JPH0751611Y2 - Programmable controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a programmable controller.

(Prior Art) A programmable controller performs sequence control by repeatedly decoding and executing a sequence program including many instructions. One execution of the sequence program is called a cycle, and the time required for processing one cycle is called a scan time.

Conventionally, the following means has been devised as a means for activating the next cycle after one cycle of processing is completed.

(1) The zero crossing point of the voltage of the commercial power supply, that is, the power supply of the programmable controller is detected, and the cycle is started when the zero crossing point is detected. This is called the zero-cross method. The reason for starting the cycle at the zero-crossing point of the power supply voltage is to turn ON / OFF the process at the power supply voltage of 0 V to suppress noise generation.

(2) The END instruction provided in the sequence program ends the processing of the current cycle and immediately starts the processing of the next cycle.

(Problems to be solved by the invention) The scan time should be kept as constant as possible in order to maintain good timing of information exchange between the programmable controller and processes such as limit switch and solenoid valve. . However, the scan time has the following fluctuation factors. The sequence program is divided into an execution part and a non-execution part according to the state of the relay contact at the time of execution, but the ratio thereof changes every cycle depending on the change of the state of the relay contact. Therefore, the scan time also varies. That is, the larger the ratio of the executed portion, the longer the scan time. In addition, when input / output processing by communication such as remote I / O is added, it is necessary to wait for the completion of communication, but the time required for communication increases or decreases depending on the amount of communication in that cycle. Becomes When the scan time fluctuates, the timing of information exchange between the programmable controller and the process fluctuates, which causes normal control to become impossible.

The programmable controller using the conventional cycle starting means described above has a problem that the scan time varies.

When the means of the above (1) is used, assuming that the frequency of the commercial power source is 50 Hz, the start pulse is generated every half wavelength, that is, every 10 ms in terms of time. Therefore, even if the current cycle ends in 21ms, for example, the next cycle
It will not start until 30ms have passed. Therefore, the scan time becomes long as a whole, and the scan time greatly varies.

The means (2) is designed with the intention of shortening the scan time as compared with the case where the means (1) is used. However, even by this means, the problem of the fluctuation of the scan time described above cannot be solved. Therefore, in order to avoid variations in the timing of information exchange with the process, a program for adjusting the timing is inserted in the sequence program. Therefore, the sequence program becomes long and complicated, and a great deal of effort is required for debugging and maintenance.

The present invention has been made in view of such a current situation,
It is an object of the present invention to provide a programmable controller which can make the scan time constant without modifying the sequence program and can set an arbitrary scan time.

(Means for Solving the Problem) The programmable controller of the present invention repeats the sequence program by memorizing the scan time target value and immediately activating the next program execution cycle after the end of one program execution cycle. It has a program execution means for executing and setting a scan time target value in the storage means when the sequence program includes a scan time setting instruction.

The programmable controller further delays the start of the next program execution cycle until the scan time target value elapses when the scan time in executing the program by the program execution means is less than the scan time target value. Delaying means, determining means for determining whether or not an external signal is used to start a program execution cycle, and an external signal is input when the determining means determines to use the external signal. The second delay means is provided to delay the start of the next program execution cycle until the start.

When the programmable controller determines to use the signal from the outside, the next program execution cycle is performed only when the start delay of the program execution cycle by the first and second delay means is completed. When it is determined that the signal from the outside is not used, the next program execution cycle is started only when the delay of the start of the program execution cycle by the first delay means is completed. Is configured. Thereby, the above object is achieved.

(Operation) In the present invention, the storage means for storing the scan time target value is provided, and if the scan time in the program execution is less than the scan time target value of the storage means, the next scan time target value is passed until the scan time target value elapses. Since the start of the program execution cycle of is delayed,
It is possible to reduce variations in scan time without modifying the sequence program.

Further, since an arbitrary value can be stored as the scan time target value in the storage means, the scan time can be optimized in consideration of the operating speed of the external device connected to the programmable controller.

Furthermore, since the determination means for determining whether to use the signal from the outside for starting the program execution cycle is provided, the start of the program execution cycle is based on both the signal from the outside and the scan time target value. It is possible to realize both an operation mode in which the operation is performed based on the scan time target value and an operation mode in which the activation is performed based on only the scan time target value.

