Digital Filter; Digital Filter Function Principle; Set Digital Filter Time - Contec DIO-0808L-PCI User Manual

4. Function

Digital Filter

Using this feature, The <DIO-0808L-PCI> can apply a digital filter to every input pin, thereby
preventing the input signal from being affected by noise or chattering.

Digital Filter Function Principle

The digital filter checks the input signal level during the sampling time of the clock signal. When the
signal level remains the same for the digital filter set time, the digital filter recognizes that signal as the
input signal and changes the signal level of the PC
If the signal level changes at a frequency shorter than the set time, therefore, the level change is ignored.
Input Signal
Digital
Filter
Filter Setting Time
Input Signal
Invalid
Input to PC
Figure 4.1. Digital Filter Function Principle

Set Digital Filter Time

Set the digital filter time to 0 - 20 (14h).
Setting the digital filter time to 0 disables digital filtering. It is set to 0 when th e power is turned on.
Figure 4.2 shows the relationships between digital filter time settings and the actual digital filter times.
Digital Filter Time[sec.] = 2
n: = setting data(0 - 20)
Setting Data Digital Filter
(n) Time
0 (00h) The filter function
is not used.
1 (01h) 0.25sec
2 (02h) 0.5sec
3 (03h) 1sec
4 (04h) 2sec
5 (05h) 4sec
6 (06h) 8sec
Figure 4.2. Digital Filter Time and Setting Data
CAUTION
- If you set the digital filter time, the filter applies to all input pins. You cannot apply the filter only to
a specific filter.
- Do not set Setting Data to a value outside the above range as doing so can cause the board to
malfunction.
36
Input to PC
Valid
n 6
/ (8 x 10 )
Setting Data Digital Filter
(n) Time
7 (07h) 16sec
8 (08h) 32sec
9 (09h) 64sec
10 (0Ah) 128sec
11 (0Bh) 256sec
12 (0Ch) 512sec
13 (0Dh) 1.024msec
Setting Data Digital Filter
(n) Time
14 (0Eh) 2.048msec
15 (0Fh) 4.096msec
16 (10h) 8.192msec
17 (11h) 16.384msec
18 (12h) 32.768msec
19 (13h) 65.536msec
20 (14h) 131.072msec
DIO-0808L-PCI