JPH0983557A - Looped transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a looped transmission device which can realize statistical line control in addition to line control when disturbance enters a line. SOLUTION: In the looped transmission device connecting plural transmission stations 2 by a duplex looped transmission line, the respective transmission stations 2 are provided with data processing parts 4 executing the processing of transmission/reception data, unit interface parts 6 connected to external units 3, media access control parts 7 controlling access to transmission mediums, loop control circuits 8 controlling the loop lines and transmission/reception circuits 10 converting a logic signal and a transmission signal. Counters 9 counting the number of times for the normality/abnormality of transmission frames received within a prescribed time independently of the loop control circuits 8, comparing both number of times and statistically controlling the lines is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loop type transmission of a double loop transmission line of a transmission device used for data transmission between various devices constituting a supervisory control system of steel plant and other various industrial plant facilities. Regarding the device.

[0002]

2. Description of the Related Art There are various types of transmission line configurations (topologies) of transmission devices used in steel plants and other industrial plants, and they are roughly classified into the following three types. Each of these has its own characteristics, and at present, they are used properly depending on the application system. Of these, the following is a comparison from the redundancy against the transmission line failure, the system scale, the communication form, etc.

[0003]

[Table 1]

As can be seen from the above table, redundancy against transmission line failure Star>Loop> Bus system scale Loop>Bus> Star Communication mode Loop bus> Star Buses and stars are used in the branch line system, and in the trunk line system. Loop is suitable.

However, in the case of a loop type transmission device, the other two
However, it is more complicated because it is necessary to control the loop line itself. The transmission station of normal loop transmission needs to monitor the communication state with the adjacent station and disconnect the portion when an abnormality is detected. In addition, there is usually a line control station that controls the loop line, and the line control of the entire system is usually performed.

[0006]

As described above, the loop transmission device usually has an abnormality detection and disconnection control function. However, the method is intended for a fixed failure mode, and cannot sufficiently control a failure mode in which an unstable state continues or a low frequency failure.

For example, in some systems, system disturbance due to infrequent failures may cause a problem in control responsiveness, and it is necessary to separate such failure points. On the other hand, due to application restrictions, it may be more stable systematically if the system does not operate even if a temporary abnormality occurs, and the requirements vary depending on the application system.

Further, an abnormality may occur during line control in the event of an abnormality, and line control different from the actual failure state may be performed.

The present invention has been made on the basis of such a situation, and it is possible to judge whether the failure is a fixed one or a sporadic one, and to recognize the occurrence frequency even in the case of a sporadic one.
In addition, even if disturbance occurs in the line control when a disturbance occurs and an abnormal state occurs, the system can be corrected again, and a loop type transmission device that enables loop line control according to the system is provided. The purpose is to do.

[0010]

In order to achieve the above object, the present invention is configured as follows.

The invention according to claim 1 is a loop type transmission apparatus in which a plurality of transmission stations are connected by a double loop transmission line, wherein each transmission station includes a data processing unit for processing transmission / reception data, A device interface unit for connecting to an external device, a media access control unit for controlling access to a transmission medium, a loop control circuit for controlling a loop line, and a transmission / reception circuit for converting a signal between a logic signal and a transmission signal. And a counter for counting the normal / abnormal number of transmission frames received within a fixed time and comparing the two to perform statistical line control independently of the loop control circuit. It is a loop type transmission device.

According to the first aspect of the invention, by comparing the counts of normal / abnormal transmission within a certain period of time, it is possible to determine whether the fault is a fixed fault or a sporadic fault, and further a sporadic fault. Even in the case of, the occurrence frequency can be recognized. For example, if there is no normal transmission count and only the abnormal transmission count is incremented, it is determined that a permanent failure has occurred and the abnormal portion is separated. When detecting abnormalities sporadically, set a threshold value for the number of abnormalities that occur within a certain time.If an abnormality is detected with an occurrence frequency exceeding this value, disconnection is executed and ignored if it is less than that. To do.

The invention corresponding to claim 2 is the loop type transmission device according to claim 1, wherein each of the transmission stations transmits at a constant period, and the transmission station of its own is included in the header portion of a normal data frame. The loop type transmission apparatus is characterized by including means for performing loop control by adding a mode for loop control, transmitting information periodically, and collecting the information by a loop circuit control station.

The invention according to claim 2 is effective in the case where each transmission station transmits at a constant period. Each transmission station stores its loop control mode in the transmission frame header of this fixed period transmission and transmits it. The loop line control station in the loop system collects this information and creates a map of each transmission station, and resets the system in a state where control is impossible or in response to a system initialization request from each transmission station. This makes it possible to correct the system again, even if a disturbance occurs in the line control when a disturbance occurs and an abnormal state occurs.

