Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

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SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

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 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

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.

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

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