8.7.6.16.9 Report of Filtered Pulses due to Contamination/Dust

When the digital filter removes pulses created by contamination/dust, a report is provided in the TC QDEC Interrupt Status Register. A separate flag is provided for each line (PHA, PHB, Index) and one flag is provided when a missing pulse is corrected (a ‘1’ must be written to TC_BMR.AUTOC). If TC_QISR.FPHA=1, a pulse has been filtered on PHA line. If TC_QISR.FPHB=1, a pulse has been filtered on PHB line. If TC_QISR.FIDX=1, a pulse has been filtered on Index line. If TC_QISR.FMP=1, a missing pulse has been corrected by the missing pulse detection logic.

The on-the-fly detection and associated flags can be used to anticipate further effects of contamination/dust, in particular if the flag is written to ‘1’ when the rotary encoder speed is high. This may cause abnormal behavior when the rotary encoder slows down if the abnormal pulse is no longer filtered (surpassing digital filter capabilities).

This detection circuitry does not prevent rotary encoder integrity check before use.