JPH05297933A - Execution time monitoring device for programmable controller - Google Patents

Abstract

PURPOSE:To early detect the program that discontinues the operation of a programmable controller PC by the delay of execution by providing an execution monitoring means which works periodically to monitor the execution time of a control program. CONSTITUTION:An identification code and a priority code under execution are written into a memory 5 pointed by a pointer 1 based on a control program before the start of execution of the program. Then, the control program monitoring periodically both the identification and priority codes reads the priority cods as well as a control program identification code under execution out of the memory 5 pointed by the pointer 1 and then adds (n) to a memory 4H and a memory 4L when priority code shows a higher order scan and a lower order scan respectively with the identification code used as an index. Thus, the execution time is stored in both memories 4H and 4L of a system memory within a single period of the control program set for each priority. In such a constitution, the control program that caused the delay of execution can be easily detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an execution time monitoring system for a programmable controller.

[0002]

2. Description of the Related Art In recent years, in a control system for industrial equipment, the speed and performance of the system have advanced, and the control contents of a programmable controller (hereinafter referred to as PC) have become complicated. Therefore, the control program by PC is
It is executed by dividing it for each response time corresponding to each control target. The operation by the PC is to take in input data from the outside through the input section, store it in the data memory, perform various arithmetic processing according to the control program, and after the arithmetic processing of the control program being executed is completed, update the data memory. Output the contents to the outside through the output unit.
The above operation sequence is called one scan, and a plurality of control programs assigned to a plurality of priorities are repeatedly executed at a scan cycle (same meaning as an execution cycle) predetermined for each priority. Each scan is executed by a central processing unit (hereinafter, CPU) in the PC by a control mechanism in the PC.
Called), and the priority of the interrupt level is set higher for those requiring a faster response. Therefore, the upper scan is executed by interrupting the lower scan. As a matter of course, the lower scan cannot be interrupted during the execution of the upper scan and is in a standby state. In a PC that is repeatedly executed at a predetermined scan cycle, a hardware timer (hereinafter referred to as a watch dog timer) that is generally set to several 100 msec is started prior to the execution of the repeatedly executed lower scan. However, the control program is being monitored for congestion. However, if the execution time is extended or the execution congestion occurs in some control programs for some reason, there is no guarantee that the watch dog timer will operate in the control program that caused it. Figure 5
Shows the operation status of the watch dog timer when an execution congestion occurs in some control programs of the lower scan. An operation example until the watch dog timer operates will be described based on FIG. That is, prior to the execution of the lower scan, the watch dog timer is activated and the input operation assigned to the lower scan is executed (FIG. 5). Then, the lower scan control programs P1 and P2 are executed, but if an upper scan execution request is issued while the control program P2 is being executed, the execution of the lower scan control program P2 is interrupted and the upper scan is executed (FIG. ). When the execution of the upper scan is completed, the execution control is resumed from the interrupted address of the control program P2 of the lower scan (FIG. 5). However, if execution congestion occurs for some reason (for example, an error in condition determination in repeated processing, overflow or underflow of calculation results) in the control program P2, it is the same even if a predetermined lower scan execution cycle is reached. Since the priority scan processing is not completed, the watch dog timer connects the count operation without restarting (FIG. 5), and the lower scan control program P2 is subsequently executed. At this time, if the above-described request for execution of the upper scan is generated, execution of the upper scan is started (FIG. 5). The watch dog timer started in Figure 5 operates during the upper scan (counts up)
Then, the PC stops in FIG. 5 and records that the execution congestion has occurred during the execution of the upper scan.

[0003]

As described above, the watch dog timer that monitors the execution congestion of the control program does not always stop within the control program that causes the execution congestion. Therefore, it takes a lot of time to find the control program that causes the execution congestion, and the PC is stopped for a long time, which has a great influence on the control target.

[0004]

In order to solve this gantry, a PC execution time monitoring device of the present invention comprises a storage means for storing an execution time for each divided control program.
Storage means for storing the identification code of the control program being executed, and each control that operates at a fixed cycle to monitor the execution time of the divided control program, independently of the execution cycle set for each priority. The program execution time monitoring means is provided.

