JPH01119804A - Scan time fixing system for programmable controller - Google Patents

Abstract

PURPOSE:To execute a sequence program by a prescribed scan time by executing the sequence program, and thereafter, comparing it with the maximum execution time up to the present and taking its difference and waiting for the next execution by its time difference. CONSTITUTION:A scan time T1' being in the course of operation at present and the maximum scan time T1 up to that time are compared, and when the present scan time T1' is shorter than the maximum scan time T1, an interruption flag is turned ON, and a value which has added a waiting time T4 to the scan time T1' being in the course of operation at present, and the maximum scan time T1 up to that time are compared. When both of them are equal, the present scan time T1' is cleared, the interruption flag is turned OFF and a time waiting processing is completed. Supposing the added value is shorter than the maximum scan time T1, the waiting time T4 is surther provided. Also, when the present scan time T1' is longer than the maximum scan time T1 up to that time, the present scan time T1' is registered as the maximum scan time T1, and a series of processings are completed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scan time constant method for a programmable controller.

(Prior Art) A processing method of a conventional programmable controller will be explained based on FIGS. 5 and 6. Figure 5 is a diagram showing the configuration of a programmable controller (hereinafter referred to as rPCJ).
), a data storage unit (4) that stores data in the peripheral device (2), and a calculation unit (5) that performs calculation processing based on the sequence program of the program storage unit (3). ) and an output unit (7).

Next, to explain the scan time of the programmable controller, the scan time is the time T required to execute the sequence program from the peripheral device (2) of the PC (1) from the 0th step to the end.
The 0N10FF information for operating this program is imported from the outside via the human power section (6), and based on that information, it is processed in the arithmetic section (5), and the arithmetic results are output via the output section (7). The time required for
The programmable controller operates based on a sequence program with the scan time as one cycle.

Normally, PC(1) performs a T10 refresh after executing the END process of the program, returns to step 0 and resumes execution, and this series of operations is repeated.

[Problems to be solved by the invention] Scan time T of conventional programmable controller
3 consists of the sum of the program execution time TI and the refresh time T2 as described above, but even if the sequence program is the same, the 0N10FF state may be different,
If an interrupt occurs during processing, there will be variations in the execution time T1, which will in turn cause variations in input/output control, which may cause trouble in controlling external devices.

The present invention has been made to solve the above problems,
The purpose of this invention is to stabilize the control of external equipment by making it possible to execute a sequence program with a constant scan time even if there are variations in the execution time T1.

[Means for solving problems]

The scan time running method of the programmable controller according to the present invention is that after the sequence program is executed, it is compared with the maximum execution time up to now using the time waiting processing program function, the difference is calculated, and the next execution is waited for the time difference. This is to make the scan time constant.

[Operation] According to the present invention, the maximum execution time T1 is always maintained despite variations in the execution time T1 due to the time waiting processing program function.
In order to add the time difference from MAX to the execution time T as a waiting time until the next execution, the scan time becomes constant as the sum of the maximum execution time TMAX and the refresh T2.

〔Example〕

Hereinafter, based on the embodiment shown in FIGS. 1 to 4, the same or equivalent parts as in the conventional art will be given the same reference numerals, and the description thereof will be omitted, and the description will focus on the features of the present invention. FIG. 1 is a flowchart showing the execution of a program equipped with a time waiting processing program function.
(Current scan time in the figure) and the maximum scan time up to that point are compared (step 100), and if the current scan time is shorter than the maximum scan time, turn on the interrupt flag (step 101), the currently active scan time Compare the value added by counter C (search for counter C in Figure 4) with the maximum scan time up to that point (step 102), and if the two are equal, clear the current scan time and turn off the interrupt flag. (Step 10
3) Complete the time waiting process. Temporarily step (102
), if the addition is shorter than the maximum scan time, the interrupt flag is turned ON again as shown in Figure 4 and the counter CH is added, that is, this process is repeated until the maximum scan time is reached by giving an additional waiting time and the maximum scan time is reached. When the time is reached, the above-described processing is performed.

Furthermore, if the current scan time is longer than the maximum scan time up to that point in step (100), the current scan time is registered as the maximum scan time and step (100) is performed.
04), a series of processes are completed at step (103) described above.

To explain the above-mentioned time interrupt based on FIG.
), count the required waiting time and step (201)
, performs the process in step (102) above.

To explain the fluctuation of the scan time mentioned above based on FIGS. 3 and 4, the actual execution time T1° is the maximum execution time T up to that point, and if it is shorter, the time waiting process is performed by the processing after step (101). By the program function, after the END processing of the execution program, the wait time T4 is added to make it equal to the maximum execution time T1, and the scan time T3 is made equal to the maximum scan time. Therefore, the scan time of the sequence program is successively fixed to the maximum scan time. In this case, the maximum scan time is updated sequentially as shown in FIG. 4, and becomes constant at the maximum scan time in the sequence program. In other words, if the first execution time has the maximum scan time in a series of sequential controls, then the scan time will be fixed. As described above, by making the scan time constant, control of external equipment becomes easier and stabilized.

[Effects of the Invention] As described above, according to the present invention, the scan time of the programmable controller can be made constant, making it easier to control external equipment and stabilizing the control.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing the scan time constant force formula according to the present invention, Fig. 2 is a flowchart showing the process of adjusting the waiting time in the time waiting fi filling, Fig. 3 is a diagram showing the scan time, and Fig. 4 is the scanning FIG. 5 is a block diagram showing the programmable controller, and FIG. 6 is a diagram corresponding to FIG. 3 showing the conventional scan time. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) After executing the sequence program created by the peripheral device of the programmable controller, compare the time required for its execution with the maximum execution time, wait for the time difference using the time waiting processing program function, and then execute the next execution. A scan time constant method for a programmable controller, characterized in that the scan time is constant in this manner. (2) The scan time constant method for a programmable controller according to claim 1, wherein the time waiting processing program function is provided after the END processing of the sequence program.