JPH09128015A - Remote i/o system for plc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inform a master device of fault information without using a real I/O bit and to execute fault processing without giving burden to the master side. SOLUTION: When an excess current flows into an output of an external load with an I/O I/F part 21 or the like, a fault detection part 22 detects the excess current as a fault and outputs fault information. At the time of receiving the fault information from the detection part 22, a communication I/F circuit 23a stores the fault information in a management information storing area and transmits the information to the master device through a communication cable 5 to inform of the occurrence of the fault in a slave 2. At the time of receiving the fault information from the detection part 22, an output buffer 23b inputs the fault information as a buffer clear signal and clears output data received and latched from the master device through the circuit 23a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a remote master and a remote slave connected to the remote master via a communication cable. The remote master is notified of failure information generated on the remote slave side. Programmable controller (hereinafter "PLC")
That. ) Remote I / O system.

[0002]

2. Description of the Related Art In a PLC remote I / O system,
Conventionally, a failure that has occurred on the remote slave side has been notified to the remote master side as failure information.

For example, when a failure occurs in the remote output slave for OUT data, the failure information is given as another I
Remote input slave for N data or OUT / I
By connecting to the input of the remote input / output slave that can accept both N data, the other remote slave notifies the remote master as IN data.

Further, when a failure occurs in the remote input slave or the remote input / output slave, the remote master is notified as IN data of its own slave.

[0005]

However, in such a conventional PLC remote I / O system, when a failure occurs in the remote output slave, another remote slave is required to notify the remote master of failure information. In addition to the necessity, there is a problem that the actual I / O bit of the PLC is consumed because the IN data bit is used.

Further, even when a failure occurs in the remote input slave or the remote input / output slave, the I assigned to the own node for notifying the master of the failure information.
Since I use N data bits, I / O of PLC
The problem of consuming bits remains.

Further, in the above-mentioned conventional failure notification system,
Since only the failure information is notified to the master, there is also a problem that the failure processing in the remote slave in which the failure has occurred needs to be processed by the user program on the remote master side based on the failure information.

Therefore, the present invention has been made in view of such a problem, and the failure information can be notified to the remote master without using other remote slaves or the real I / O bit for IN data. It is an object of the present invention to provide a PLC remote I / O system capable of executing failure processing without imposing a burden on the user program on the remote master side.

[0009]

In order to achieve the above object, in the invention according to claim 1, the remote master and a remote slave connected to the remote master through a communication cable are provided, and the remote slave side is generated. PL that notifies the remote master side of the failure information
In the remote I / O system of C, the remote slave includes failure detection means for detecting a failure in the remote slave and outputting it as failure information, and the failure information output by the failure detection means in management information. Management information transmitting means for transmitting to the remote master.

According to a second aspect of the present invention, in the PLC remote I / O system according to the first aspect, the remote slave further sends a message from the remote master when the failure information is not output from the failure detecting means. It is characterized by further comprising output data storage means for holding the output data thus received and, when the failure information is output from the failure detection means, for clearing the output data sent from the remote master.

According to a third aspect of the present invention, in the PLC remote I / O system according to the first or second aspect, the failure detecting means detects an overcurrent in the remote slave and outputs it as failure information. It is characterized by

Therefore, in the present invention, when the failure detecting means in the remote slave detects a failure in the remote slave and outputs it as failure information, the management information transmitting means uses the real I / O bit for IN data. Instead, the failure information is included in the management information and transmitted to the remote master.

Further, in the output data storage means, when the failure information is not output from the failure detection means, the output data sent from the remote master is held, and when the failure information is output from the failure detection means. Causes the output data sent from the remote master to be cleared.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a PLC remote I / O system according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a remote I of a PLC according to the present invention.
2 shows the configuration of the / O system.

As shown in the figure, this remote I / O system is constructed by connecting one PLC main body 1 and three various remote slaves 2 to 4 via a communication cable 5.

This PLC main body 1 has 32 OUT / I
It has a master unit 11 which is a remote master having an N (input / output) table, an IN unit 12, and a CPU unit 13.

The remote input / output slave 2 has eight input / output terminals for input / output data, and the remote input slave 3 has eight input / output terminals for input data. Reference numeral 4 has eight output terminals for output data.

FIG. 2 shows the configuration of the remote input / output slave 2 on behalf of the configurations of the remote slaves 2-4.

The remote input / output slave 2 has an input / output I / F section 21, a failure detection section 22, and a communication control section 23, as shown in the figure.

The input / output I / F section 21 is composed of a power transistor or the like, and inputs / outputs eight points of input / output data in parallel between the communication control section 23 and an external load (not shown). Then, the data is taken in from the external load or the external load is driven.

The failure detection section 22 feeds back and monitors the drive current to the external load in the input / output I / F section 21 and the like, and when an overcurrent more than a predetermined value flows, it is detected by a short circuit and a failure occurs It is output as information.

The communication control section 23 comprises a communication I / F circuit 23a and an output buffer 23b.

The communication I / F circuit 23a transmits / receives serial input / output data to / from the PLC main body 1 via the communication cable 5, converts the serial input / output data into parallel data, and outputs it to the output buffer 23b. It is configured to be latched, and further, as the management information transmitting means, the failure information is stored in the management response frame and transmitted, or stored in the management information area of the response frame and transmitted.

The output buffer 23b is the communication I / F circuit 2
The parallel output data from 3a is latched, the failure information output from the failure detection unit 22 is input as a buffer clear signal, and the latched contents are cleared when there is a failure information output.

