Siemens SIMATIC ST-1500 Function Manual page 27

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 for continuing the counting process after an overflow
and setting the counter to the start value:
The figure below shows an example for terminating counting after an overflow and setting
the counter to the opposite counting limit:
The figure below shows an example for continuing the counting process after an overflow
and setting the counter to the opposite counting limit:
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Counting, measurement and position detection
Function Manual, 12/2017, A5E32009889-AG