4. Function
54
DIO-6464L-PE, DI-128L-PE, DO-128L-PE
Digital Filter Function
Using this feature, the < DIO-6464L-PE > and < DI-128L-PE > 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.
Input Signal
Filter Setting Time
Invalid
Valid
Input to PC
Input Signal
Digital
Filter
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 the 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
/ (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
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.