CHAPTER 17 INTERRUPT/EXCEPTION PROCESSING FUNCTION
User’s Manual U16896EJ2V0UD
555
<Noise elimination width>
The digital noise elimination width (t
WIT3
) is as follows, where T is the sampling clock period and M is the
number of samplings.
•
t
WIT3
< (M
−
1)T:
Accurately eliminated as noise
•
(M
−
1)T
≤
t
WIT3
< MT: May be eliminated as noise or detected as valid edge
•
t
WIT3
≥
MT:
Accurately detected as valid edge
To detect the valid edge input to the INTP3 pin accurately, therefore, a pulse wider than MT must be input.
Minimum Elimination Noise Width
NFSTS NFC2 NFC1 NFC0 Sampling
Clock
f
XX
= 20 MHz
f
XX
= 10 MHz
f
XX
= 8 MHz
0 0 0 0
f
XX
/64 6.4
μ
s 12.8
μ
s 16
μ
s
0 0 0 1
f
XX
/128 12.8
μ
s 25.6
μ
s 32
μ
s
0 0 1 0
f
XX
/256 25.6
μ
s 51.2
μ
s 64
μ
s
0 0 1 1
f
XX
/512 51.2
μ
s 102.4
μ
s 128
μ
s
0 1 0 0
f
XX
/1024 102.4
μ
s 204.8
μ
s 256
μ
s
0 1 0 1
f
XT
(32.768 kHz)
61.04
μ
s
1 0 0 0
f
XX
/64 3.2
μ
s 6.4
μ
s 8
μ
s
1 0 0 1
f
XX
/128 6.4
μ
s 12.8
μ
s 16
μ
s
1 0 1 0
f
XX
/256 12.8
μ
s 25.6
μ
s 32
μ
s
1 0 1 1
f
XX
/512 25.6
μ
s 51.2
μ
s 64
μ
s
1 1 0 0
f
XX
/1024 51.2
μ
s 102.4
μ
s 128
μ
s
1 1 0 1
f
XT
(32.768 kHz)
30.52
μ
s
Other than above
Setting prohibited
17.4.2 Edge detection
The valid edges of the NMI and INTP0 to INTP7 pins can be selected from the following four types for each pin.
•
Rising edge
•
Falling edge
•
Both edges
•
No edge detection
After reset, the edge detection for the NMI pin is set to “no edge detection”. Therefore, interrupt requests cannot
be acknowledged (the NMI pin functions as a normal port) unless a valid edge is specified by the INTR0 and INTF0
registers.
When using the P02 pin as an output port, set the NMI pin valid edge to “no edge detection”.
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