I have some error message after a power interruption in my WinCC HMI. No trending is happening after that. But, if I disconnect the OP270 in the same Profibus network, then WinCC error disappears and the trending starts. The OP270 is connected to a CPU 313C. whereas the WinCC(CP5611) is connected to S7-414-2DP. The 414-2DP is the master and the 313C is the slave. But, both the CPUs have independent programs and control different sections. The tags used in trending in WinCC is related to the CPU313C tags, which are communicated thro' CP342-5.