SmartAXIS Touch User's Manual 3-79
4 Special Functions
3
Project
4.11 Input Filter
The input filter function is used to reject input noises. The catch input function described in the preceding section is
used to read short input pulses to special internal relays.
● Feature Description
The input filter rejects short input pulses when the Touch is used with input signals containing noises.
Different input filter values can be selected for inputs I0 through I7 in four groups using the Function Area Settings.
Selectable input filter values to pass input signals are 0 millisecond, and 3 through 15 milliseconds in 1 millisecond
increments. Default value is 3 milliseconds for all inputs I0 through I7. Inputs I10 and above on Touch are provided
with a fixed filter of 3 milliseconds.
Input Filter Values and Input Operation
Depending on the selected values, the input filter has three response areas to reject or pass input signals.
The input filter rejects inputs shorter than the selected input filter value minus 2 milliseconds.
Example: Input Filter
To reject input pulses of 6 milliseconds or less, select input filter value of 8 milliseconds. Then input pulses of 8
milliseconds plus one scan time are accepted correctly at the END processing.
• Input signals : Input signals do not pass the filter (selected filter value minus 2 milliseconds).
• Pass area : Input signals pass the filter (selected filter value).
• Indefinite area : Input signals may be rejected or passed.
6 msec 8 msec
Rejected Indefinite Accepted
• Signals that pass through input filters are not necessarily captured as inputs. Normal inputs require a
pulse width of the filter value plus one scan time to receive input signals.
• If external inputs are set as high-speed counters, interrupt inputs, frequency measurement, or analog
inputs, input filters are disabled.
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