5: SPECIAL FUNCTIONS
5-24 « FC4A MICROSMART USER’S MANUAL »
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. On the contrary, the input filter rejects short input pulses when the
MicroSmart 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 ms, and 3 through 15 ms in 1-ms increments. Default value is 3 ms
for all inputs I0 through I7. Inputs I10 and above on all-in-one and 20-I/O slim type CPU modules are provided with a
fixed filter of 3 ms. Inputs I10 and above on 40-I/O slim type CPU modules and all expansion input modules have a fixed
filter of 4 ms. The input filter rejects inputs shorter than the selected input filter value minus 2 ms.
Normal inputs require a pulse width of the filter value plus one scan time to receive input signals. When using the input fil-
ter function, select Normal Input on the Special Input page in the Function Area Settings.
Since these settings relate to the user program, the user program must be downloaded to the MicroSmart after changing
any of these settings.
Programming WindLDR
1. From the WindLDR menu bar, select Configure > Function Area Settings. The Function Area Settings dialog box
appears.
2. Select the Others tab.
3. Select an input filter value for each group of inputs.
Input Filter Values and Input Operation
Depending on the selected values, the input filter has three response areas to reject or pass input signals.
Reject area: Input signals do not pass the filter (selected filter value minus 2 ms).
Indefinite area: Input signals may be rejected or passed.
Pass area: Input signals pass the filter (selected filter value).
Example: Input Filter 8 ms
To reject input pulses of 6 ms or less, select input filter
value of 8 ms. Then input pulses of 8 ms plus one scan time
are accepted correctly at the END processing.
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