SAM3X8E Atmel Corporation, SAM3X8E Datasheet - Page 887

• Manufacturer Part Number: SAM3X8E
• Manufacturer: Atmel Corporation

36.6.14.3
Figure 36-18. Rotation Change Detection
11057A–ATARM–17-Feb-12
11057A–ATARM–17-Feb-12
No direction change due to particulate contamination masking a reflective bar
Direction Change under normal conditions
PHA
PHB
DIR
DIRCHG
PHA
PHB
DIR
DIRCHG
Direction Status and Change Detection
After filtering, the quadrature signals are analyzed to extract the rotation direction and edges of
the 2 quadrature signals detected in order to be counted by timer/counter logic downstream.
The direction status can be directly read at anytime on TC_QISR register. The polarity of the
direction flag status depends on the configuration written in TC_BMR register. INVA, INVB,
INVIDX, SWAP modify the polarity of DIR flag.
Any change in rotation direction is reported on TC_QISR register and can generate an interrupt.
The direction change condition is reported as soon as 2 consecutive edges on a phase signal
have sampled the same value on the other phase signal and there is an edge on the other sig-
nal. The 2 consecutive edges of 1 phase signal sampling the same value on other phase signal
is not sufficient to declare a direction change, for the reason that particulate contamination may
mask one or more reflective bar on the optical or magnetic disk of the sensor. (Refer to
36-18 ”Rotation Change Detection”
The direction change detection is disabled when QDTRANS is set to 1 in TC_BMR. In this case
the DIR flag report must not be used.
missing pulse
spurious change condition (if detected in a simple way)
same phase
change condition
for waveforms.)
Report Time
SAM3X/A
SAM3X/A
Figure
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