由手册可以知道，EIP21单元反馈给CPU的单元状态，通信状态字为n+10至n+14

n的值为PLC IO表设置该EIP单元的起始地址

例如红框的这个EIP21单元反馈给CPU的单元状态，通信状态字位1525+10=1535.00--1539.15

The various kinds of data are stored in the allocated CIO Area words, which

are identified by the offset from the beginning word (n) allocated to each Unit.

There are two patterns for the layout of the allocated CIO Area words: the

default settings and user settings. The layout can be selected in the Status

Area settings in the Edit Parameters Dialog Box from the CX-Programmer.

To set a customer areas, select User defined for the Layout Type on the Status

Area Tab Page.

The beginning word n is calculated by the following equation:

Beginning word n = CIO 1500 + (25 × unit number)

以下为每个状态字的每个bit的详细解释

以下是（n+10）状态字具体Bit的详细解释

（n+10）.00----设备发生错误 （n+10）.01----网络发生错误

（n+10）.06----IP 地址重复错误 （n+10）.09----链路关闭错误

（n+10）.14----状态区域布局

我们可以通过查看EIP单元的手册知道剩余的状态字相应Bit的具体解释

这样我们就可以在PLC程序中读取相应的bit来判断该EIP单元的状态了