JPH11355331A - Data communication control method for remote measurement system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a CPU at a master station side to relieve a load required for communication control processing without the need for the master station to make polling communication with all slave stations at all times. SOLUTION: A polling message sent from a master station 3 circulates through all slave stations 1-1-1-5. The slave station 1-1 sends a transmission request of a data message to the other stations and once transmits a polling acknowledgement to the master station 3 when the slave station 1-1 receives the polling message. The master station 3 sends the polling message to the slave station 1-2 that is next to the slave station 1-1 having sent the polling acknowledgement just before to restart the polling. After the polling message circulates through the slave stations for a predetermined number of times, the master station 3 allows the slave stations to make the polling acknowledgement forcibly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a remote measurement system that collects measurement data from a plurality of measurement stations scattered in a distance and displays and monitors the measurement data at one monitoring station.
In particular, it relates to a communication control method of the measurement data.

[0002]

2. Description of the Related Art Data measured at a plurality of measuring stations (hereinafter, referred to as slave stations) scattered at a distance are collected and displayed by one monitoring station (hereinafter, referred to as master station) via a serial communication line. In a remote measurement system, a master station and each slave station generally communicate by polling / selecting. The outline of the polling / selecting communication will be described with reference to the drawings.

As shown in FIG. 1, a master station normally performs polling communication with each slave station connected in a multi-drop manner, and determines whether there is data to be transmitted from the slave station to the master station. Sends a polling message inquiring about. The slave station having the data to be transmitted sends the data to the master station at the timing when the polling message is sent to its own station.

On the other hand, when it is desired to perform communication from the master station to an arbitrary slave station, the polling communication is temporarily interrupted at that time, and a selecting code is embedded in order to identify the master station to be the destination. Send a message. The message in which the selecting code is embedded circulates through each slave station, and only the slave station that matches the selecting code recognizes this data and responds as to whether or not reception is possible.

As described above, by performing centralized monitoring and control by polling / selecting in which only the master station manages communication lines, it is possible to easily cope with an increase or decrease in the number of slave stations in the multi-drop format.

[0006]

However, in the above-mentioned centralized monitoring and control method using the polling / selecting method, polling must be performed for all slave stations to which the master station is always connected. Most of the CPU operation of the master station is devoted to this processing.
There has been a problem that the load on the CPU is increased.

As a method used to solve such a problem, for example, a method disclosed in Japanese Patent Application Laid-Open No. 5-300156, entitled "Method of Communication Between Multiple Terminal Devices" can be mentioned. Hereinafter, this content will be briefly described.

In communication between a master station and a plurality of slave stations, (1)
In a steady communication state for controlling the work machine, communication is performed by a polling method. (2) When a specific terminal device is connected to a slave station, and when a control program of the work machine is changed, communication is performed by a token pass method. I do. These two different communication systems are controlled so as to check the processing state of the master station in advance, and to switch to the polling system if the arithmetic processing for controlling the work machine is being performed and to the token pass system if the arithmetic processing is not being performed. .

In the polling communication, the master station transmits input / output data sequentially to the first to nth slave stations connected to the subordinate station, and the slave station receiving the data transmits the input / output data to the master station. Send to. Each slave station cannot transmit data to the master station except when receiving data from the master station.

[0010] In the token path communication, a communication path between a master station and a plurality of slave stations is previously set in a ring shape, and the master station and the slave stations can transmit data when a signal called a token is received. When the communication is completed, the token is sent to the next station (the master station or the slave station), and the communication is sequentially performed on the circular route.

However, Japanese Patent Laid-Open Publication No. Hei.
In order to apply the technology described in Japanese Patent Application Publication No. 6 (1994), both the master station and all slave stations need to control programs for both the polling communication system and the token pass communication system and the state of the master station for performing switching control between them. It must have a means for monitoring, which causes a new problem that the configuration and the control method become complicated.

[0012] The polling central control communication method of the present invention comprises:
It is an object of the present invention to minimize the control that the master station always performs polling communication with respect to all slave stations, and reduce the load required for the CPU of the master station for the communication control process.

