Siemens SIMATIC ET 200AL System Manual page 2195

The following figure shows an example of the behavior of LEC when a read-in job is started
with EdgeSel = 3 (rising and falling edge, order depending on occurrence).
T
APP
Rn
Fn
The module can count a maximum of seven edges per application cycle. LEC = 7 means
therefore that seven or more edges have been counted.
Reaction to error
The Error output indicates if the instruction was processed correctly. In the event of an error,
the cause of the error is displayed at the Status output.
High-precision input/output with Time-based IO
Function Manual, 11/2019, A5E33454822-AC
Application cycle
Specified times of a positive DI edge
Specified times of a falling DI edge
Programming
4.3 Time-based IO
37