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Chapter 3 Interrupts
External Interrupts
■Noise Filter Control Register 0 (NFCTR0)
The noise filter control register (NFCTR0) sets the noise remove function for IRQ0 and IRQ1 and also
selects the sampling cycle of noise remove function. And this register also set the AC zero cross detec-
tion function for IRQ1.
Figure 3-3-4 Noise Filter Control Register 0 (NFCTR0 : x'03F8E', R/W)
NF0SCK1
0
NF0SCK0
0
1
0
1
1
0
1
fosc/2
IRQ0/ noise filter sampling period
fosc
01
24
567
3
( At reset : 0 0 0 0 - 0 0 0 )
NFCTR0
NF0ENNF0SCK0
NF0SCK1
-
NF1EN
NF1SCK0NF1SCK1P21IM
0
1
Noise filter OFF
IRQ0/ noise filter setup
Noise filter ON
NF0EN
0
1
Noise filter OFF
IRQ1/ noise filter setup
Noise filter ON
NF1EN
0
1
Disable ACZ input
ACZ input enable flag
Enable ACZ input
P21IM
8
fosc/2
9
fosc/2
10
NF1SCK1 NF1SCK0
0
1
0
1
fosc/2
IRQ1/ noise filter sampling period
fosc
8
fosc/2
9
fosc/2
10