The invention corresponding to claim 3 is that, in the loop type transmission device according to claim 2, the collected information can be referred to by an external device to be connected, and the mode can be controlled from the external device. A loop-type transmission device comprising means.

According to the third aspect of the present invention, the statistical information can be referred to from an external device through a device interface, so that the external device can designate system reset and disconnection of an abnormal portion. .

According to the invention corresponding to claim 3, the information according to claim 2 can be referred to the external device through the device interface, and the loop control state of the transmission station can be fixed from the external device. enable. This fixed state can be released only from the requested external device. This enables loop line control according to the system.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> (Structure) FIG. 1 shows an example of a transmission system according to the present invention. This transmission system is a double loop transmission line 1-
1, 1-2, a plurality of transmission stations (STN) 2 ₁ , 2 ₂ ,
2 _3, 2 ₄ ... 2 _n are connected in a distributed, further each of the 2 ₁ to 2 _n of these transmission stations PLC (programmable logic controller), a computer, a personal computer, I / O devices, and other control devices of the external It is connected as the device 3.

As shown in FIG. 2, each of the above-mentioned transmission stations 2 ₁ to 2 _n has a data processing unit 4 for performing transmission / reception data processing, a device interface unit 6 for connecting to an external device 3, and an access control for a transmission medium. It is composed of a media access control unit (MAC) 7 for performing the above, a loop control unit (LP) 8 for controlling the loop line, and a transmission / reception circuit 10 for converting a logic signal and a transmission signal. A counter that counts the number of normal and abnormal communication with the neighboring station is provided, and the communication state with the neighboring station is determined by statistically checking the counter value at a sufficient time interval that can ignore transient time. It is a thing.

The above-mentioned transmission stations 2 ₁ to 2 _n are constructed as shown in FIG.

Each transmission station 2 includes a CPU 41 including a peripheral circuit for performing transmission / reception data processing and line control processing, and this CP
A data processing unit 4 connected to an internal bus 5 derived from U41 and including a ROM 42 for storing operation programs and other necessary programs and a RAM 42 for temporarily storing processing data, and an external device Bus 1
3 and the internal bus 5, and an interrupt circuit 61 for outputting interrupt signals 14 and 16 to an external device and the CPU 41,
Similarly, a device interface unit 6 which is connected to the bus 13 from the external device 3 and the internal bus 5 and which is accessible from both the external device 3 and the CPU 41 and a device interface unit 6 which is connected to the internal bus 5 is used for transmission / reception. Media access control circuit (MAC) 7 for controlling timing
Similarly, it is connected to the internal bus 5 and monitors / controls the communication state with the adjacent station and selects the reception frame from both sides to select the MAC.
Loop control unit (LP) 8 for performing loop control for sending to 7
And a transmission / reception circuit 10 for converting a signal level on a transmission line having a double loop configuration with a logic signal, and a detection counter for detecting the number of abnormalities by monitoring the reception signals of both systems passed from the transmission / reception circuit 10 to LP8. It consists of (CNT) 9.

Since the application for the LP8 system has already been filed (Japanese Patent Application No. 7-53017), its explanation is omitted.

The above-mentioned detection counter 9 is independently provided in each of the transmission lines 1-1 and 1-2 which are in the dual system, and counts the normal reception frame number and the abnormal reception frame number, respectively. Further, regarding the abnormal frame, the CRC error and the short frame (shorter than the minimum frame configuration) are counted according to the detection factor.

(Operation) First, a basic method of loop control of this transmission device will be described below.

The transmission system includes a line control station for controlling the whole line and a normal station. However, the hardware has the configuration shown in FIG. 2 for both, and there is no difference. Also, there is no difference in normal transmission, and the difference lies in the line control operation at the time of abnormality.

(1) At the time of normal transmission When the transmission request is generated by the data processing unit 4, the transmission station 2 creates a data frame and sends the data to the MAC 7 at the transmission timing determined by the MAC 7. MAC
7 further sends this data to LP8, which is a dual transmission line 1 in which signals flow in opposite directions.
-1 and 1-2.

The receiving side receives data from the two transmission lines 1-1 and 1-2, and the LP8 outputs the received frame from the MAC 7 to the data processing unit 4 on a first-come-first-served basis. The data processing unit 4 discriminates this frame, stores it in the memory 42, and executes the receiving process.

