Rievtech xLogic ELC Series User Manual page 108

The on threshold On and the off threshold Off can be provided by the value of another
already-programmed function:
Analog comparator: Ax – Ay
Analog trigger: Ax
Analog amplifier: Ax
Analog multiplexer: AQ
Analog ramp: AQ
Analog math: AQ
PI controller: AQ
Data latching relay: AQ
Up/Down counter: Cnt
The value of ＂On＂，＂Off＂and ＂Cnt＂can be set/modified in parameter mode. For information about
how to modify ,refer to chapter 5.2.2 please.
Timing diagram
Description of the function
The function increments (Dir = 0) or decrements (Dir = 1) the internal counter by one count with every
positive edge at input Cnt.
You can reset the internal counter value to '000000', with a signal at the reset input R. As long as R=1,
the output is 0 and the pulses at input Cnt are not counted.
Output Q is set and reset according to the actual value at Cnt and the set thresholds. See the following
rules for calculation.
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.
Caution
The function polls the limit value of the counter once in each cycle.
Thus, if the pulses at the fast inputs are faster than the scan cycle time, the SFB might not switch until
the so specified limit has been 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 output would not be set at all if the value Off = 980
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