参考网址方法：
WinCC与S7-200SMART OPC通信(SIMATIC NET)
http://www.ad.siemens.com.cn/productportal/Prods/s7-200-smart-portal/200SmartTop/communication/OPC/STEP7OPC/WinCC_OPC.htm
SMART 200 OPC通信
http://www.ad.siemens.com.cn/productportal/Prods/s7-200-smart-portal/200SmartTop/SmartSMS/063.html