WAGO I/O SYSTEM 750 Series Manual

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750-631(750-631/000-001) [Incremental Encoder Interface] • 17Functional DescriptionWAGO-I/O-SYSTEM 750I/O Modules2.1.2.7 Functional DescriptionThe incremental encoder interface is used to evaluate two 90° phase-shiftedtrack signals delivered by digital encoders. If required, the signals generatedby the index track can also be processed. Control via two 24 V signals isoptional.Typically, incremental encoders provide two signals of the encoder track, both90° offset. These signals are labeled A and B. To improve the common moderejection ratio, both signals are transmitted as differential signals. In additionto the A signal, the complement signal /A is also transmitted. The differencebetween the input signals is performed by the incremental encoder interface.By exchanging A and /A the phase position will turn from A to B, thusallowing the desired counting direction to be preset via the wiringconfiguration.Most incremental encoders have an index track in addition to the two tracksignals. This index track generates a single pulse per encoder revolution. Thispulse can be used to determine the absolute encoder position within arevolution. Through the appropriate initialization, the current counter value istransmitted to a latch register using the index pulse. Since the index pulse hasthe same duration as a track signal, the latch process should always beperformed in the same rotational direction.The encoder is supplied with 5 V derived from the terminations Ue and U0.This voltage is generated from an external 24 V power supply. The inputs 0 Vand U0 are connected internally.The latch input controls the overtaking of the actual counter value into thelatch register. This input is activated by the control bit EN_LATEXT (”1“).EN_LACT has to be deactivated (“0“). After activation, the first edge transi-tion from 0 V to 24 V at the latch input takes the actual counter value into thelatch register. The control bit EN_LATEXT must be deleted and reset, so thatthe counter value can be stored again.The gate input stops the counter. Only 0 V or and open connection initializethe counter. 24 V stops the counting process.The latch and gate inputs are 24 V.