Siemens SIMATIC ST-1500 Function Manual page 35

The basics of counting, measurement and position detection
2.2 Basics of counting, measuring and position input (TM Count, TM PosInput, Compact CPU)
The figure below shows an example of the EN_CAPTURE and EVENT_CAP bits with use of
the Capture function by the rising edge at a digital input:
Note
The configured input filters delay the control signal of the corresponding digital input.
Hardware interrupt
You can configure a hardware interrupt for the Capture function. Individual hardware
interrupts may be lost if the hardware interrupt rate is higher than the system
acknowledgement rate. You can signal a lost hardware interrupt with a diagnostic interrupt.
34
Counting, measurement and position detection
Function Manual, 12/2017, A5E32009889-AG