HEIDENHAIN PWM 8 - Manual (Page 53)

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12.1.3 Output Signals
TTL
TTL square-wave signals
Encoders that output TTL square-wave signals feature electronics that digitize the sinusoidal scanning
signals without interpolation.
Two TTL square-wave signals Ua1 and Ua2 that are phase-shifted by 90° are output together with the
reference pulse Ua0 gated with the incremental signals Ua1 and Ua2. Encoders with distance-coded
reference marks output several Ua0 reference pulses.
The measuring step results from the distance between two edges of the signals Ua1 and Ua2.
To each square-wave signal the integral electronics in addition outputs the corresponding inverted signal.
Incremental signals
TTL square-wave signal trains Ua1, Ua2 and their inverted
signal trains Ua1 and Ua2 .
Ua2 lags Ua1 with ccw rotation (view on shaft or on encoder
flange) or when the scanning unit moves away from the ID plate -
of the linear encoder.
Edge separation a
≥
0.4 µs at 400 kHz scanning frequency
a
≥
0.45 µs at 300 kHz scanning frequency
a
≥
0.8 µs at 160 kHz scanning frequency
a
≥
1.3 µs at 100 kHz scanning frequency
The scanning frequency depends on the encoder model.
Reference mark signal 1 square-wave pulse Ua0 and its inverted pulse Ua0
Pulse width 90° elec.
Delay time Itdl
≤
50 ns
Fault detection signal 1 square-wave pulse UaS
(single-ended signal: max. cable length 50m)
UaS = LOW: fault detected
UaS = HIGH: device operates properly