2 Basic principles of the counter module
Counter Module SIMATIC FM 350-2
V1.0, Item ID: 83146298
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2.5.4
Periodic counting
In this mode, the counter module performs the following counts:
From the start value 0 to the (end value – 1) in the main count direction "up."
From the assigned start value to the end value (0 + 1) in the main count
direction "down."
If one of the assigned count limits is reached, the counter jumps back to the start
value when the next pulse is received. The counter channel continues to count
from there. For example, if you have assigned the value 100 as an end value for
counting up, the counter module counts to 99 and then jumps to the value 0 when
the next edge occurs.
Figure 2–7: Time diagram for periodic counting, up and down
