Siemens SIMATIC ET 200S Operating Instructions Manual page 130

1Count5V/500kHz
3.6 Count Modes
The internal gate is automatically closed in the event of an overflow/underflow at the count
limits. To restart counting, you have to open the gate again.
Figure 3-3
With an interrupting gate function, the count remains at the underflow when the gate is
started.
Figure 3-4
130
Once-Only Counting Without Main Count Direction; Terminating Gate Function
Once-Only Counting with Up as the Main Count Direction
Technological Functions
Operating Instructions, 02/2007, A5E00124867-05