I am using a ProTool Pro CS V6.0 SP 2 to build an HMI on a PC. On running the Run Time an Overflow error message appears resulted fromno exchange data with the PLC, as shown in the attachedscreen.

I need to know the reason of the overflow and how can I solve it if anybody knows.

the system consists of a PLC (CPU314) which controls a process two HMIs one of them is the PC and the other is an OP77a, the communication protocol is MPI with 187.5 Baud rate the PC contains a CP5611 PCI-Card all the communication cables are profibus cables number of power tags 74, only 22 of them are to be read continuously. System clock of the controller 5*100 ms and the acquisition cycle of the 22 read continuously tag is 3.5&6s.