Through the free port mode communication protocol, accelerate the speed of communication between PLC, has met the systematic demand.

通过自由口通信协议，加快PLC之间的通信速度，满足了系统的要求。

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How to implement serial communication between S7-200 PLC and computer based on free port mode was described in detail in the paper.

详细介绍了在自由口模式下S7 - 200 PLC与计算机实现串行通信的方法，重点介绍了通信协议及其实现方法，并给出了编程实例。

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