FOXBORO FBM215 福克斯波罗 输入/输出模块

FOXBORO FBM215 福克斯波罗 输入/输出模块

PLC在运行状态时，执行一个扫描操作所需要的时间为一个周期，这个是PLC的重要指标之一，其值为扫描周期T=（输入—点时间*输入端子数）+（指令执行速度*指令的条数）+（输出一点时间*输出端子数）+故障诊断时间+通讯时间

从上式可看出，扫描周期已经决定了：

1.CPU执行指令的速度

2.执行每条指令所占用的时间

3.程序中指令条数的多少

指令执行所需的时间和用户程序的长短、指令的种类和CPU执行速度是有很大关系，一般来说，一个扫描的过程中，故障诊断时间，通信时间，输入采样和输出刷新所占的时间较少，执行的时间是占了绝大部分。

PLC in the running state, the time required to perform a scan operation is a cycle, this is one of the important indicators of PLC, its value is scan cycle T= (input - point time * number of input terminals) + (instruction execution speed * number of instructions) + (output point time * number of output terminals) + fault diagnosis time + communication time

As can be seen from the above formula, the scanning cycle has been determined:

1.CPU execution speed

2. Time used to execute each command

3. The number of instructions in the program

The time required for instruction execution and the length of the user program, the type of instruction and the CPU execution speed are very related, generally speaking, in the process of a scan, fault diagnosis time, communication time, input sampling and output refresh take less time, and the execution time accounts for the vast majority.