FB125详细用法参考以下文档
http://www.ad.siemens.com.cn/download/docMessage.aspx?ID=1118&loginID=&srno=&sendtime=

FB126是用于Profinet诊断的，FB125是用于Profibus诊断的。两者不可搞混。

FB125下载地址：
http://support.automation.siemens.com/CN/llisapi.dll?query=FB126&func=cslib.cssearch&content=adsearch%2Fadsearch.aspx&lang=zh&siteid=cseus&objaction=cssearch&searchinprim=0&nodeid0=4000024&x=18&y=10
FB126下载地址：
http://support.automation.siemens.com/CN/llisapi.dll?query=FB126&func=cslib.cssearch&content=adsearch%2Fadsearch.aspx&lang=zh&siteid=cseus&objaction=cssearch&searchinprim=0&nodeid0=4000024&x=18&y=10