Cyclic frames may contain invalid cycle counter in IRT mode

Sometimes it may happen that the firmware sends out a cyclic IRT frame with a wrong cycle counter value (e.g. where only the "high" byte is incremented and the "low" byte is not, same cyclecounter). Depending on the configured network cycle time and DataHoldTime for the IOCR this may lead to abort of the connection enforeced by IO Controller with error "CPM Watchdog, DataHoldTimer expired".

The problem most likely occurs when the firmware has to serve a higher interrupt load around the cycle start timepoint.

The firmware is expected to send frames with proper cycle counter. The fix for this issue will change the internal timing behavior of the firmware: The firmware's time to prepare the DPM Input area will increase. Thus the device GSDML parameter T_IO_OutputMin might need increasing as well.