Megmeet PLC - What are the features of the PLC program?

1. Correctness (low debugging cost)

First of all, the PLC program must be able to work correctly to meet the requirements of the actual control process. This is the essence of the PLC program, and if you don't do that, nothing else makes sense.

2. Reliability (low maintenance cost)

Not only to be right, but also to be reliable. You can't have problems every now and then in three days.

Reliability reflects the long-term stability of the PLC program, which is also the basic requirement for the PLC program. Some PLC programs can work correctly under normal working conditions or legal operation, but after abnormal working conditions (such as temporary power failure, and power on soon) or illegal operation (such as some buttons are pressed out of order, or several buttons are pressed at the same time or pressed many times in a row), the program can not work normally. This kind of program is not very reliable, or unstable, and it is a bad program. A good PLC program can identify the occurrence of abnormal working conditions, and can connect it with normal conditions, so that the program can adapt to a variety of situations, and a good PLC program can refuse illegal operations without leaving "traces". Only legal operations, i.e., preventative robust programming, are accepted. Interlocking is a common means of rejecting illegal operation, and this method is commonly used in relay circuits, and PLCs and system integrators can also inherit this method.

3. Readability (low learning cost)

The designed program is required to be readable, easy to understand, easy to debug, easy for others to read and use your program, and easy to maintain; If necessary, the program can also be used as a standard template for easy promotion.

To make the program readable:

1) The design context of the program should be as clear as possible, and the structure should be hierarchical;

2) Modularization of the functional layer, or design using an object-oriented approach;

3) Use some standard designs and universal designs;

4) The variable layer should be programmed with symbolic names as much as possible;

5) Parameters are set immediately before they are used (set and use);

6) I/O address allocation should be regular, easy to remember and understand;

7) The use of internal devices should also be regular, and the address allocation of the same function should maintain a certain discontinuous "fault margin" (for example, the address allocation of the X function is used to K, then the address allocation of the next function should not start from K+1, but from K+N) to prevent function changes;

8) If necessary, do some annotation work; Readability is something to keep in mind at the beginning of programming. It's not easy to do. Because in the process of program debugging, the increase or decrease of instructions and the change of the use of internal devices may make the original clearer program become a little chaotic. Therefore, there is a certain leeway for debugging to increase or decrease during the design, and then tidy up after the debugging is completed, so that the designed program has higher quality.

Megmeet PLC - What are the features of the PLC program?

Megmeet PLC - What are the features of the PLC program?

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