the abnormality and recovery to stabilize the system 3. The loop type transmission device according to claim 2, wherein

According to the invention corresponding to claim 3, the number of times of disconnection (terminal mode) and the number of restoration processes for each system are monitored at a cycle larger than the cycle of claim 2. As a result, the abnormal system can be fixed to the terminal mode so that the above-described processing is not repeated for a system that is not stable even in the method of the second aspect.

In order to achieve the above object, the invention according to claim 4 is characterized in that, when the no-signal is detected, a plurality of frames of the inter-station state confirmation frame are transmitted in a short time to check the line state immediately. A loop-type transmission device according to claim 1.

According to the fourth aspect of the present invention, it is possible to transmit a large number of neighboring station state confirmation frames in a short time and to surely grasp the state of the transmission path. According to the invention corresponding to claim 5, in order to achieve the above object, the cause of disconnection to the higher-level external device connected to each node, the count value of the abnormal frame and the normal frame to be received, the disconnection 2. The loop-type transmission according to claim 1, wherein a threshold value of the abnormal reception frame, a detection time interval, a threshold value of the separation / recovery count, and a monitoring time thereof can be set by reading the number of times of recovery / recovery. Device.

According to the fifth aspect of the present invention, the abnormality monitoring time and the threshold value of the first aspect are received from an external device.
By setting a monitoring cycle and a threshold value of each node, and by making it possible to refer to the current frequency of occurrence from the node, it is possible to carry out settings according to the system.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. (Structure of Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a system configuration diagram showing a first embodiment of the loop type transmission apparatus of the present invention. In this transmission system, a plurality of transmission nodes (STN: transmission stations) 2a, 2b, 2c, 2d,.
Are connected in a distributed manner, and the transmission nodes 2a to 2n
Includes external devices 3a, 3b, 3 each comprising a PLC (programmable logic controller), a computer, a personal computer, an I / O device, and other control devices.
, 3d,... 3n are connected.

The transmission nodes 2a to 2n described above have the same configuration and are connected to a data processing unit 4 for performing transmission / reception data processing, RAS (row address strobe) processing, and an external device 3, as shown in FIG. Interface unit 6 for performing access control, a media access control unit (MAC) 7 for controlling access to a transmission medium, a loop control unit (LP) 8 for controlling a loop line, a transmission / reception circuit for converting a logic signal and a transmission signal 10, a frame counter (CNT) 9 for counting the number of normal / abnormal frames of both transmission paths independently of the LP8, and counting up each time the restoration confirmation processing from the LP8 is performed normally, and the confirmation processing is performed even once. Clears the count value when detects an error, and issues an interrupt to the data processing unit when the count value reaches the value set by the data processing unit. Made from the recovery counter 20 to be,
Details of the recovery counter 20 will be described later.

The data processing unit 4 includes a CPU (arithmetic processing unit) 41 including peripheral circuits for performing transmission / reception data processing and line control processing, and an internal bus 5 derived from the CPU 41.
And a memory 42 composed of a ROM for storing operation programs and other necessary programs and a RAM for temporarily storing processing data.

The device interface unit 6 is connected to the bus 15 and the internal bus 5 from the external device 3, and outputs an interrupt signal 61 to the external device 3 and the CPU 41. A dual-port memory 62 is connected to the bus 13 and the internal bus 5 and is accessible from both the external device 3 and the CPU 41.

Here, the MAC 7 is connected to the internal bus 5 and outputs a control signal 11 for controlling transmission / reception timing. LP8 is the internal bus 5
To monitor / control the state of communication with the adjacent station, select the received frames 12 and 13 from both sides, and send them to the MAC 7. The transmission / reception circuit 10 converts a signal level on the transmission lines 1a and 1b in a double loop configuration with the logic signal.

