The RTBWriteRes parameter is another indicator for evaluating the real-time process utilization. The setpoints of a Sercos cycle are not transmitted until the next cycle. This also means that the reference values must be available at this time. The parameter RTBWriteRes measures the time between the end of the RTP and the start of the MST. The value is cyclically monitored by the system. A negative value triggers the "8507 SERCOS write cycle overflow" diagnostic message.