(2) When an abnormality is detected LP8 returns a response code when a frame is received from a neighboring station. The transmitting LP 8 monitors the response from the adjacent station, and if no response is returned, determines that the adjacent station is abnormal and issues an interrupt to the data processing unit 4 to notify it. This allows CP
U41 prohibits transmission / reception on the abnormal side of the transmission station 2 to be a terminal station,
In order to notify the line control station that it has become a terminal station, it is necessary to send a pattern signal called a terminal station code to the normal side.
Issue a command to 8.

Upon receiving this, the line control station prohibits the repeat of the signal until then, and changes from the state in which the circulation of the signal is prevented to the repeat permission.

(3) At the time of restoration When the abnormal portion is repaired to restore the normal state, the following procedure is performed.

At the transmission station 2 which has detected an abnormality and has become a terminal station,
The LP8 sends a confirmation code to the abnormal side at regular intervals. The LP 8 of the transmission station 2 which receives this returns a response code to this. When the LP8 of the transmission station that has transmitted the confirmation code returns this response code, it determines that communication with the adjacent station has been restored, and causes the CPU 41 to generate a restoration detection interrupt.

The CPU 41 issues a command to the LP 8 to send the recovery code to the line control station. The line control station that received the recovery code interrupts the CPU that the LP8 has received the recovery code, and the CPU 41 issues a command to the LP8 to send a reset code, initializes the system, and normalizes the transmission system. Restore the condition.

As described above, the loop line is controlled by LP8.
And the CPU 41 that controls it. However, such control has no problem if the abnormality is fixed, but it is difficult to deal with it when the abnormality is unstable.

Therefore, in the invention corresponding to claim 1, as shown in FIG.
It is provided between 0, and the frames received from the transmission paths 1-1 and 1-2 of both systems are independently checked and the number is counted.

The items to be counted are as follows.

(A) Number of normal frame receptions (b) Number of CRC error frame receptions (c) Number of short frame receptions The contents of this counter value are stored in the CPU 4 via the internal bus 5.
It can be read from 1.

From this value, the CPU 41 statistically determines the communication state with the adjacent station by the following procedure and controls the line.

<Judgment Method> (a) The CPU 41 reads this counter value at a constant cycle, and after reading, resets the contents of the counter 9.

(B) If the number of abnormal frame receptions continues to exceed the number of normal frame receptions over several cycles, it is determined that there is an unstable point on the line, and transmission / reception is prohibited on the abnormal side as in (2). And become a terminal.

The operation of this control software is represented by a flow chart in FIGS. 3 and 4. The same thing is carried out for the two transmission lines, but here, the case of the one transmission line will be described as a representative.

When the cycle in which the CPU 41 checks the contents of the counter 9 is T1, the transmission station 2 becomes a terminal station when the time abnormal frame of T1 × m exceeds the normal frame,
It is stable against transient disturbances and can handle cases where abnormalities occur continuously. Further, since the judgment is made by the sum of N pieces of data, the tendency can be accurately measured even if the transmission load varies, and the efficiency of the transmission system can be judged by comparing with the number of normal frames and abnormal frames.

In the invention corresponding to claim 2, when each transmission station 2 transmits its own frame, a mode for loop control is put in its frame header for transmission, and the line control station collects this and performs line control. Is to do.

As described above, the line control station performs line control by the dedicated code from the detected station when an abnormality occurs and when the abnormal station is restored. However, since this dedicated code is transmitted only when an abnormality occurs or is detected, if this code disappears due to a disturbance, the timing of line control will be lost until the next abnormality is detected.

In order to prevent this, each transmission station 2 puts the loop status code shown in FIG. 5 in the header of the transmission frame to be transmitted in a fixed cycle and transmits it.

Using the LP field of FIG. 5, each transmission station sends its loop control status.

When the line control station receives this frame and the state does not change for a certain period of time, the line control station determines that it is the state of the corresponding station.

When the transmission station in the system becomes a new terminal station, the line control station changes the signal repeat prohibition state to the permission state and permits the signal to circulate. If the recovery bit is set, a reset code is sent to return the transmission system to the initial state.

Next, the invention corresponding to claim 3 will be described. The above control was voluntarily performed by the transmission station. However, in this case, the control program can perform only fixed and general control, and cannot be modified for a special control system. The third aspect is to enable loop control from an external device (user) as well, so that the external device can issue a loop control request to the transmission station via the dual port memory.