Further, the polling central control communication method of the present invention aims to realize the above-mentioned effect with a simpler configuration without installing two different communication programs (polling communication and token path communication). I do.

[0014]

In order to achieve the above object, a data communication control method for a remote measurement system according to the present invention provides a method in which one monitoring station collectively receives data measured by a plurality of measurement stations. In the data communication control method of the monitoring system, the polling message sent by the monitoring station is sent to the first measuring station in a predetermined order, and the plurality of measuring stations receive the polling message. At this point, it is determined whether or not it has data to be sent to the monitoring station or another measurement station, and if it does not have the data to be sent, the polling message is sent to the next measurement station. If it has, the destination is determined, and if the destination is the monitoring station, a polling response message is added to the monitoring station and transmitted, and if the destination is the another measuring station,
After transmitting only the data to be transmitted, the polling response message is transmitted to the monitoring station, and the monitoring station receiving the polling message transmits the polling response message in the predetermined order. A polling message is sent again to the next measuring station, and when the polling message goes through all the measuring stations, processing is performed so that a polling response message addressed to the monitoring station is sent from the last measuring station. Features.

Further, in the data communication control method for a remote measurement system according to the present invention, in addition to the above configuration, the number of times of the polling message is set arbitrarily, and the polling message circulates around all the measuring stations by the number of times. When it detects that
It is characterized in that processing is performed so that a polling response message addressed to the monitoring station is forcibly transmitted from the last measuring station.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an apparatus adopting the polling centralized control communication method according to the present embodiment. It should be noted that there is no particular change in the device configuration itself in both the present invention and the prior art.

As shown in the figure, a plurality of (five in the embodiment) slave stations 1-1 to 1-5 and one master station 3 are
They are connected by a communication path 2 which is a serial communication line. The measurement data measured in each of the slave stations 1-1 to 1-5 is transmitted to the master station 3 via the communication path 2.

The master station 3 receiving the information centrally monitors and manages the slave stations based on the measurement data sent thereto.

Each of the slave stations 1-1 to 1-5 is connected to a master station 3 described later.
In accordance with the instruction from, measurement is performed at regular time intervals, and measurement data obtained thereby is sent to the master station 3.

The master station 3 collects and records measurement data sent from the slave stations 1-1 to 1-5 at regular intervals, and records the measurement data in a predetermined format recognizable by an operator operating the master station 3. Display by

The master station 3 is connected to each slave station 1- 1 by the operator.
Operation instructions (measurement start instruction, measurement end instruction) to 1 to 1-5 are notified via the communication path 2.

The measurement data is collected by the master station 3 by each slave station 1-.
For 1 to 1-5, polling communication is performed. Each of the slave stations 1-1 to 1-5 receiving this monitors the monitored objects under its own control in accordance with the instruction. Then, the prepared slave station sequentially transmits the measurement data to the master station 3 according to the polling timing.

FIG. 3 is a time chart showing, in chronological order, communication between the master station 3 and each of the slave stations 1-1 to 1-5 by the polling communication method according to the present embodiment. In the steady state, the master station 3 always performs a polling operation for each slave station. The polling message used for this polling operation circulates through the slave stations in a predetermined order, for example, a token (transmission right) of a token pass system. The polling message is always generated by the master station 3.

The polling message sent from the master station 3 is
The slave stations 1-1 → 1-2 → 1-3 →... → 1-5 are sequentially visited, and after all the slave stations have been visited, the last slave station 1−1 is completed.
5 is returned to the master station 3, and the polling operation completes.

Subsequently, the slave station 1-1 sends the polling message to the master station 3 or other slave stations 1-2 to 1-5 at the timing of receiving the polling message in the polling operation described above.
Sends a transmission request for a data message other than the polling message. Note that each of the slave stations 1-1 to 1-5 cannot transmit a message at a timing other than the timing at which the local station itself receives the polling message.

Slave station 1 that has finished sending a data message transmission request
1 temporarily sends a polling response to the master station 3 and returns the transmission authority. When a data message request is sent to the master station 3, the transmission authority is returned by the polling response by adding the information at the time of the polling response.

