NEC mPD703128, Preliminary User'S Manual

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Chapter 10 Timer
Preliminary User’s Manual U15839EE1V0UM00
10.3.9 Edge noise elimination
The edge detection circuit has a noise elimination function. This function regards:
• a pulse not wider than 1 count clock period as a noise, and does not detect it as an edge.
• a pulse not shorter than 2 count clock periods is detected normally as an edge.
• a pulse wider than 1 count clock period but shorter than 2 count clock periods may be
detected as an edge or may be eliminated as noise, depending on the timing.
(This is because the count-up signal of the counter is used for sampling timing.) The upper figure below
shows the timing chart for performing edge detection. The lower figure below shows the timing chart for
not performing edge detection.
Basic settings (x = 0, 1 and y = 0 to 5):
Figure 10-58: Timing of Edge detection noise elimination
Bit Value Remark
CSEx2 0
Count clock = f
PCLK
/4
CSEx1 1
CSEx0 0
IEGy1 1
detection of both edges
IEGy0 1
t+2 t+3 t+4 t+5 t+6 t+7
t+6
t t+1
t+4
t+2 t+4 t+5 t
t+1 t+3
t+6 t+7
<Timing chart for performing edge detection>
<Timing chart for noise elimination>
TMGn0/TMGn1
TIGny
INTCCGny
GCCny
f
PCLK
f
COUNTx
TMGn0/TMGn1
TIGny
INTCCGny
GCCny
f
PCLK
f
COUNTx