User Manual

LOGO! functions
4.4 Special functions list - SF
LOGO!
Manual, 06/2014, A5E33039675
175
Calculation rule
● If the On threshold ≥ Off threshold, then:
Q = 1, if Cnt ≥ On
Q = 0, if Cnt < Off
● If the On threshold < Off threshold, then Q = 1, if On ≤ Cnt < Off.
Note
The system scans the counter limit value cyclically.
Thus, if the pulse frequency at the fast digital inputs I3, I4, I5 or I6 is faster than the cycle
time, the special function might
not switch until after the specified limit value is exceeded.
Example: Up to 100 pulses per cycle can be counted; 900 pulses have been counted so
far. On = 950; Off = 10000. The output is set in the next cycle, after the value has
reached 1000. (The outpu
t would not be set at all if the value Off = 980).
View in programming mode (example):
If the referenced block (B021, in the example) returns a value that lies out of the valid range,
the value is rounded to the next valid value.
The view in parameter assignment mode (example):