TTL square-wave signals

HEIDENHAIN encoders with TTL  interface incorporate electronics that  digitize sinusoidal scanning signals withnor without interpolation.

The incremental signals are transmitted as the square-wave pulse trains Ua1 and Ua2, phase-shifted by 90° elec. The reference mark signal consists of one or more reference pulses Ua0, which are gated with the incremental signals. In addition, the integrated electronics produce their inverted signals Ua1^(Inverted) and Ua2^(Inverted) and Ua0^(Inverted)  for noise-proof transmission. The illustrated sequence of output signals—with Ua2 lagging Ua1—applies to the direction of motion shown in the dimension drawing.

 The fault-detection signal UaS^(Inverted)  indicates fault conditions such as breakage of the power line or failure of the light source. It can be used for such purposes as machine shut-off during automated production. The distance between two successive edges of the incremental signals Ua1 and Ua2 through 1-fold, 2-fold or 4-foldevaluation is one measuring step. The subsequent electronics must be designed to detect each edge of the square-wave pulse. The minimum edge separation a stated in the Specifications applies for the specified input circuit with a cable length of 1 m and refers to a measurement at the output of the differential line receiver.

 Note; Not all encoders output a reference mark signal, fault-detection signal, or their inverted signals. Please see the connector layout for this.