Siemens simatic s7-400 FM 450-1, User Manual, Page: 73 / 130

Modes, settings, parameters and commands
8.12 Initiating a process interrupt
Counter module FM 450-1
Manual, 02/2014, A5E03648739-02
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8.6 Periodic counting
Overview
In this mode an FM 450-1 counter counts once from the load value up to the count limit,
jumps back to the load value and continues to count.
Select gate function
In this mode you can select the gate function Options:
● SW gate
● HW gate, level-controlled or edge-controlled
Figure 8-3 Periodic counting with load value and gate function
Open and close SW gate
You open and close the SW gate and set the counter to the load value by setting or resetting
the relevant bit in the DB of the FC°CNT_CTRL in the user program (see chapter
"Assignment of the DB (Page 103)"). When you open the SW gate, the FM 450-1 starts
counting from the load value.
Action Initiating event
Open SW gate Set SW_GATE
Close SW gate Reset SW_GATE
If you want to restart the counter, you must reset the bit. The counter then starts counting
from the load value.