The CNT 9 is transmitted from the transmitting / receiving circuit 10 to the LP.
8 to detect the number of abnormalities by monitoring the received signals of both systems. FIG. 3 is a block diagram showing a schematic configuration of the recovery counter 20, which is configured as follows and shows a circuit on one transmission line side.
Has two such circuits. The recovery counter 20 is L
A response frame check circuit 200 for monitoring a neighboring station status confirmation frame sent from P8 and a response frame returned from the neighboring node to determine normal / abnormal, and a check circuit 2
A counter 201 that counts up with a normal completion signal from 00 and clears with an abnormal completion signal, a register 202 that stores a set value set from the data processing unit 4, and compares the counter value with the register value to determine the counter value. A comparison circuit 203 generates an interrupt to the data processing section 4 when the register value is reached.

FIG. 4 shows a no-signal monitoring timer circuit provided in the loop control circuit LP8. An additional monitoring timer circuit 51 is added to the conventional monitoring timer circuit 50. These timer circuits 50 and 51 are also prepared for each transmission path system. Conventionally, a received signal enters the first monitoring timer circuit 50, and when the time is up, a time-up signal is output to a neighbor state confirmation signal sending circuit (not shown).

In the present invention, the additional monitoring timer circuit 51 for inputting the received signal in parallel, the additional monitoring timer circuit is enabled by the time-up signal of the conventional monitoring timer circuit 50, and the number of times the additional monitoring timer circuit 51 has timed up is counted. (CNT) 52, and an OR circuit 53 that performs a logical OR operation on both time-up signals.

(Operation of Embodiment) (1) Failure Detection and Recovery Using Response Frame LP8 monitors response frames from adjacent nodes at the time of transmission and repeat of its own node. If this response is not returned, it is determined that there is an abnormality between the adjacent nodes, and transmission is prohibited and the signal repeat is prohibited (terminal station mode) on the transmission line side. Thereafter, the adjacent station status confirmation frame is periodically transmitted to the transmission line determined to be abnormal, and the response frame is monitored. If the response frame is returned, it is determined that recovery is to be performed, and the data processing unit 4 is notified of recovery. For this behavior,
The detailed description is omitted since it has already been filed in Japanese Patent Application No. 7-53017.

(2) Failure detection and recovery by abnormal frame counter The frame counter 9 counts the number of normal / abnormal received frames for each system. The data processing unit 4 monitors the numerical value of the frame counter 9 and does not exceed the threshold value of the number of abnormal frames set from the external device 3 within a period designated by the external device 3 via the device interface unit 6. Check continuously. At this time, the data processing unit 4
Divides a designated period T1 into n equal parts, performs sampling for each of the n equally divided periods t1 to tn, and records the number of individual normal / abnormal frames.

When the threshold value specified in the period T1 is exceeded,
The data processing unit 4 determines that the transmission path side is abnormal and shifts to the terminal mode as in the case of the failure detection and recovery using the response frame of (1) described above.

Here, the data processing unit 4 prohibits the recovery interruption from the LP 8, sets a comparison value in the register 202 of the recovery counter 20, and permits the recovery notification from this circuit. The comparison value to be set is determined as follows. Basically, a period in which at least one abnormality occurs in the state in which the terminal mode has been shifted is found, and it is confirmed that the recovery detection corresponding to the period is normally completed without any abnormality. When an abnormal frame is detected in all of the divided periods t1 to tn, the period in which the minimum abnormal frame is detected is to be compared. If there is a period during which the number of abnormal frames is not detected, this period is also added. If the same number of normal reception frames as the number of frames received during this period can be continuously detected, at least the condition for transition to the terminal station mode has been cleared.

Specific examples are shown below. Assuming that the threshold value of the number of abnormal frames in the period T1 is N, each divided period t1
Assuming that the number of normal / abnormal times from 1 to tn is 1i to mi, respectively, if the minimum number of frames shown below is continuous and normal, it means that the condition transferred to the terminal station has been cleared.

