Connect to Digital Quadrature Encoders

Encoder Wiring

Note

The 100 ohm terminations to the receivers are software-selectable. If you use the Scale Interpolation Module (SIM), you must program the 100 ohm terminations off, i.e., remove them from the circuit. To learn more about encoder termination, please refer to Application Note 206.

Connect to Differential Encoders

Connect to differential encoders (digital).

Connect to Single-ended Encoders

Note	To connect the XMP's differential line receivers to single-ended encoders, you must add a pair of resistors (R1, R2) in the configuration shown, to bias the negative end to the middle of the encoder's output voltage range.

Connect to single-ended encoders (digital).

Broken Wire and Illegal State Detection

The encoder inputs (channel A+, A-, B+, B-) are monitored by the FPGA (an on-board logic component). The encoder inputs are sampled at 20mHz. By default, a digital filter is applied to each encoder input. This digital filter requires that an encoder input (channel A+, A-, B+, B-) be stable for 4 clock cycles (200 nanoseconds) before a transition is recognized, i.e., encoder input states lasting less than 4 clock cycles are filtered out.