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TM4C123AH6PM: What happen when phA and phB of EQI change simultaneously

Part Number: TM4C123AH6PM

Hi Experts,

Due to the noise environment, there is a chance that phA and phB of QEI module input signals rise or fall simultaneously. In this case, what happens on QEI counter? Is it incremented or decremented? 

I was looking for any logic table for phA/phB and timing figure but could not find it on the datasheet.



  • Hi Uchikoshi-san,

      I think this is a hypothetical question. If that phA and phB rise and fall simultaneously, then QEI can mis-interpret for either direction resulting with an error. The error will be captured in the QEISAT register. 

    Please also note that the QEI is based on two-bit gray code inputs.