Siemens simatic s7-400 FM 450-1, User Manual, Page: 69 / 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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8.4 Infinite counting
Overview
In this mode an FM 450-1 counter counts infinitely from the current counter status:
● When counting up, if the counter reaches the upper count limit and a further count pulse
comes, it jumps to the lower limit and continues counting from there without any pulse
loss.
● When counting down, if the counter reaches the lower count limit and a further count
pulse comes, it jumps to the upper limit and continues counting from there without any
pulse loss.
Select gate function
In this mode you can select the gate function Options:
● Without gate (default)
● SW gate
● HW gate, level-controlled or edge-controlled
Figure 8-1 Infinite counting with load value and gate function
Open and close SW gate
You open and close the SW gate of the relevant counter with the input parameter SW_GATE
of the FC CNT_CTRL (see chapter "The FC CNT_CTRL function (Page 46)").
Action Initiating event
Open SW gate Set SW_GATE
Close SW gate Reset SW_GATE