This event type is used to detect three types of encoder faults:

  • Broken wire errors
  • Illegal state errors
  • Absolute encoder initialization errors
    • Timeout errors
    • Protocol errors

Broken wire errors are detected for either incremental or absolute encoders whenever both differential inputs of any encoder receiver (A, B, or Index) are at the same voltage level (i. e., whenever one or both inputs is disconnected from the encoders differential transmitter). The EncoderTermination configuration of the encoder input must be TRUE for correct detection of broken wires.

Illegal state errors occur whenever transitions are seen on both A and B phases of an encoder input at the same time (e.g. noise spikes).

There are two types of absolute encoder initialization errors: Timeout errors and Protocol errors.

Timeout errors occur when an absolute encoder does not transmit absolute encoder data within the timeout period starting at the transition of the interrogation line (SEN line).

Protocol errors are detected when serial absolute data is sent during the timeout, but the data cannot be interpreted by the XMP. Both error types result in an ENCODER_FAULT event.

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