User’s Manual U11969EJ3V0UM00
119
CHAPTER 5 INTERRUPT/EXCEPTION PROCESSING FUNCTION
5.3.7 Noise elimination
INTP, TI, TCLR, and ADTRG pins are attached with respective digital noise elimination circuit. Thereby, the input
levels of these pins are sampled at each sampling clock (f
SMP
). As a result, if the same level cannot be detected three
times consecutively, the input pulse is eliminated as a noise.
The noise elimination time for each pin is shown below. The sampling clock of INTP30 pin can be selected from
φ
,
φ
/64,
φ
/128, or
φ
/256. For the settings, write values to INTM7 register (refer to 5.3.8 (2) (a) External interrupt
request register 7 (INTM7)).
Pin
f
SMP
Noise Elimination Time
INTP00 to INTP03
φ
2 to 3 system clocks
TCLR0/INTP04
φ
TI0/INTP05
φ
INTP10 to INTP13
φ
TI1/INTP14
φ
TI20/INTP20 to TI24/INTP24
φ
ADTRG
φ
INTP30
φ
2 to 3 system clocks
φ
/64
128 to 192 system clocks
φ
/128
256 to 384 system clocks
φ
/256
512 to 768 system clocks
Remark
f
SMP
: Sampling clock
φ
: Internal system clock
Figure 5-9. Example of Noise Elimination Timing
Notes 1. Unrecognizable noise pulse width
2. Recognizable signal pulse width
f
SMP
Input signal
Internal signal
Rising edge
detected
Falling edge
detected
3 clocks max.
Note 1
2 clocks min.
Note 2
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