The counter error includes abnormal input error (AI), digital filter error (FE) and disconnection alarm error (ALM).
Abnormal input error
The abnormal input error is the case when A-phase and B-phase changed at the same time.
Digital filter error
The digital filter error occurs when high-speed signal (A phase, B phase) input is faster than digital filter setting.
Disconnection alarm error
The disconnection alarm error is the case of detecting disconnection for line receiver input. It is only valid when the terminal resistor has been set to ON.