JPH0392904A - Programmable controller - Google Patents

Abstract

PURPOSE:To improve precision for executing a timer instruction by measuring the execution time of a user program for each cycle time, generating an interruption signal when the program execution time exceeds the minimum measuring time of a reference clock, and executing an updata processing to the current value of a timer element while referring the reference clock. CONSTITUTION:A programmable controller is composed of a CPU 2, system memory 3, work memory 4, user program memory 5, I/O memory 6, clock generating means 8, interface circuit 9 and cycle time measuring means 7. A common processing, the execution processing of the user program and an I/O refresh processing are cyclically executed and for each cycle time when these processings are once turned around, the execution time of the user program is measured. When the program execution time exceeds the minimum measuring time of the reference clock, the interruption signal is generated. When the interruption signal is generated, the update processing is executed to the current value of the timer element is executed by referring the reference clock. Thus, the delay of the update processing based on the reference clock is prevented and the precision can be made exact for executing the timer instruction.

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a programmable controller (hereinafter referred to as PC) having a timer instruction function that operates based on a built-in reference clock.

<<Prior Art>> In a PC having a timer instruction function, update processing for decrementing or incrementing the current value of a timer element is performed based on a built-in reference clock. The reference clock is configured so that its state value is inverted at regular intervals, and the state value of this reference clock is checked at a predetermined tie interval to ensure that the state value of the reference clock is the same as the last time it was checked. If they are different, it is determined that updating is necessary and the current value of the timer element is updated. If it is the same as the last time it was checked, it is determined that no update is necessary and the current value of the timer element is not updated.

Here, the timing to determine the timer update is when the timer element instruction is executed while the user program is running;
There are cases where common processing is in progress after the user program has completed one cycle of execution. <<Problems to be Solved by the Invention>> However, in the case of the former timer update timing, as shown in FIG.
If it extends beyond s), the timer may not be updated even though more than 100 ms has passed since the previous and current reference clock values are both on. Similarly, in the latter case, as shown in Figure 7, if the scan time required for program execution extends beyond the reference clock count unit (100 μs in the figure),
As shown in the timing (2), even though 100 ms or more has elapsed, since the previous and current reference clock values are the same, the updated value may be 0, that is, the timer may not be updated.

These phenomena occur more frequently as the amount of user program processing increases, resulting in a problem of delaying the execution timing of timer instructions.

Therefore, the present invention was made to solve the above problem, and its purpose is to prevent delays in update processing based on the reference clock even when the user program processing time becomes long, and to prevent the timer instruction from being delayed. The purpose is to provide a PC with accurate execution accuracy.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a programmable controller that updates the current value of a timer element set in a timer instruction using a built-in reference clock. means for measuring the execution time of the user program; and means for comparing the measured program execution time with a minimum measurement time of a reference clock and generating an interrupt signal when the program execution time exceeds the minimum measurement time of the reference clock. The present invention is characterized by comprising means for updating the current value of a timer element by referring to a reference clock when an interrupt signal is generated.

<Operation> In this invention, the execution time of the user program is measured for each cycle time, and an interrupt signal is generated when the program execution time exceeds the minimum measurement time of the reference clock. When an interrupt signal is generated, the current value of the timer element is updated by referring to the reference clock, so that the update process of the timer element is not omitted even if the program execution time is prolonged. (Example) Next, an example of the present invention will be described based on the drawings. Fig. 1 is a block diagram showing the hardware configuration of a PC to which this invention is applied. CP connected by bus l to
U2, system memory 3, work memory 4, user program memory 5, I/O memory 6, clock generation means 8
, an interface circuit 9, and a cycle time measuring means 7, which is a feature of the present invention. The interface circuit 9 also includes external input/output devices 11.1.
2nd class is connected. This PC realizes various functions as a PC by having a CPU 2 execute a system program stored in a system memory 3.

FIG. 2 is a general flowchart showing an outline of the operation of the PC described above.

