JPH0353636A - Method of controlling communication between master and slave - Google Patents

Abstract

PURPOSE:To easily attain the processing at the time of abnormal transmission by applying the monitor of the operating state of a slave with a master and the stop control to a controlled equipment by the slave. CONSTITUTION:A master 1 in fully responsible to the transmission controls the slave 2 and devices such as a solenoid and a motor connected to the succeeding branch via a communication line 3. The master 1 always monitors the data returned from the slave 2 and sends a signal with a prescribed level sent normally from the master 1 to the slave 2 as the signal of a different level therefrom when the abnormality is detected, thereby allowing the slave 2 to receive the signal and to stop the timer control and the counter control of output equipments. Thus, the processing at the time of abnormal transmission is facilitated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to master-slave communication in which a master and a plurality of slaves are connected through a communication interface, and data is cyclically exchanged between the master and the plurality of slaves. This paper relates to control methods, especially master-slave communication control methods that can handle transmission abnormalities. [Prior Art] A system is known in which a master and a plurality of slaves are connected via a communication interface and various controlled devices including motors and solenoids connected to each slave are remotely controlled.

By the way, if a transmission abnormality occurs in such a system, it is necessary to stop timer control and counter control of various controlled devices such as motors and solenoids connected to each slave. For this reason, conventionally, the slave is controlled by, for example, i) adding a program that sends back the current operating state of the slave side to the master side; ii) adding a program that sends back a cancel command from the master side.

[Problem to be solved by the invention]

However, although this increases the reliability of the device itself, the problem arises that the program structure of the entire device becomes complicated and the time required for transmission increases. In addition, since it is necessary to add programs, it becomes necessary to use a microcomputer that is more expensive than the one currently used, which not only increases costs but also increases the size of the system. There is a problem.

[Means to solve the problem]

The master 2 and multiple slaves are connected through a communication interface, and data is exchanged cyclically between the master 2 and the multiple slaves, while the slaves read input signals from human-powered devices and transmit their status data to the master. , timer control of the output device according to the data received from the master. In a master-slave communication control method that performs counter control, the master constantly monitors the data returned from the slave, and when an abnormality is detected, the signal of a predetermined level that is normally transmitted from the master to the slave is changed to a different level. It is transmitted as a signal, and when the slave receives the signal, the timer control and counter control of the output device is stopped.

[Effect]

The master constantly monitors the data sent back from the slave,
When an abnormality is detected, the master sends a signal at a predetermined level that is normally sent to the slave 2 as a signal at a different level, and the slave receives the signal and controls the timer and counter of the output device. To make it possible to cancel control and facilitate processing in the event of transmission abnormality.

Embodiment] FIG. 1 is a block diagram showing an example of a system configuration to which the present invention is applied. In the figure, ``■'' is a master having full responsibility for transmission, and controls the slave 2 and the solenoid, motor, etc. connected to the slave 2 via the communication path 3. As the communication path 3, a serial communication path is generally used to save labor, but a parallel communication path may also be used.

FIG. 2 shows an example of the slave structure. The slave 2 is connected to the communication path 3 via a communication interface 22 in order to communicate with the master.

The address setting circuit 23 is for setting the communication address of the slave. This address is also registered in advance on the master side, and the master specifies a plurality of slaves using this address and performs communication.

The CPU 2 1 controls the entire slave 2, and uses a one-chip microcomputer or the like. 24 is an input/output control interface that controls the interface with human output equipment.

FIG. 3 shows an example of formatting data sent and received between the master and slave, taking the 16 point as an example.

Identification code C indicates the type of data (human output (i/o
) data, timer settings, etc.), and address A is assigned to multiple slaves and is used to identify each slave.

Since the communication formant is a fixed length for transmission, here it is assumed that 16 boats are used regardless of the input/output specification, and the input/output (I/O) structure of the boat or the jumper wiring of the slave (see Figure 2) is used for transmission. (see reference numeral 25). Furthermore, it is assumed that I/O data is basically transmitted cyclically. In the transmission format from the master to the slave, those designated as output ports are designated as ON (“l”) or OFF (“0”), and those designated as manual ports are designated as ON (“l”) or OFF (“0”). All are set to "0". On the other hand, in the slave-to-master transmission format, the input port is set to the latest read state, and the output port is sent to the current state. The transmission is also performed with a fixed length of 16 ports. Therefore, even if the output port is specified, the master can grasp the current state of the slave.

In the format example shown in FIG. 3, port 1-A. ~A, is the output, and A8 to A15 are the input designations. Figure (a) shows data from the master to the slave, here A. ，
This is an example in which AIl A4 is ON and the others are OFF. Note that those designated as input ports are designated as "0". Figure (b) shows data from the slave to the master.
Here, A. ,A. . ,A
In this example, 41 is ON and the others are OFF. Also, the current status is set to the port specified for output.

In this way, even if the port is designated as an output, the current state of the slave can be constantly monitored by the data returned from the slave to the master without any new transmission communication. Therefore, data from the master to the slave, including data during timer control and counter control, is set as a "high (H) signal," and when an abnormality is detected as a result of monitoring, the data from the master to the slave is sent as a "high" signal. If the signal is changed from "H" to "low (L)", the slave can receive the signal and cancel timer control and counter control.

FIG. 4 is a flowchart showing the operation of the master, and FIG. 5 is a flowchart showing the operation of the slave.

The operation of the master will be explained with reference to FIG.

After transmitting data, the master determines whether or not data has been received from the slave (see ■, ■Reference).

On the other hand, when specifying output data, it is determined whether the output data from the master matches the status of the received output device, and if they do not match (abnormal), the output is forcibly turned off from the master side. and performs error processing (see ■.■, ■). The above operation is repeated for 16 ports, and after checking the end, data is sent to the slave (see ■, @l).

The operation of the slave will be explained with reference to FIG.

First, determine whether data has been received from the master (■
), if data is received and it is specified as an output port (see ■, ■), the “H” - “L” of the received data
” is detected, and if the change is confirmed, it is checked whether the timer and counter are operating (see ■ and ■).

And a timer. If the counter is in operation, stop it (see ■). Output data of more than 16
Repeat for each port (see ■), and after completing the data check, send the current output state to the master (see ■ to 0).

〔Effect of the invention〕

According to this invention, the master receives and monitors the return signal from the slave, and when it detects a transmission abnormality, it transmits a signal indicating that. This provides the advantage of being able to easily perform abort control on controlled equipment.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a system configuration to which the present invention is applied, FIG. 2 is a block diagram showing an example of a slave configuration, and FIG. 3 is a block diagram showing an example of formatting data sent and received between a master and a slave. 4 is a flowchart for explaining the operation of the master, and FIG. 5 is a flowchart for explaining the operation of the slave. Code explanation 1...Master, 2 (2A to 2C)...Slave,
3... Communication path, 21... CPU, 22... Communication interface, 23... Address setting circuit, 24...
・Input/output control interface, 25...Jumper wiring.

Claims (1)

[Claims] 1) A master and a plurality of slaves are connected through a communication interface to cyclically exchange data between the master and the plurality of slaves, and the slave reads input signals from input devices and transmits status data thereof. In the master-slave communication control method, the master constantly monitors the data returned from the slave, and controls the timer and counter of the output device according to the data received from the master.
When an abnormality is detected, the master sends a signal at a predetermined level that is normally sent to the slave as a signal at a different level, and when the slave receives that signal, it stops the timer control and counter control of the output device. A master-slave communication control method characterized by: