Noise Filter - Panasonic F77G User Manual

3-3-7

Noise Filter

Noise Filter (External interrupts 0 to1)
Noise filter reduce noise by sampling the input waveform from the external interrupt pins (IRQ0, IRQ1).
Its sampling cycle can be selected from 4 types (fosc, fosc/2
Noise Remove Selection (External interrupts 2 to 4)
Noise filter reduce noise by sampling the input waveform from the external interrupt pins (IRQ2 to IRQ4). Its
sampling cycle is fosc.
Noise Remove Selection (External interrupts 0 to 4)
Noise remove function can be selected by setting the NFnEN flag of the noise filter control register
(NFCTR) to "1".
NFnEN
IRQ0 input (P20)
IRQ1 input (P21)
IRQ2 input (P22)
IRQ3 input (P23)
IRQ4 input (P24)
Sampling Cycle Setup (External interrupts 0 and 1)
The sampling cycle of noise remove function can be set by the NFnSCK 1- 0 flag of the NFCTR register.
Table 3-3-4
NFnCKS1
0
1
Table 3-3-3
IRQ0 Noise filter OFF
IRQ1 Noise filter OFF
IRQ2 Noise filter OFF
IRQ3 Noise filter OFF
IRQ4 Noise filter OFF
Sampling Cycle / Time of Noise Remove Function
Sampling
NFnCKS0
cycle
0 fosc
8
1
fosc/2
9
0
fosc/2
10
1
fosc/2
8 , fosc/2
Noise Remove Function
0
High-Speed oscillation
fosc=20 MHz
20 MHz 50 ns
78.13 kHz 12.80 s
39.06 kHz 25.60 s
19.53 kHz 51.20 s
Chapter 3 Interrupts
9 , fosc/2 10 ).
1
IRQ0 Noise filter ON
IRQ1 Noise filter ON
IRQ2 Noise filter ON
IRQ3 Noise filter ON
IRQ4 Noise filter ON
fosc=8 MHz
8 MHz 125 ns
31.25 kHz 32 s
15.62 kHz 64 s
7.81 kHz 128 s
External Interrupts
III - 51