Contec PI-128L, User Manual, Page: 45 / 62

4. Functions
CONTEC CO., LTD.
38
PIO-64/64L(PCI), PI-128L(PCI), PO-128L(PCI)
Digital Filter Function of Input Channels
<PIO-64/64L(PCI)>, <PI-128L(PCI)> are equipped with a digital filter function for input signals. This
function provides all input channels with a means of cutting chattering and noise.
Digital Filter Function Principle
To use this function, you must set a filter time. The function circuits will then check all input signals
synchronizing with the clock. A signal level, low or high, will be input only if the signal level remains
stable during the filter set time. Therefore, if a signal level changes faster than the filter set time, this
level change will be ignored and the previous signal level will be input.
Input S ig nal
Filter Se ttin g Tim e
Inv alid
Valid
Inpu t to PC
Input S ig nal
D ig ital
Filter
Input to P C
Figure 4.1. Digital Filter Function Principle
Set Digital Filter Time
Set the digital filter time to 0 to 24 (14h).
Setting the digital filter time to 0 disables digital filtering. It is set to 0 when the power is turned on.
Table 4.1. shows the relationships between digital filter time settings and the actual digital filter times.
Digital Filter Time[sec.] = 2
n
/ (8
´
10
6
)
n: = setting data(0 to 20)
Table 4.1. Digital Filter Time and Setting Data
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
CAUTION
- Writing a setting data other than a "0" will apply this filter function to all input channels. This
function cannot be applied to particular pins only but is applied to all input channels.
- Do not set a data more than 20(14H). Doing so may cause the board malfunctioning.