Here, when it is decided to use the signal from the outside, the start of the next program execution cycle is delayed until the signal from the outside is input after the lapse of the target value of the scan time. Therefore, even when an external device whose operating speed fluctuates is connected to the programmable controller, the program execution cycle can be started according to the operation delay of the external device, and on the other hand, when it is decided not to use a signal from the outside. The delay in the start of the program execution cycle is until the scan time target value elapses, and the reduction can be effectively performed while suppressing the variation in the scan time.

(Embodiment) An embodiment of the present invention will be described below.

FIG. 1 shows a block diagram of an embodiment of the present invention. CPU1
It operates according to the system program stored in the ROM 2 and executes the sequence program while exchanging information with the various memories, I / O units, etc. described below via the bus 3. A sequence program is stored in the program memory 4. The system memory 5 stores data necessary for executing the sequence program. RAM6 is used as working memory. Data input / output I / O unit 8 from input I / O unit 7
Data output to the I / O unit driver / receiver 9 is performed. A process 10 such as a limit switch or push button is connected to the input I / O unit 7. For output
A process 11 such as a lamp or a solenoid valve is connected to the I / O unit 8. The program device 12 is provided for inputting a sequence program and storing it in the program memory 4, and is connected to the bus 3 by RS-485 indicated by reference numeral 13. The power supply unit 14 supplies 5V DC power to each unit. When the external trigger input circuit 15 detects the external trigger signal, it sends the trigger signal 16 to the bus 3. The display unit 17 is for displaying a scan time target value described later or a time when the actual scan time exceeds the scan time target value. The display content of the display unit 17 can be switched using the display selection switch 18.

In this embodiment, a scan time target value is set in order to achieve a constant scan time. The scan time target value is input from the programming device 12 and stored in a predetermined memory cell in the system memory 5. The scan time target value can be set or changed by a scan time setting command that can be provided in the sequence program. As shown in FIG. 2, the scan time setting command is composed of a part 21 indicating the type of command and a part 22 indicating the scan time target value to be set. “**” in the part 21 is a number or the like and indicates the type of instruction. The scan time target value is expressed in BCD code, and its unit is millisecond. When the sequence program includes a scan time setting instruction, the scan time target value stored in the system memory 5 is rewritten, and a new scan time target value is used in the next cycle.

As the scan time target value, it is preferable to use the largest value among the measured values of the scan time obtained by performing the test operation. Further, since the scan time target value can be changed by the scan time setting command, the scan time target value once set can be flexibly adjusted according to the state of the external device such as the NC device or the robot.

The Shiriga signal 16 is used to activate a cycle, as will be described in detail later. Whether or not the trigger signal 16 is used to activate the cycle can be selected. Information on whether or not to use the trigger signal 16 is input from the programming device and stored in a predetermined storage cell of the system memory 5.

The operation of this embodiment will be described with reference to the flowchart of FIG.

(1) Initial setting process (steps 31 to 32) When the power is turned on, self-diagnosis is performed (step 3
1) Next, each part is initialized (step 3)
2).

(2) Cycle activation (steps 33-34) Examine system memory 5 and trigger signal for cycle activation
It is determined whether to use 16 (step 33). If the trigger signal 16 is not used, the cycle is activated immediately. When the trigger signal 16 is used, it is checked whether or not the trigger signal 16 is input, and if it is input, the cycle is started (step 34). If the trigger signal 16 is not input, the loop is waited until it is input.

(3) Set timer (step 35) Set the scan time target value stored in the system memory to the timer ST.TMR. The ST.TMR value is counted down during execution of the sequence program, with the set target value as the initial value.

(4) Execution of 1-cycle sequence program (steps 36 to 38) The sequence program is executed and input / output processing (step 36), calculation (step 37), communication, and peripheral tool processing (step 38) are performed. .

(5) Scan time processing (steps 39 to 42) When execution of the sequence program for one cycle is completed, it is checked whether or not the timer ST.TMR has already expired (step 39). If the timer ST.TMR has timed up, the actual scan time has exceeded the scan time target value, so the time over flag is set (step 40). If the timer ST.TMR has not expired, wait until the timer expires (step 4
1), reset the time-over flag (step 4)
2).

By the above processing of the scan time, the scan time can be kept constant even when one cycle ends earlier than the target.

