DSAX110A 3BSE018291R1 ABB

When designing a control system with PLC,it is necessary to know how long it takes for the PLC to have a corresponding output signal after an input signal,otherwise,the coordination problem between the various components of the system cannot be solved correctly and accurately.It can be seen from the working process of the PLC:when the PLC works in the program execution stage,even if the input state changes,that is,the content of the input state register changes,the input signal executed by the CPU will not change.The input and output refresh stages are valid.In the same way,the output signal temporarily stored in the output status register can only be output to the output components in a centralized manner until the input and output refresh phases of the next scan cycle.The time required from the PLC receiving an input signal to the PLC outputting a control signal to the output terminal is the I/O response time of the PLC.

用PLC设计一个控制系统时，必须知道有了一个输入信号后PLC经过多长时间才能有一个对应的输出信号，否则，就不能正确并精确地解决系统各部件之间的配合问题。从PLC的工作过程可知：当PLC工作在程序执行阶段时，既使输入状态发生了变化，即输入状态寄存器的内容发生变化，CPU执行的输入信号也不会变化，而要到下个周期的输入、输出刷新阶段，才能有效。同理，暂存在输出状态寄存器中的输出信号，也要等到下一个扫描周期的输入、输出刷新阶段，才能集中输出给输出部件。从PLC收到一个输入信号到PLC向输出端输出一个控制信号所需的时间，就是PLC的I/O响应时间。