Introduction to the Mitsubishi FX PLC Outage Service

1. What is suspension?

The so-called suspension refers to the fact that in the process of sequentially performing the program scanning, when there is a request to respond immediately, the scanning work performed at that time is immediately suspended, and the service work specified in the request is performed first. After the service job is completed, return to the place where it was aborted and continue to perform the program scanning job.

In other words, aborting the service is like an abrasive goblin that interrupts the PLC's operations from time to time, and the PLC can't ignore it. As soon as the little goblin came, the PLC had to entertain it immediately, and after it was satisfied with the service, the PLC could continue the interrupted operation.

1. Abort the source

Obviously, abort is also a kind of procedural process handling, but this kind of handling is mostly randomly generated, such as fault alarms, external equipment actions, etc. Who gave the supplication for a cessation? In fact, the device that sends out the abort plea is called the abort source, and the abort source can be used for various external switching signals, as well as for the internal timer and counter of the PLC.

The PLC performs the abort source of the abort service, which is distinguished by the abort pointer of different labels, and we will continue to discuss this content when we talk about the abort instruction below.

2. Break point and return

After receiving the suspension request, the PLC will generate a breakpoint in the program, and after the abort service performance is completed, the PLC will return to the breakpoint, which is the so-called suspension back, and continue to perform the interrupted program at the breakpoint.

The breakpoint and abort back of the abort service program are obviously similar to the breakpoint and the return of the subroutine service program, and the abort service program and the subroutine are both in the sub-program area, and both use pointers as the import address number. However, the pointer used by the subroutine is the branch pointer P, and the pointer used by the abort service program is the abort pointer I.

3. Suspension of performance and priority

The PLC can only suspend the service if it agrees to do so, and if it is necessary to do so upon receipt of the request for suspension, the PLC will be able to handle the suspension service procedure immediately, regardless of whether the PLC is performing the main procedure or the sub-procedure at that time.

In addition, the PLC can only perform one abort service procedure at any one time, and there will be two situations at this time.

(1) The PLC has not yet performed the termination service procedure, when there are multiple suspension requests at the same time: the PLC places the priority according to the number of the suspension pointer, and the smaller the number, the higher the priority, it will be processed first, for example, I000 takes precedence over I100, and I100 takes precedence over I500.

(2) When the PLC is performing the suspension service procedure, there are other new suspension pleas: At this time, it is necessary for the PLC to continue to perform the suspension service procedure at that time before it can perform other suspension service procedures, that is, it is handled according to the principle of time priority. After all, the PLC boss has limited energy, and the goblin No. 1 comes first, so the PLC will serve No. 1 first, and the one who comes later will line up obediently, and it will not be missed.

4. Suspend the preparation of service procedures

The abort service program is the same as the subprogram, both are written in the subprogram area, but the call of the subroutine uses the CALL instruction, and as long as the driving condition is established, the PLC will go to the subprogram specified in the CALL instruction to perform the subprogram, and the subprogram returns to the main program after the subprogram returns to the instruction SRET.

The performance of the abort service program does not rely on the soft components, but the hardware circuit sends a abort signal to the PLC, and the PLC automatically identifies the abort request, and then finds the corresponding import to perform the corresponding abort service program, until the fulfillment of the abort return instruction IRET comes back to the breakpoint (in the main program or subprogram) and continues to perform downward.

It is conceivable that in front of the sub-program, it is a father to terminate the service program. It is important to note that the "shorter the better" principle should be followed when planning to terminate the service program, because the time for the service program to be suspended is too long, which will affect the performance control of the main program.

Knowing oneself and knowing one's opponent is the only way to win a hundred battles, and after we know what a suspension is, the next thing is to attack it!

Introduction to the Mitsubishi FX PLC Outage Service

Introduction to the Mitsubishi FX PLC Outage Service

2. Suspension of Instructions

Mitsubishi FX PLC has three abort instructions: EI, DI, and IRET.

1. Suspend the EI of the Consent Directive

After fulfilling the suspension agreement, the PLC will respond to the request for suspension in the process of performing the next procedures and perform the corresponding suspension service procedures.

The EI instruction is like an open door, and with this open door, the PLC is able to entertain and abort this little goblin, just like any door of Doraemon, so EI is also known as the opening and abort instruction.

Although the EI command can be turned on and aborted, it can't be turned off. The EI door that the dream took out was already open, so what if we didn't want the PLC to entertain this little goblin? Let's keep looking.

2. Suspend the stop instruction DI

After fulfilling the EI directive, if you do not want certain segments to be suspended, you can write a stop order DI before that segment. After the implementation of the DI directive, the PLC will not respond to any request for suspension in the course of the subsequent procedures. The DI instruction is like a locked door, with this locked door, the PLC can withstand the temptation of the little goblin to stop it, and ignore it, so the DI instruction is also known as the shutdown instruction.

After knowing the suspension of the consent order and the suspension of the stop order, let's continue to look at the suspension back order.

3. Abort the IRET instruction

In the process of performing the suspension service program, the PLC will unconditionally return to the breakpoint of the main program or subprogram to continue to perform when it fulfills the IRET. Its use is very different from the use of SRET when a subroutine comes back to command, except that one is used to abort and one is used to subroutine.

The PLC performs the abort service of which abort source is distinguished by the abort pointers of different labels, let's discuss the abort pointers of these different labels.

3. Abort pointer I and its abort source

As can be seen from the above, according to the number of the abort pointer, we can divide the abort source into three categories.

1. External input is aborted

The plea signal for external input abort is actually the switching signal of input port X0-X5, and when X0-X5 is used for abort, once connected, it will send a stop plea to the PLC. External input aborts are often used to handle external emergencies, such as alarms.

The 6 input ports X0-X5 correspond to 12 abort pointers, and are equipped with corresponding stop abort relays. These stop abort relays are obviously different from the stop instructions we mentioned above. Once the DI directive has been fulfilled, all requests for suspension are not responded to during the subsequent performance of the procedure, but the suspension relay is only for certain suspension pleas.

The designator of the external abort pointer is obviously related to the number of its input port, and there are rising and falling edges, but for the same port, the rising edge abort pointer and the falling edge abort pointer cannot be written at the same time.

2. The internal timer is aborted

An internal watchful abort is an abort that occurs automatically on a punctual basis, regardless of the scan cycle. It is suitable for applications where the scanning time is long but the data needs to be processed in a timely manner, such as punctual sampling of analog quantities.

The punctual abort pointer is similar to the external input abort pointer, and its label also has its corresponding connection, and because the punctual abort pointer is only 3, and can not be reused, obviously, only 3 punctual aborts can be set in a program.

3. The high-speed counter is aborted

It is necessary to use the high-speed counter abort in conjunction with the high-speed counter instruction DHSCS, and when the current value of the high-speed counter is equal to the set value, the abort service procedure referred to by the abort pointer is performed. The high-speed counter abort can be used for high-speed positioning control, etc.

The abort pointer used corresponds to the stop abort relay as long as one M8059, and when the M8059 is turned on, all high-speed counter aborts are stopped.

Similarly, since there are 6 high-speed counter abort pointers and cannot be reused, it is obvious that only 6 high-speed counter aborts can be set in a program.

Introduction to the Mitsubishi FX PLC Outage Service

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