Why is the command Input edge sensetive?

The input Execute for the different Function Blocks described in this document always triggers the function with its rising edge. The reason for this is that with edge triggered Execute new input values may be commanded during execution of a previous command. The advantage of this method is a precise management of the instant a motion command is performed. Combining different Function Blocks is then easier in both centralized and decentralized models of axis management. The output Done can be used to trigger the next part of the movement. The example given below is intended to explain the behavior of the Function Block execution.

The following figure illustrates the sequence of three Function Blocks First, Second and Third controlling the same axis. These three Function Blocks could be for instance various absolute or relative move commands. When First is completed the motion its rising output First.Done triggers Second.Execute. The output Second.Done AND In13 triggers the Third.Execute.

Function Blocks to perform a complex movement