Atmel SAM4S-EK2 Atmel ATSAM4S-EK2 ATSAM4S-EK2 Data Sheet
Product codes
ATSAM4S-EK2
779
SAM4S [DATASHEET]
11100E–ATARM–24-Jul-13
36.6.14.3Direction 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.
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.
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 signal. 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
value on the other phase signal and there is an edge on the other signal. 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
Figure 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.
not be used.
A quadrature error is also reported by the quadrature decoder logic. Rather than reporting an error only when 2 edges
occur at the same time on PHA and PHB, which is unlikely to occur in real life, there is a report if the time difference
between 2 edges on PHA, PHB is lower than a predefined value. This predefined value is configurable and corresponds
occur at the same time on PHA and PHB, which is unlikely to occur in real life, there is a report if the time difference
between 2 edges on PHA, PHB is lower than a predefined value. This predefined value is configurable and corresponds
PHA
PHB
Direction Change under normal conditions
DIR
DIRCHG
change condition
Report Time
No direction change due to particulate contamination masking a reflective bar
PHA
PHB
DIR
DIRCHG
spurious change condition (if detected in a simple way)
same phase
missing pulse