Improve PLC operating efficiency and shorten execution time when completing the same task.
Note: Beginners do not need to worry about the methods summarized in this article. Just focus on making the program easy to read and standardized, and complete the functional requirements.
1. When you can use a single character, try to avoid using double characters. When you can use an integer, try to avoid using a real number.
2. Prioritize the use of spare (non-hardware connection) IB , IW , ID , QB , QW , and QD , followed by M and S ;
3. Minimize data type conversions. If conversions are unavoidable, use AC to store intermediate variables to reduce the number of conversions. Alternatively, reserve storage space in advance during programming. For example, when using VW2 to store integers, leave VW0 unused, so that data in VW2 can be accessed directly using VD0 .
4. Reduce unnecessary network scans and classify network operations that can be conditionally executed (especially AIW and AQW ) into subroutines for conditional calls (e.g., timer interrupts).
5. Use the XOR instruction to invert any bit (this instruction is slightly difficult, and careful bit alignment is required during debugging; it is recommended to use binary numbers when programming).
6. While ensuring process requirements are met, appropriately reduce the frequency of interruptions;
7. Subroutines should minimize the number of conditional checks and standardize the input and output parameters of subroutines to reduce code redundancy.
8. For repetitive and time-consuming tasks, periodic processing should be adopted; this includes: distributing the initialization work across multiple cycles. Slightly differentiating the sampling times of multiple PID loops can prevent multiple interrupt calls within the same cycle, resulting in a more uniform and stable scan cycle.
9. For subroutine calls with little input data, you can first check if the input data has changed. If it has not changed (see post #48 for comparison methods ), you can skip the subroutine directly, thereby reducing the scanning cycle.
10. Try to arrange bit variables in the V area within V511.7 , and arrange frequently used VB/VW/VD variables within V4095 , which can shorten the program scan cycle.
11. If SM0.0 is connected in series with other signals, it only increases the program size and execution time, and has no other effect (if the network has already met the required contacts on the left, there is no need to connect SM0.0 in series ).
12. When there's no need to share signals, placing multiple instructions in the same network will generate additional push and pop operations (this can be analyzed using STL ). Furthermore, unless logically required, horizontal chaining should be avoided, as this can reduce at least one AND instruction. The only benefit is that placing them in one network makes the code feel more compact.
13. Use immediate I/O instructions reasonably (minimize their use) to save the PLC 's conversion time for processing immediate instructions.
14. Use the result storage as much as possible during calculations, and avoid using temporary storage.
