Finding home

The encoders that the ZY is equipped with are incremental encoders. They do not remember where they were when power is removed from the encoders, or when the LM628 is reset. In this situation the encoders are useless in pointing a laser beam to a target. Fortunately, the encoder is equipped with an index position, which produces a pulse when the encoder travels through it. The LM628 can be instructed to record the position register reading when this index pulse and both of the encoder-phase inputs are logic low. The LM628 can then be instructed to return to this position and define this position as home, or position `0'. This process is referred to as finding home (see figure2.5).

Figure 2.5: ZY Servo Find Home Flowchart.