When the transmission authority is returned by the polling response, the master station 3 sends the data message to be transmitted to each slave station, if any. Then, the master station 3 sends a polling message to the slave station 1-2 next to the slave station 1-1 which has just sent the polling response, and restarts the polling operation.

The slave station 1-2, which has received the polling message from the master station 3, changes the other slave stations 1-1 and 1-3-1 at that time.
For -5, if there is no data message transmission request other than the polling message, the polling message is transmitted to the next slave station (in this case, slave station 1-3) in a predetermined order.

If there is no data message transmission request in all of the slave stations 1-1 to 1-5, the polling message is not returned to the master station 3 until it returns once. During this time, even the master station 3 loses any transmission authority, similarly to the slave stations 1-1 to 1-5. In this case, from the master station 3 to each slave station 1-
Asynchronous other than polling communication toward
Unexpected communication cannot be performed.

In order to prevent such a situation, the number of polling rounds is counted, and when a predetermined number of polling messages are cycled between the stations, the master station 3 is forcibly made a polling response. In the example shown in FIG.
After the polling message is circulated three times, the master station 3 is once made to perform a polling response.

Next, a polling message (polling response message) used in the communication method according to the present embodiment will be described with reference to FIG. The information constituting this polling message is an essential element for realizing the communication method of the present invention.

The next station number 41 is a destination (slave station 1-1 to 1-5) to which a polling message (polling response message) is to be delivered next.
Alternatively, it indicates the station number of the parent station 3).

The originating station number 42 indicates the station number of the source (slave station 1-1 to 1-5 or master station 3) of the polling message (polling response message).

The current number of rounds 43 indicates the number of remaining rounds for polling to force the master station 3 to make a polling response.

FIG. 5 is a flowchart showing the processing of the polling communication control program executed by the master station 3 to realize the communication method of the present embodiment.

When the program is started to be executed, whether or not a polling operation is currently being performed (whether or not a polling message exists)
It is checked whether or not it is (step 5-1). Since this polling message is generated only by the master station 3, the polling message does not exist immediately after the start of the program execution, and the polling operation cannot be performed at this point.

Thereafter, the master station 3 sets the next station number 41 to "1" which is the station number of "slave station 1-1", the calling station number to "0" which is its own station number, and the current station number. An arbitrary number of tours (for example, "3" for three times) is set as the number of tours (step 5).
-8) Generate and transmit the first polling message and start the polling operation (step 5-9).

After transmitting the polling message, the master station 3 transitions to a state of waiting for the reception of the polling message or polling response message returned from each slave station (step 5-).
2).

When either the polling message or the polling response message is received, the master station 3 determines whether the received message has returned after making a round around each slave station or has been returned during the round. It is determined whether or not there is (step 5-
3).

If the received message has returned after making a round of each slave station, it is first checked whether or not there is a data message to be transmitted at that time (step 5-4). If there is, it is transmitted (step 5-5),
If there is no corresponding data message, a polling message having the same setting as in step 5-8 is transmitted to the first slave station 1-1 in a predetermined polling order. After the transmission of the polling message, the state shifts to the polling reception waiting state again.

When the received message is returned during the tour, it is first checked whether there is a data message to be transmitted at that time (step 5-6). The process is performed (step 5-7), and if there is no corresponding data message, the process proceeds to a polling message setting process. However, in this case, in the next station number 41, the station number of the next station of the slave station that returned the polling message to the master station 3 during the tour, for example, if the slave station 1-3 returned the polling message, The station number "4" of the slave station 1-4 is set (step 5-10), and this new polling message is transmitted (step 5-11). After the transmission of the polling message, the process shifts to a polling reception waiting state as in the case of one round.

FIG. 6 is a flowchart showing the processing of the polling communication control program executed by each slave station in order to realize the communication method of this embodiment.

When the execution of the program is started, each slave station immediately enters a polling reception waiting state (step 6).
1). In this state, each slave station stands by without performing any other communication until each slave station receives a polling message to its own station.

