Understand the interrupt function of PLC cycle of input, process and output

PLC so understand the interrupt function, in understanding is interrupted, the first thing to know that PLC controller cycle of operation or scan cycle, it is necessary to say of PLC sequence control loop execution process, this is the premise of understanding the interrupt, must grasp, is divided into three parts, input, process, output processing,

1, input processing, programmable controller before the execution procedures, the programmable controller of all input terminal ON/OFF state of the reading input image area, the execution of a program even if the input changes, also won't change the contents of the input image area, in the execution of the next cycle of input processing read the changes.

2, process and content of PLC controller according to the instructions of the program memory, from the input image and the image of the other soft components area read all the ON/OFF state of soft component, and then from zero step began operation in order, and each time the results in writing to the image area. As a result, the soft components of image area with the execution of the program to gradually change the content, in addition, the output relay internal contact according to the contents of the output image area and to perform an action.

3, output, processing, all at the end of the instruction execution, the output Y in the image area, the ON/OFF state will be sent to the output latch memory, the programmable controller as the actual output.

the time required to perform as an action is also called scanning operation cycle time, so what is the connection interruption and scan cycle, interrupt is not full execution according to the order from top to bottom, but the interrupt program first run separately processing and output are not involved in the whole cycle operation immediately.

what is the function of interruption, we know the PLC scan cycle is very short, so it is hard to see how PLC sequence control execution process, here we might as well assume that scan cycle of 10 s of time, is to perform all the program needs to 10 s of time, there is a very simple program LD X0, OUT Y0, according to the above when X0 to ON, Y0 is not immediately have output, but the output until after 10 s, disconnect after X0, Y0 also not immediately shut down, all need to get after the scan is the result. So for us in the practical application of PLC is no used equipment couldn't work, then need to interrupt handling, USES the input interrupt function, input executed immediately. Actually PLC operation time is very short only a few milliseconds, fully able to meet this need, but some such as high-frequency pulse input, the capture of the pulse time in microsecond must be under the influence of cycle operation.

so if in a cycle to accomplish a lot of time ON/OFF state handling, must use the interrupt function. In we usually rarely use interrupt, even need PLC controller high-speed instructions with the interrupt function need not oneself write interrupt subroutine, such as high-speed counter with the method of interruption of high-speed pulses from a particular input relay for processing, so no matter how much computing time can be counted, counts the result of the comparison of special instruction or using high-speed counter output immediately, or for the high-speed counter count with high-speed counter interrupt way to perform a particular program.

is not adopted for high frequency pulse counting high-speed counter to count, for example, we use the interrupt function to count for the high-speed input, example as follows, from EI to FEND is the main program, from a pointer I101 ( The interruption of input X0 pointer) Began to IRET is interrupt subroutine, whenever the induction to the X1 is executed delay subroutine will numerical immediately transferred to the D10, thus avoiding the influence of PLC operation cycle.

Shenzhen Coolmay Technology Co., Ltd. is recognized as one of the leading manufacturer of in China.Trust in us and make Shenzhen Coolmay Technology Co., Ltd. your plc manufacturers supplier. Our products will bring more economic value to you.
Shenzhen Coolmay Technology Co., Ltd. is one of leading programmable control systems plc manufacturers distributors. You can order , and accessories for your need. Meeting your business need is always our top priority. Any of your enquiry is warmly welcomed.
Shenzhen Coolmay Technology Co., Ltd. are providing this to you at very low cost. Our claims are only based on different feed-backs received from various clients and not based on self-judgment.
Shenzhen Coolmay Technology Co., Ltd. will give you a suitable price for purchasing plc manufacturers.
When you choose to buy instead of plc controller price, the money you save may allow you to buy multiple other necessities, more than you had initially planned on buying.