The time-over flag indicates whether or not the scan time has exceeded the target value in the immediately preceding cycle, but this flag is not used for other processing.

(6) Change of scan time target value (steps 43 to 44) It is judged whether or not there is a scan time setting instruction in the sequence program in the cycle just finished (step 43). The scan time target value stored in the system memory 5 is changed (step 44).

After that, the processes of (2) to (6) described above are repeatedly performed, and at this time, when it is determined to use the trigger signal 16 from the outside, it is after the scan time target value has elapsed. Only when the trigger signal 16 from the outside is input, the next program execution cycle is started, and when it is determined not to use the signal 16 from the outside, only when the scan time target value has passed, The next program execution cycle will be started.

As described above, in the present embodiment, the system memory 5 for storing the scan time target value is provided, and when the scan time in the program execution is less than the scan time target value stored in the memory, the scan time target value elapses. Since the start of the next program execution cycle is delayed until that time, it is possible to reduce variations in scan time without modifying the sequence program.

In addition, since an arbitrary value as the scan time target value can be stored in the system memory 5 by the program device 12, the scan time should be optimized in consideration of the operating speed of the external device connected to the programmable controller. You can

Further, since the CPU 1 determines whether or not to use the external trigger signal 16 to start the program execution cycle, the start of the program execution cycle is determined by the external trigger signal 16 and the scan time target value. It is possible to implement both an operation mode based on both of the above and an operation mode in which the activation is performed based on only the scan time target value.

If it is decided to use the external trigger signal 16, the start of the next program execution cycle is delayed after the scan time target value has elapsed and until the external trigger signal 16 is input. Therefore, even when an external device whose operating speed fluctuates is connected to the programmable controller, the program execution cycle can be started according to the operation delay of the external device, while the external trigger signal is not used. If it is determined that the delay of the start of the program execution cycle is until the lapse of the scan time target value, the reduction can be effectively performed while suppressing the variation of the scan time.

(Effect of the Invention) According to the present invention, there is provided a programmable controller capable of easily realizing a constant scan time and setting an arbitrary scan time. Therefore, the scan time can be appropriately determined in consideration of the operating speed of the external device connected, and sufficient processing time can be taken for interrupt processing and the like. In the programmable controller of the present invention, since it is not necessary to insert a timing adjusting program into the sequence program, the memory for storing the sequence program is effectively used, and the time required for debugging and maintaining the sequence program is increased. Shortened. Since the programmable controller of the present invention has means for starting a cycle based on a signal from the outside, the cycle is adjusted according to the delay of the external device even when the external device whose operating speed fluctuates is connected and used. It is possible to start. In addition, the programmable controller of the present invention is. Since an arbitrary scan time can be set, it can easily replace the existing programmable controller that was operating at a slow processing speed.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a format of a scan time setting command in the embodiment, and FIG. 3 is a flow chart showing an operation of the embodiment. 1 …… CPU, 2 …… ROM, 3 …… Bus, 4 …… Program memory, 5 …… System memory, 6 …… RAM, 7 …… Input I / O unit, 8 …… Output I / O Unit, 9 …… I / O unit Bus driver / receiver, 10,11 …… Process, 12 …… Program device, 13 …… RS-485,14 …… Power supply unit, 15 …… External trigger input circuit, 16… … Trigger signal, 17 …… Display unit, 18 …… Display selection switch.

Claims (1)

[Scope of utility model registration request] 1. A storage means for storing a scan time target value, and immediately after the end of one program execution cycle, the next program execution cycle is started to repeatedly execute the sequence program, and the scan time setting instruction is given to the sequence program. Program execution means for setting the scan time target value in the storage means, and if the scan time in the program execution by the program execution means is less than the scan time target value, the scan time target value is First delay means for delaying the start of the next program execution cycle until the lapse of time, deciding means for deciding whether or not to use a signal from the outside for activating the program execution cycle, and the deciding means from the outside. External if it is decided to use the signal Second delay means for delaying the start of the next program execution cycle until these signals are input, and the first and second delay means when it is decided to use the signal from the outside. The next program execution cycle is started only when the delay of the start of the program execution cycle is completed, and when it is determined not to use the signal from the outside, the program execution cycle by the first delay means is executed. Programmable controller configured to start the next program execution cycle only when the start delay of is completed.