Minimum monitoring frame number = Σ (1i + mi) (i is a period in which mi is 0 and a minimum value other than 0) In practice, the minimum monitoring frame number is multiplied by a safety factor and used.

The LP 8 periodically sends an inter-station state confirmation frame to the transmission line side in the terminal station mode. In response, the neighboring node returns a response frame. The response frame check circuit 200 of the recovery counter 20 confirms that this response frame is returned and whether the bit pattern constituting the response frame is normal. If normal, a normal completion signal is sent to the counter 201, and if abnormality is detected, an abnormal completion signal is sent to the counter 201. Counter 20
1 is incremented by a normal completion signal and cleared by an abnormal completion signal. The count value of the counter 201 and the set value from the data processing unit 4 stored in the register 202 are compared by a comparison circuit 203. When the normal number of response frames from the adjacent node reaches the set value, the internal The data processing unit 4 is notified via the bus 5 that the system is stable.

The data processing unit 4 thereby requests the reconfiguration of the system of the switch node in the system in order to release the terminal mode, and the system is initialized by the reset frame issued from the switch node.

(3) Stabilization by monitoring the number of disconnections / returns Even if the abnormal frame is monitored, there is a possibility that an unstable state in which disconnection / recovery is repeated may occur depending on the frequency of occurrence of abnormalities and the occurrence bias. On the other hand, the data processing unit 4 periodically checks the number of disconnections / returns, and if the number exceeds a certain number, the transmission line side is fixedly fixed to the terminal mode.

Thereafter, the recovery detection is stopped and the system is stabilized. (4) High-speed judgment method at the time of detecting no signal LP8 monitors the no-signal state of the transmission lines 1a and 1b, and upon detection, sends out the adjacent station state confirmation frame to the detected transmission line, and the adjacent node is normal. To determine if it exists. Here, in order to surely confirm the existence, once a no-signal state is detected, and once the neighbor station state is detected, a plurality of the neighbor station status confirmation signals are transmitted in a short term.

This is because the received signal is transmitted to the conventional monitoring timer circuit 5.
0, an additional monitoring timer circuit 5 provided for the present invention.
1 so that the counter 52 can be monitored by the additional monitoring timer circuit 51 when the conventional monitoring time is up.
Is allowed. The additional monitoring timer circuit 51 is set to a shorter monitoring time than the conventional monitoring timer circuit 50,
A time-up signal is output each time a no-signal state is detected. The number of outputs is counted by the counter 52,
The permission signal for performing time-up for a certain number of times or more is stopped. The logical sum of both time-up signals is obtained by the OR circuit 53 and sent to the neighbor station status confirmation frame sending circuit to become a start signal for sending the neighbor station status confirmation frame. As described above, once a no-signal state is detected, a plurality of neighboring station state confirmation frames are transmitted in a short period of time, and the state of the transmission path can be confirmed reliably and in a short period of time.

(5) Parameter setting from external device The loop type transmission device is connected to the external device 3 via the device interface unit 6. The data processing unit 4 of the node 2 periodically stores the number of normal reception frames and the number of abnormal reception frames of both transmission path systems, and the number of times of disconnection / restoration of the node at a specific address of the dual port memory 62. Thus, the external device 3 can monitor the current line state of the node.

Conversely, the monitoring cycle and threshold of the received frame and the monitoring cycle and threshold of the number of times of disconnection / return can be set for the node using the dual port memory 62 and the interrupt circuit 61. This enables settings according to the system.

(Effects of the Embodiment) According to the above-described first embodiment, it is possible to change the condition of restoration in accordance with the unstable state of the transmission system, without repeating disconnection and restoration unnecessarily. The system can be stabilized.

When a no-signal state is detected, the state of the system can be surely and quickly confirmed and started. Further, the conditions can be changed according to the system. (Modification) In the above-described embodiment, the condition for restoration is the number of received frames in which an abnormality occurs at least once in the state at the time of disconnection. However, as a method for determining this condition, arithmetic mean or variance is used. Is also possible.

