53.6.2.6.1 Position and Rotation Measurement

After filtering, the quadrature signals are analyzed to extract the rotation direction and edges in order to be counted by the counter.

The counter is split in two parts, Angular and Revolution. The Phase A and B edge detections define the motor axis position, which is recorded by the Angular part of the counter. The motor revolution is recorded by the Revolution part of the counter. The Angular counter is updated each time a QDEC transition is detected. The Revolution counter is updated on each angular counter overflow or underflow.

in Q4 and Q4S configuration, a valid index is detected when the three inputs (PhaseA, PhaseB and Index) are at low level.

In Q2 and Q2S configuration, a valid index is detected when the two inputs (Count and Index) are at low level.

in Q2 and Q4 configuration, depending on current detected direction, Index will reset or reload the Angular counter and increment or decrement the Revolution counter.

In Q2S and Q4S configuration, the Angular counter is reset on the first Index occurrence after the PDEC decoding is enabled. When any next Index occurrence does not match an Angular counter overflow or underflow, the Index Error flag in Status register is set (STATUS.IDXERR). The Error Interrupt Flag is set (INTFLAG.ERR) and an optional interrupt can be generated.

An Index Error is also generated after the PDEC decoding is enabled and no Index has been detected after one Angular counter revolution.