CHAPTER 7 INTERRUPT/EXCEPTION PROCESSING FUNCTION
User’s Manual U12688EJ4V0UM00
219
7.3.7 Noise elimination
Digital noise elimination circuits are added to each of the INTPn0 to INTPn3, TIn, TCLRn and ADTRG pins (n = 10
to 15). Using these circuits, these pins’ input level is sampled each sampling clock cycle (f
SMP
). If the same level
cannot be detected 3 times consecutively in the sampling results, that input pulse is removed as noise.
The noise elimination time at each pin is shown below.
Pin
Sampling Clock (f
SMP
)
Noise Elimination Time
TCLR10 to TCLR15
φ
TI10 to TI15
φ
INTP100 to INTP103, INTP110 to INTP113,
INTP120 to INTP123, INTP130 to INTP133,
INTP140 to INTP143, INTP150 to INTP152,
INTP153/ADTRG
φ
2
×
φ
to
3
×
φ
Remark
φ
: Internal system clock
Figure 7-9. Example of Noise Elimination Timing
Sampling
clock (f
SMP
)
Input signal
Internal signal
Rising edge
detection
Falling edge
detection
Max. 3 clocks
Note 1
Min. 2 clocks
Note 2
Notes 1. Pulse width of unrecognizable noise.
2. Pulse width of recognizable signals.
Cautions 1. If the input pulse width is between 2 and 3 sampling clocks, whether the input pulse is
detected as a valid edge or eliminated as a noise is indefinite.
2. To securely detect the level as a pulse, the same level input of 3 sampling clocks or more is
required.
3. When noise is generated in synchronization with a sampling clock, this may not be
recognized as noise. In this case, eliminate the noise by attaching a filter to the input pin.
Содержание V850E/MS1 UPD703100
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