The concept and process of SIMATIC S7-1500 PLC interrupt

(1) Interruption process

Interrupt processing is used to achieve a quick response to special internal or external events. When the CPU detects an interrupt request, it immediately responds to the interrupt and calls the interrupt program corresponding to the interrupt source, that is, the organization block OB. After executing the interrupt program, it returns to the interrupted program to continue executing the program. For example, when executing the main program OB1 block, the time interrupt block OB10 can interrupt the program being executed by the main program block OB1 and execute the program in the interrupt program block OB10 instead. After the program in the interrupt program block is executed, it will be transferred to the main program block OB1 and execute the main program from the breakpoint.

An event source is an interrupt event that can send an interrupt request to the PLC, such as date and time interrupts, delay interrupts, cycle interrupts, and interrupts caused by programming errors.

(2) OB priority

The execution of an organization block OB call can interrupt the execution of another OB. Whether an OB allows another OB to interrupt depends on its priority. SIMATIC S7-1500 PLC supports a total of 26 priorities, 1 is the lowest and 26 is the highest. A high-priority OB can interrupt a low-priority OB. For example, the priority of OB10 is 2, and the priority of OB1 is 1, so OB10 can interrupt OB1. S7-300/400 CPU supports 29 priorities.

The types and priorities of organization blocks will be announced in the next issue.

illustrate:

1. The S7-300/400 CPU only supports one main program block OB1, while the SIMATIC S7-1500 PLC supports up to 100 main programs, but the second main program number starts from 123 and is set by the configuration. For example, OB123 can be configured as the main program.

2. Cyclic interrupts can be OB30 to OB38. If they are not enough, you can also use OB123 and above organization blocks through configuration;

3. The startup organization blocks of S7-300/400 CPU are OB100, OB101 and OB102, but SIMATIC S7-1500 PLC does not support OB101 and OB102.