Here, it is assumed that the master station 3 sends a polling message to the slave station 1-1. At this time, the slave station 1
1 confirms whether there is a data message to be transmitted in its own station (step 6-2), and if a data message exists, determines whether or not this is a data transmission to the master station 3 (s).
step 6-5).

If the data message is for the master station 3, a polling response message (the next station number is "0", the calling station number is "1", and the current number of rounds is "3") is added. Then, the data transmission and polling response transmission to the master station are transmitted together (step 6-7).

In step 6-5, if the data message is for a device other than the master station 3, only the data message is sent to the corresponding party, for example, to the slave station 1-2 (step 6). -6). When transmission is completed, master station 3
Then, a polling message in which the next station number 41 is set to "2", the calling station number 42 is set to "1", and the current round number 43 is set to "3" (step 6-11), and the program returns to the top of the program. The state shifts to the polling reception waiting state again.

In step 6-2, if there is no data message to be sent, 1 is subtracted from the "current number of tours" in the sent polling message (step 6-2).
3), it is determined whether the value has become 0 (ste)
p6-4). If it is not 0, the content of this polling message is set to the next station number 41 as "1 plus 1 (= 2)",
The source station number 42 is changed to "1", and the current number of tours 43 is changed to "3 minus 1 (= 2)" (step 6-8), and transmitted to the slave station 1-2 which is the next station, (step 6-9). ), And shift to a polling reception waiting state.

In step 6-4, when the current number of tours 43 becomes 0, as described above, the process shifts to step 6-10 in order to forcibly cause the master station 3 to temporarily perform a polling response.

[0050]

As described above, according to the polling centralized control communication method of the present invention, the process of imitating the token of the token pass communication is partially incorporated into the basic polling communication processing control, thereby enabling the parent polling communication. There is no need for the station to constantly perform polling communication for all slave stations,
It becomes possible to reduce the load required for the CPU on the master station side for the communication control processing.

Further, according to the polling centralized control communication method of the present invention, the above effects can be realized with a simpler configuration without installing two different communication programs (polling communication and token path communication). it can.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a measurement system to which a communication method according to an embodiment of the present invention is applied.

FIG. 2 is a time chart illustrating communication between a master station and a slave station in the communication method according to the embodiment of the present invention.

FIG. 3 is a time chart showing a forcible polling response to a master station. .

FIG. 4 is a diagram showing a format of a polling message / polling response message.

FIG. 5 is a control flowchart showing communication processing on the master station side.

FIG. 6 is a control flowchart showing communication processing on the slave station side.

FIG. 7 is a time chart showing communication between a master station and a slave station in the related art.

[Explanation of symbols]

 1-1 to 1-n slave station 2 communication path 3 master station 41 next station number 42 originating station number 43 current round number

Claims (3)

[Claims] 1. A data communication control method for a monitoring system in which one monitoring station collectively receives and monitors data measured by a plurality of measuring stations, wherein a polling message transmitted by the monitoring station is determined in advance. Send to the measurement station at the beginning of the order, the plurality of measurement stations, at the time of receiving the polling message, whether or not it has data to be sent to the monitoring station or another measurement station Judgment, if it does not have the data to be sent, send the polling message to the next measurement station, if it has, judge its destination, if the destination is the monitoring station, A polling response message is added and transmitted, and if the destination is the another measurement station, the polling response message is transmitted to the monitoring station after transmitting only the data to be transmitted,
The monitoring station that has received the polling message sends a new polling message to the next measuring station after the measuring station that sent the polling response message in the predetermined order, and the polling message sends all the measuring stations one by one. A data communication control method for a remote measurement system, wherein a polling response message addressed to the monitoring station is sent from the last measurement station when the communication has been performed. 2. A method of arbitrarily setting the number of rounds of the polling message, and when detecting that the polling message has circulated all the measuring stations by the number of rounds, polling from the last measuring station to the monitoring station. 2. The data communication control method for a remote measurement system according to claim 1, wherein a response message is forcibly transmitted. 3. The data communication control method for a remote measurement system according to claim 1, wherein the plurality of measurement stations are connected to the monitoring station in a multi-drop manner via a serial line. .