3A to 3C, the master unit 1
1 shows a method of transmitting and receiving failure information between the slave 1 and the remote slaves 2 to 4.

(A) shows a method of transmitting / receiving failure information when transmitting / receiving input / output data between the master unit 11 and the remote slaves 2 to 4 by the batch transmission / reception method. As shown in FIG. Data frame (not shown)
Management information response frame R dedicated to management information other than
It shows that failure information is stored in k together with management information (status).

(B) shows a method of transmitting and receiving failure information when input data is transmitted and received between the master unit 11 and the remote input / output slave 2 or the remote input slave 3 by the command response method.

That is, the master unit 11 transmits a command frame C1 including a header, a command, and an address to the remote input / output slave 2 and the like, while the remote input / output slave 2 and the like which received the command frame C1 receive the header , A response frame R1 including a response, an address, and IN data is returned. And
This response, which is a storage area for management information, includes status and failure information, which are management information.

(C) shows a method of transmitting / receiving failure information in the case of transmitting / receiving output data between the master unit 11 and the remote input / output slave 2 or the remote output slave 4 by the command response method.

That is, the master unit 11 transmits a command frame C2 including a header, a command, an address, and OUT data to the remote input / output slave 2 and the like, while receiving the command frame C2, the remote input / output slave 2 and the like. Returns a response frame R2 including a header, a response, and an address. Then, in this response, which is a storage area for management information, status and failure information, which are management information, are included.

Next, a failure detection process in the PLC remote I / O system configured as described above will be described.

First, for example, the remote input / output slave 2
When an overcurrent flows through the output to the external load in the input / output I / F unit 21 or the like, the failure detection unit 22 detects the overcurrent as a failure and outputs failure information.

Then, the failure information is input to the communication I / F circuit 23a in the communication control section 23 and the output buffer 23b.

The communication I / F circuit 23a includes a failure detecting section 22.
When the failure information is received from the
As shown in (a) to (c), the failure information is put in the management information response frame Rk or in the response storage area in the response frames R1 and R2, and the communication cable 5
To the master unit 11 to notify that there is a failure in this slave 2.

In the master unit 11, the master unit 11 receives the response frame, and the CPU unit 13 receives the failure information via the master unit 11 to know that a failure has occurred in the remote input / output slave 2. It will be possible.

Further, the output buffer 23b receives the failure information from the failure detecting section 22 before the communication I / F circuit 23.
The parallel output data from the master unit 11 is latched via a and is output to the external load by the input / output I / F section 21, but when the failure information from the failure detection section 22 is received, the failure information is buffered. It will be input as a clear signal to clear the contents that have been latched so far.

Therefore, the output buffer 23b does not output the output data to the external load connected to the remote input / output slave 2 by clearing the latch contents by the input of the failure information, so the master unit Failure processing can be performed in the slave in which the failure has occurred without going through the processing in 11, and damage to the external load or the like can be prevented in real time.

Therefore, according to the present embodiment, the failure information based on the failure that occurred in the remote slaves 2 to 4 is transmitted to the remote master not as IN data but as management information.
Effective I / O without consuming real I / O bit for N data
The O data bit is used to enable remote slave failure notification.

Further, according to the present embodiment, when a failure such as an overcurrent occurs on the remote slave 2 side, the output buffer 23b clears the latch content by inputting the failure information, and the remote input / output slave Since output data is not output to the external load connected to 2, the failure processing can be executed in real time without burdening the user program on the master unit 11 side.

[0041]

As described above, according to the present invention, since failure information is transmitted to the remote master as management information, not as IN data, the actual I / O bit for IN data in the response frame is consumed. Effectively without I
The / O data bit is used to enable remote slave failure notification.

Further, in the present invention, when a failure occurs on the remote slave side, the output data storage means clears the stored content by inputting the failure information and outputs the output data to the external load connected to this remote slave. Is not output, it becomes possible to execute failure processing in real time without imposing a burden on the user program on the remote master side.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a PLC remote I / O system according to the present invention.

FIG. 2 is a block diagram showing the configuration of a remote slave.

3A to 3C are explanatory diagrams showing a method of transmitting and receiving failure information between a remote master and a remote slave, respectively.

[Explanation of symbols]

 1 PLC body 2 Remote input / output slave (remote slave) 3 Remote input slave (remote slave) 4 Remote output slave (remote slave) 11 Master unit (remote master) 12 IN unit 13 CPU unit 21 Input / output I / F section 22 Failure Detection unit (fault detection unit) 23 Communication control unit 23a Communication I / F circuit 23b Output buffer (output data storage unit)

Claims (3)

[Claims] 1. A remote I of a PLC comprising a remote master and a remote slave connected to the remote master via a communication cable, and notifying failure information generated on the remote slave side to the remote master side.
/ O system, wherein the remote slave detects a failure in the remote slave and outputs it as failure information, and the remote master including the failure information output by the failure detection means in management information. A remote I / O system of PLC, comprising: a management information transmitting unit for transmitting to the PLC. 2. The remote slave further holds the output data sent from the remote master when the failure information is not output from the failure detection means, while the failure information is output from the failure detection means. The PLC remote I / O system according to claim 1, further comprising output data storage means for clearing output data sent from the remote master. 3. The PLC according to claim 1, wherein the failure detection means detects an overcurrent in the remote slave and outputs it as failure information.
Remote I / O system.