[0047]

According to the present invention, when disconnection is performed at the frequency of occurrence of an abnormality, the bias of failure occurrence is determined, and a recovery condition is set in accordance therewith, whereby the disconnection / recovery operation is repeated and the communication state becomes unstable. Thus, it is possible to provide a loop-type transmission apparatus that can prevent the loop-type transmission from converging and converging to a stable state.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a first embodiment of a loop transmission device of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of a transmission station (transmission node) in FIG. 1;

FIG. 3 is a block diagram showing a detailed configuration of a recovery counter of FIG. 2;

FIG. 4 is a block diagram illustrating a schematic configuration of a no-signal detection circuit included in the loop control circuit of FIG. 2;

[Explanation of symbols]

 1a, 1b: Transmission path 2a-2n: Node (transmission station) 3, 3a-3n: External equipment 4: Data processing unit 41: CPU 42: Memory 5: Internal bus 6: Equipment interface unit 61: Interrupt circuit 62: Dual port memory 7 ... Media access control circuit 8 ... Loop control circuit 9 ... Detection counter 10 ... Transceiving circuit 20 ... Recovery counter 200 ... Response frame check circuit 201 ... Counter 202 ... Register 203 ... Comparison circuit

Claims (5)

[Claims] 1. A plurality of nodes capable of transmitting and receiving data in both directions and repeating data in a direction opposite to a side on which data is received are transmitted through a plurality of nodes.
A cascade connection is formed in a pair of transmission lines in a ring, at least one of the plurality of nodes is always prohibited from being repeated, and a terminal station notification frame for notifying a transmission path abnormality from another node is received. When a repeat node is started, and when a recovery notification frame notifying the recovery of the transmission path from another node is received, a reset frame is sent out, all nodes in the system are initialized, and the end node itself returns to the repeat state. A loop-type transmission apparatus configured to detect a fixed abnormality between neighboring stations in a response frame from the neighboring station to a neighboring station status confirmation frame issued by the node at the time of transmitting the own station or detecting no signal. Abnormality detecting means, counting the number of abnormal frames of frames received by the node during a predetermined time, and detecting abnormal frames during the predetermined time. A second abnormality detecting means for detecting that there is an abnormality between neighboring stations when the value exceeds a threshold value, and observing an abnormality occurring within a divided time obtained by further dividing the monitoring time of the transmission frame into a plurality. 3. A loop transmission device comprising: third detection means for detecting a bias in occurrence of abnormality. 2. The method according to claim 1, wherein the third detecting unit changes the recovery condition of the abnormal part according to the reason for determining the separation of the abnormal part. When the number of frames exceeds the threshold value, recovery detection is determined to be continuous when recovery detection continues normally for a certain number of times in accordance with the frequency of occurrence of abnormalities and its bias, thereby preventing the repeated state of the disconnection recovery operation from continuing. 2. The loop type transmission device according to claim 1, wherein 3. A method of counting the number of times of disconnection and recovery, monitoring whether the disconnection and recovery operations are repeatedly performed within a predetermined time, and, if the number of times of disconnection and recovery continues more than a predetermined number of times, the side of the side that repeats abnormality and recovery 3. The system according to claim 2, wherein the recovery processing is completely stopped to stabilize the system.
A loop-type transmission device as described in the above. 4. The loop transmission apparatus according to claim 1, wherein upon detecting the no-signal, a plurality of frames of the inter-station state confirmation frame are transmitted in a short time to check the line state immediately. 5. An upper-level external device connected to each of the nodes can read a cause of disconnection, a count value of an abnormal frame and a normal frame to be received, and the number of times of disconnection / recovery, and furthermore, a threshold value of a reception abnormal frame. 2. The loop transmission apparatus according to claim 1, wherein a detection time interval, a threshold value of a disconnection / recovery count, and a monitoring time thereof can be set.