Datasheet

P(n)
P(n+1)
HET[2]
ext. ref.
signal
APCNT
period
counter
SCNT
step
counter
ACNT
angle
generator
Deceleration Acceleration
ACF
Acceleration
K-1
0 1 2
0 1
2 0 1
flag
DCF
Deceleration
flag
K-1
N1=N0+nK-P(n-1)
N1+K
N1+2K
Final Count = N1+mKFinal Count = N0+nK
E
E
N2=N1+mK-P(n-1)
Target=P(n-1)
SCNT
step
counter
N0
N0+K
N0+2K
N0+3K
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Angle Functions
Figure 23-31. SCNT Count Operation
ACNT detects period variations of the external signal measured by APCNT and compensates related
counting errors. A period increase is flagged in the deceleration flag. A period decrease is flagged in the
acceleration flag. If no variation is flagged, ACNT increments the counter value each time SCNT reaches
its target. If acceleration is detected, ACNT increments the counter value on each timer resolution (fast
mode). If deceleration is detected, ACNT is stopped. Figure 23-32 illustrates how the compensations for
acceleration and deceleration operate.
Figure 23-32. ACNT Period Variation Compensations
23.3.1.1 Singularities
Singularities (gaps, in this case, from missing teeth in a toothed wheel) in the external reference signal
can be masked. The start and end of singularities are defined by gap start and gap end values specified in
SCNT and ACNT. When ACNT reaches gap start or gap end, it sets/resets the gap flag.
While the gap flag is set, new periods of the external reference signal are ignored for angle computation.
SCNT uses the last period measured by APCNT just before gap start.
965
SPNU562May 2014 High-End Timer (N2HET) Module
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