Period calculation

This calculation is carried out free-running in the slave without reference to the distributed clocks system. It is therefore independent of the DC mode.
During each cycle the interval between two positive edges of input A is counted.
Depending on the setting, periods of up to 1.6 s or 3.2 s (only for EL5151) in length are measurable.
If no edge change occurs for approx. 1.6 s, any period specification is cancelled.