Contec PI-128L(PCI)H, Руководство пользователя

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4. Functions
46
PIO-64/64L(PCI)H, PI-128L(PCI)H, PO-128L(PCI)H
Digital Filter Function
Using this feature, the < PIO-64/64L(PCI)H > and < PI-128L(PCI)H > can apply a digital filter to
every input pin, thereby preventing wrong recognition of input signals 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.
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 the power is turned on.
Figure 4.2 shows the relationships between the digital filter time and the setting data.
Digital Filter Time[sec.] = 2
n
/ (8 x 10
6
)
n: = setting data(0 - 20)
Setting Data
(n)
Digital Filter
Time
Setting Data
(n)
Digital Filter
Time
Setting Data
(n)
Digital Filter
Time
0 (00h) The filter function
is not used.
7 (07h) 16 µ sec 14 (0Eh) 2.048msec
1 (01h)
0.25
µ
sec
8 (08h)
32
µ
sec
15 (0Fh) 4.096msec
2 (02h)
0.5
µ
sec
9 (09h)
64
µ
sec
16 (10h) 8.192msec
3 (03h) 1 µ sec 10 (0Ah) 128 µ sec 17 (11h) 16.384msec
4 (04h) 2 µ sec 11 (0Bh) 256 µ sec 18 (12h) 32.768msec
5 (05h)
4
µ
sec
12 (0Ch)
512
µ
sec
19 (13h) 65.536msec
6 (06h)
8
µ
sec
13 (0Dh) 1.024msec 20 (14h) 131.072msec
Figure 4.2. Digital Filter Time and Setting Data
- If you set the digital filter time, the filter applies to all input pins. You cannot apply the filter only
to a specific input pin.
- Do not set a value outside the above range to the Setting Data as doing so can cause the board to
malfunction.
Input Signal
Filter Setting Time
Invalid
Valid
Input to PC
Input Signal
Digital
Filter
Input to PC
CAUTION