The time characteristics of cyclic service in Profibus

In Profibus master stations poll data from slave stations using the cyclic service CSRD (Cyclic Send and Request Data with Reply). Because the polling-interval determines the data sampling interval, it is important for the Profibus user to be able to know the maximum polling-interval of a cyclic service. We develop a formula for determining the maximum polling-interval of a cyclic service. Furthermore, if the polling-interval of a cyclic service cannot be met, then we can repeat the corresponding cyclic service in a poll list to reduce the polling-interval. However, how are the repealed cyclic services to be positioned in the poll list? The approach we use is an equi-distance one.