[0005]

By using such means, it is possible to detect the control program that causes the error at an early stage when the operation of the PC is stopped due to traffic congestion. Therefore, it is possible to shorten the time for which the PC is stopped due to a defective program or the like. It will be possible.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. A programmable controller (PC) 1 includes a program memory 1 storing a control program created by a user and an external input / output device. A data memory 2 that stores output data and various data during operation of the PC, an arithmetic processing unit 3 that executes according to the contents stored in the program memory, an execution time storage unit 4 of the control program, and a running program. From the system memory 6 including the identification code storage unit 5 of the control program, the communication control unit 7 that controls communication with the program input device 9, and the input / output interface unit 8 that interfaces with external input / output devices. It is configured. FIG. 2 is an explanatory diagram of the execution time storage unit 4 (hereinafter referred to as the memory 4) incorporated in the system memory, which is arranged by priority according to the identification code of the control program, and the execution time of each control program is independently set. Remember. Memory 4H is for upper scan,
The memory 4L is an execution time storage memory of the lower scan group. For example, +11 in FIG. 2 indicates that the identification code executed in the lower scan stores the execution time of the control program of Pid02. The memory 4H,
In 4L, all areas are set to 0 at the start of execution of each priority, and only the execution time within one scan is stored. FIG. 3 shows an identification code storage unit 5 (hereinafter referred to as memory 5) that stores the identification code and the execution priority code of the control program being executed. Writing to and reading from the memory 5 are performed at the location indicated by the pointer 1. In FIG. 3, lvlo1 is data indicating the priority order of the control program currently being executed, for example, the execution time storage unit 4
The base addresses of the memories arranged according to the priority order of are stored. Pid03 is an identification code of the control program currently being executed. Next, the operation of the embodiment of the present invention will be described with reference to the flowchart of FIG. Generally, the divided control program is called from the main control program by a CALL instruction or the like. The divided control program decrements the pointer 1 shown in the memory 5 (FIG. 3) in the system memory in order to store the identification code of the control program and the priority code being executed (prior to starting the execution). 01), the identification code and the priority code being executed are written in the memory 5 indicated by the pointer 1, the identification code and the priority code of the control program currently being executed are stored (step-02), and the control program is executed (step-). 03). When the execution of the control program is completed, the pointer 1 is incremented (step-04) and the execution is returned to the caller (step-0).
5). Next, before executing the control program, the memory 5
The operation of the control program execution time monitoring for monitoring the identification code and the priority code stored in (1) at regular intervals will be described.
It is desirable from the viewpoint of accuracy of execution time monitoring that the fixed cycle time is set to a value that is sufficiently shorter than the execution cycle predetermined for each priority. Further, the time setting can be fixed or variable systematically. The control program identification code and the priority code being executed are read from the memory 5 pointed to by the pointer 1 (step-10). The read priority code is checked (step-11). If the priority code is the upper scan, n is stored in the memory 1H [identification code] using the read identification code as an index.
Is added (step 12). Here, n is a fixed cycle time during which the execution time monitoring operates. For example, if the fixed cycle time setting is 5 msec, n = 5. If the read priority code is the lower scan, n is added to the memory 4L [identification code] using the read identification code as an index (step 13). From the above, the execution time within one scan of the control program for each priority is stored in the memory 4H and the memory 4L in the system memory, and the execution congestion occurs in the control program and the PC When the stop occurs, the operator operates the program input device 7 to check the stored contents of the control program execution time storage area memory 4H and the memory 4L to easily find the control program causing the execution congestion. I can know.

[0007]

As described above, according to the present invention,
The program that caused the execution congestion can be found early,
The downtime of the PC can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of a programmable controller according to the present invention.

FIG. 2 is a diagram showing a storage mode of a memory that stores execution time.

FIG. 3 is a diagram showing a storage mode of a memory that stores an identification code.

FIG. 4 is a flowchart for explaining an operation program.

FIG. 5 is a diagram for explaining execution congestion in the related art.

[Explanation of symbols]

 1 Program Memory 2 Data Memory 3 Arithmetic Processing 4 Execution Time Storage 5 Identification Code Storage 6 System Memory 7 Communication Control 8 Input / Output Interface 9 Program Input Device

Claims (1)

[Claims] 1. A programmable controller for executing a control program divided into a plurality of units according to a priority order and an execution cycle arbitrarily set for each priority order, and a memory for storing an execution time for each of the divided control programs. Means, a storage means for storing an identification code of the control program being executed, and an execution cycle set for each of the priorities, independently of the execution cycle, in a fixed cycle to monitor the execution time of each divided control program. A programmable program characterized by having a control program execution time monitoring means that operates.
controller.