使用相对模式时，报警数据指定添加到当前值的报警值的正负变化。模块验证所请求的新报警限值是否超出范围，且不违反HIGH（高）>LOW（低）条件。如果发出无效请求以更改报警值，则相应的错误代码将在分配给模块的%I引用的个字节的高四位中返回。E2 COMMREQ示例以下梯形图逻辑提供了设置E2 COMMREQ数据并发出COMMREQ的示例。与所有COMMREQ一样，建议梯形图在启动另一个COMMREQ之前验证正在进行的E2 COMMREQ的完成情况。这确保模块接收COMMREQ的速度不会快于处理COMMREQ。一种方法是在启用COMMREQ时将COMMREQ状态（本例中为%R0001）的内容归零。由于已完成COMMREQ返回的状态从不为零，因此非零状态字将指示COMMREQ已完成。12 12-22系列When using relative mode, the alarm data specifies the positive or negative change in the alarm value that is added to the present value. The module verifies that the new alarm limit requested is not out of range and does not violate the condition HIGH>LOW. If an invalid request is made to change an alarm value, the corresponding error code will be returned in the upper four bits of the first byte of %I references assigned to the module. E2 COMMREQ Example The following ladder logic provides an example of setting up E2 COMMREQ data and issuing the COMMREQ. As with all COMMREQs, it is recommended that the ladder verify the completion of the E2 COMMREQ in progress before initiating another. This ensures that the module does not receive COMMREQs faster than it can process them. One way to do this is to zero the contents of the COMMREQ status (%R0001 in this example) as the COMMREQ is enabled. Since the status returned for a completed COMMREQ is never zero, a non-zero status word will then indicate that the COMMREQ has completed. 12 12-22 Series