As shown in the figure, common processing, user program execution processing, and I/O refresh processing are executed cyclically, and the time it takes for these processing to complete one cycle is called cycle time. Next, the specific operation of this invention will be explained based on the flowchart shown in FIG. First, when the user program starts executing, measurement of execution time is started (step 301). After the user program has been executed for a predetermined amount (step 302), it is checked whether the measured value of the execution time is 100++ seconds or more, which is the minimum unit time of the reference clock generated from the clock generation means 8 (step 302). 304). If the measured value of the execution time does not exceed the minimum unit time 100IIIs (No in step 304), steps 302 to 304 are repeated until the execution time exceeds the minimum unit time 100IIIs. If the measured value of the execution time exceeds the minimum unit time of 100 ms (Yes at step 304), update the current value of the timer set in the user program by interrupt processing (step 305), and reset the measured value of the execution time. (step 306), and continues to monitor the execution process and execution time of the user program (steps 302 to 306).
306). These processes are repeated until the cycle time ends and the process shifts to common processing.

Note that the amount of execution of the user program set in step 302 is a sufficiently smaller amount than the minimum unit time of the reference clock.

Also, in the common processing after the user program execution processing described above, the processing of monitoring the reference clock and updating the timer is performed as in the past. FIG. 4 is a flowchart showing another embodiment. In this embodiment, before starting execution of the user program, an interrupt timer is reset (step 401),
Furthermore, the interrupt mask is canceled (step 402).
). Next, execution of the user program is started (step 403). During this time, the execution time of the user program is monitored by an interrupt timer, and when a predetermined time has elapsed, the current value of the timer is updated by an interrupt (step 404).
). Furthermore, after resetting the interrupt timer (step 405), the process returns to user program execution (
Step 406). By repeating these processes thereafter, updating of the timer will not be omitted even if the execution time of the user program becomes long.

FIG. 5 is a timing chart showing the processing progress of the above embodiment. As shown in the figure, time is measured from the beginning of the instruction execution process, and before the clock is inverted at the interrupt when Looms has passed, the current value of the stored TIMNI1 is updated. Measurement of elapsed time will continue after being reset. By constructing the above embodiment as described above, the following advantages can be obtained. (]) The current value of the timer element will no longer be incorrect, regardless of changes in the timing interval for updating the current value of the timer element. (2) The error in the current value can be reduced without making the minimum measurement time of the reference clock smaller than the minimum measurement unit time of the timer element. (3) Except when the execution processing time of the user program becomes longer than the minimum measurement unit time of the reference clock, update processing is performed according to the normal execution procedure, so there is almost no overhead time in normal times.

<<Effects of the Invention>> As described above, the present invention measures the execution time of a user program at each cycle time, and generates an interrupt signal when the program execution time exceeds the minimum measurement time of the reference clock. When an interrupt signal is generated, the current value of the timer element is updated by referring to the reference clock, so even if the user program processing time becomes longer, the delay in update processing based on the reference clock can be avoided. It is possible to prevent this and improve the accuracy of timer instruction execution.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the hardware configuration of a PC to which this invention is applied, Fig. 2 is a general flowchart showing an outline of the operation, Fig. 3 is a flowchart showing the operation, and Fig. 4 is a general flowchart showing the outline of the operation. A flowchart showing an example,
FIG. 5 is a timing chart showing the processing progress, and FIGS. 6 and 7 are timing charts showing conventional examples. l...Bus 2...CPU 3...System memory 4...Work memory 5...User program memory 6...■/○ Memory 7...Cycle time measuring means 8...Clock Generating means 9... Interface circuit 1 1... Input/output device 12... Input/output device

Claims (1)

[Claims] 1. In a programmable controller that updates the current value of a timer element set in a timer instruction using a built-in reference clock, means for measuring the execution time of a user program for each cycle time; A means for comparing the specified program execution time with the minimum measurement time of the reference clock and generating an interrupt signal when the program execution time exceeds the minimum measurement time of the reference clock; A programmable controller comprising: means for referencing and updating the current value of a timer element;