User Manual

Sinusoidal Commutation
Advanced Digital Motor Controller User Manual 113
Digital Absolute Encoder (SSI) Feedback
Some advanced motors, incorporate an absolute position sensor with a high speed serial
interface based on the SSI protocol.
Controllers support SSI encoders with resolution from 12 to 15bits. SSI encoders give the
angle’s absolute position. Nevertheless, a calibration of the zero-angle reference must be
done once in order to capture the mechanical offset of the sensor vs the actual 0 degrees
position.
The SSI’s sensor resolution is set by entering 2 to the power of the number of bits (i.e.
4096, 8192, ...) in the SPI/SSI Sensor Resolution field in the PC utility..
FIGURE 8-20. SPI/SSI Sensor Resolution configuration
Or by sending the configuration command:
^SCPR channel nn
After enabling the Sinusoidal Mode and SSI Angle Feedback, verify first that the SSI
Counter displays a stable number that is different from zero. This will indicate that data is
output from the sensor and captured by the controller. Rotate the motor by hand to verify
that the counter changes.
The 12 to 15 bit raw value of the SSI sensor can be read using the query:
?CSS [channel]
The continuous 32-bit counter and speed that is driven by the SSI sensor can be read us-
ing the following queries respectively:
?CSS [channel]
?SS [channel]
Typically, SPI encoders are single pole sensors, meaning that they output 0 to their maxi-
mum value over a full mechanical turn.
Important Notice
The SSI sensor is used for commutation only. It cannot be used for position mode.
Use single turn sensor only. Multi-turn sensors are not supported.