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CHAPTER 7 INTERRUPT/EXCEPTION PROCESSING FUNCTION
User’s Manual U15109EJ3V0UD
239
(3) Elimination of noise from INTP6 pin
A digital noise eliminator is provided on chip. The sampling clock for digital sampling can be selected from
among f
XX
, f
XX
/64, f
XX
/128, f
XX
/256, f
XX
/512, f
XX
/1024, and f
XT
. Sampling is performed 3 times.
The noise elimination control register (NCC) selects the clock to be used. Remote control signals can be
received effectively with this function.
f
XT
can be used for the noise elimination clock. In this case, the INTP6 external interrupt function is enabled in
the IDLE/STOP mode.
This register can be read/written in 8- or 1-bit units.
Caution
After the sampling clock has been changed, it takes 3 sampling clocks to initialize the noise
eliminator. For that reason, if an INTP6 valid edge is input within these 3 clocks, an interrupt
request may occur. Therefore, observe the following points when using the interrupt and DMA
functions.
••••
When using the interrupt function, after 3 sampling clocks have elapsed, enable interrupts
after the interrupt request flag (bit 7 of PIC6) has been cleared.
••••
When using the DMA function, after 3 sampling clocks have elapsed, enable DMA by setting
bit 0 of DCHCn.
(a) Noise elimination control register (NCC)
After reset: 00H
R/W
Address: FFFFF3D4H
7
6
5
4
3
2
1
0
NCC
0
0
0
0
0
NCS2
NCS1
NCS0
Reliably eliminated noise width
Note
NCS2
NCS1
NCS0
Sampling clock
f
XX
= 20 MHz
f
XX
= 18.87 MHz
f
XX
= 16 MHz
0
0
0
f
XX
100.0 ns
105.0 ns
125.0 ns
0
0
1
f
XX
/64
6.4
µ
s
6.7
µ
s
8.0
µ
s
0
1
0
f
XX
/128
12.8
µ
s
13.5
µ
s
16.0
µ
s
0
1
1
f
XX
/256
25.6
µ
s
27.1
µ
s
32.0
µ
s
1
0
0
f
XX
/512
51.2
µ
s
54.2
µ
s
64.0
µ
s
1
0
1
f
XX
/1024
102.4
µ
s
108.5
µ
s
128.0
µ
s
1
1
0
Setting prohibited
1
1
1
f
XT
61
µ
s
Note
Since sampling is performed three times, the reliably eliminated noise width is 2
×
sampling clock.