Specifically, (1) The following loop status is provided on the dual port memory 62 so that it can be referred to by an external device.
(Refer to FIG. 6) (a) All transmission stations-Counter indicating the communication status with the neighboring station described in claim 1-Loop control status with the neighboring station (terminal station / normal status) (b) Line control station-above (A) -Loop control state of each transmission station 2 described in claim 2 (2) Request / response sequence between external device and transmission station The external device 3 makes a loop control request to the transmission station according to this sequence. The transmission station that has received the request returns a response after executing the processing. The external device and the transmission station use the interrupt circuit to notify the timing. The sequence in Figure 7,
The request / response format is shown in FIG.

The external device refers to the reception status of the 1-system and 2-system to confirm the communication status with the adjacent station. After confirming the frequency of occurrence of anomaly, formulating a permissible value in the applicable system, and when exceeding the permissible value, the terminal station status with the adjacent station (transmission / reception prohibited)
To

External equipment connected to the line control station is
In addition to this processing, monitor the station status of the entire transmission system, detect stations that frequently repeat the terminal status and normal status, and instruct the side that seems to have an abnormality to enter the terminal status. .

If this instruction is executed once, the transmission station holds the memory until a cancellation request comes.

(Effects) By implementing the present invention, reliable control can be performed by statistically determining an abnormality on a loop line as a temporary disturbance process as shown in the embodiment. Become. Further, even if the line control itself is not normally performed due to a disturbance, it is possible to make a timing that enables re-restoration.

Furthermore, since loop control can be performed from an external device, control according to the applicable system is possible.

<Modification> This embodiment has been described with respect to the loop control, but the method of statistically processing this abnormality can be applied to the bus type regardless of the topology. In that case, in the case of the present embodiment, the state is changed to the terminal station state, but it can be realized by leaving the system by the abnormality detection.

Further, in this embodiment, as the abnormal reception event,
Although the CRC error and the short frame are adopted, in addition to these, a frame format error, reception of a specific frame, a no-signal state, etc. can be added.

[0058]

According to the present invention, by using the means described in the above items 3 and 4, statistical line control can be performed in addition to line control at the time when disturbance occurs on the line.

It is possible to judge whether the failure is fixed or sporadic, and it is possible to recognize the frequency of occurrence even in the case of sporadic failures.
In addition, even if disturbance occurs in the line control when a disturbance occurs and an abnormal state occurs, the system can be corrected again, and a loop type transmission device that enables loop line control according to the system is provided. it can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a loop type transmission device which is an object of the present invention.

FIG. 2 is a block diagram showing a specific configuration of the transmission station of FIG.

FIG. 3 is a flowchart for explaining processing contents of a CPU 41 of FIG.

FIG. 4 is a flowchart for explaining processing contents of a CPU 41 of FIG.

5 is a diagram showing a transmission frame format of FIG.

FIG. 6 is a diagram showing a loop status.

FIG. 7 is a sequence for explaining the operation of the CPU 41 of FIG.

8 is a diagram showing the request / response format of FIG. 7. FIG.

[Explanation of symbols]

-1-1,1-2 ... transmission line, 2 ₁ to 2 _n ... transmission station, 3 ... external device, 4 ... data processing unit, 41 ... CPU, 42 ... memory, 5 ... internal bus, 6 ... apparatus interface unit, 61 ...
Interrupt circuit, 62 ... Dual port memory, 7 ... Media access control circuit, 8 ... Loop control unit, 9 ... Detection counter, 10 ... Transceiver circuit, 13 ... Bus, 14, 16 ... Interrupt signal.

Claims (3)

[Claims] 1. A loop-type transmission device in which a plurality of transmission stations are connected by a double-loop transmission path, wherein each of the transmission stations connects a data processing unit for processing transmission / reception data and an external device. A device interface section, a media access control section for controlling access to a transmission medium, a loop control circuit for controlling a loop line, a transmission / reception circuit for performing signal conversion between a logic signal and a transmission signal, and the loop control circuit Independently,
A loop type transmission apparatus comprising: a counter for counting the number of normal / abnormal transmission frames received within a fixed time period and comparing the two to perform statistical line control. 2. The loop type transmission device according to claim 1, wherein each of the transmission stations transmits at a constant cycle,
It is equipped with a means to put the mode for loop control of its own transmission station in the header part of a normal data frame and transmit information periodically, and the loop line control station aggregates this information and performs loop line control. Characteristic loop type transmission device. 3. The loop type transmission device according to claim 2, further comprising means for enabling the collected information to be referred to by an external device to which the information is connected and for enabling a mode control from the external device. Loop type transmission device.