Remote I/O module 16 DI
AL4042
9
Periodic signals are only detected reliably if the signal period is at least twice as long as the
cycle time.
4.4.1 Debouncing
The filter suppresses noise signals. The filter provides the input signals at the filter output with a delay
(debounce time). All signals shorter than the set debounce time are ignored by the filter.
Time diagram debounce filter:
2
1
1
1
1
0
1
0
1
0
1
t
Process data
Filter output
Filter input
1: Debounce time
2: Cycle time
4.4.2 Stretching
The filter stretches short input pulses. Level changes that occur during a stretching period are ignored.
The filter is configured via the following parameters:
•
Hold time: pulse duration to which short pulses are to be stretched. Pulses that are present for a
longer time than the hold time are not stretched.
•
Hold level: signal level to be stretched (HIGH or LOW)
Time diagram stretch filter (status HIGH):
2
1
1
1
0
1
0
1
0
1
t
Process data
Filter output
Filter input
1: Hold time
2: Cycle time
Time diagram stretch filter (status LOW):
2
1
1
1
0
1
0
1
0
1
t
Filter input
Filter output
Process data
1: Hold time
2: Cycle time
