PLC scan cycle is introduced

The working process of the programmable controller includes two parts: the diagnosis and response of fixed communication process and the user program execution, as shown in figure 5 - 1. PLC in every time before execution of user programs, to implement fault self-diagnosis procedures, such as reset, surveillance, timing, internal fixed program, if the diagnosis is normal, continue to scan down, and then PLC controller check for communication with the programmer, computer and other requests. If there is a request of communication, such as computer, the corresponding processing. When the PLC in stopped ( 停止) Process of circulation state, only for the first two. In the PLC is running ( 运行) State, PLC controller from internal processing, communication operation, the input scan, execute user programs, the output refresh stage of five working cycle work. Every complete the above five stages needed time referred to as a scan cycle. Is an important indicator of PLC scan cycle, small PLC scan cycle for more than ten milliseconds to tens of milliseconds. PLC scan cycle length depends on the scanning speed and the length of the user program. Millisecond scan time for general industrial equipment is usually allowed, PLC to enter a short lag is allowed. But for some I/O quick response equipment, the corresponding treatment measures should be taken. Such as high speed CPU choice, improve the scanning speed; Choose fast response, high speed counting module and interrupt handling of different measures to reduce the time lag. As much as possible for users to improve the ability of programming, optimization programs; While in the control program of large equipment, as far as possible to reduce the length of the program, choose the branch or leapfrog program, etc. , can reduce the user program execution time.
Shenzhen Coolmay Technology Co., Ltd. devises a regular, independent, transparent and objective assessment mechanism to evaluate country performance.
Reach us at Coolmay PLC. We'll always try to give you the BEST deal on . If we can't, we'll at least give you some hel pful advice. Please use our experience!
Shenzhen Coolmay Technology Co., Ltd. manufactures plc manufacturers with innovative facilities and professional operation.
Shenzhen Coolmay Technology Co., Ltd. is the best manufacturer which has rich experience on manufacturing.