The SSI daughter board provides the interface to a DC or Brushless servo motor fitted with an absolute SSI Gray Code encoder or encoder emulation. The encoder port provides high speed differential synchronous serial interface (SSI). This port is opto-isolated to maximise the noise immunity of the system.

 

The SSI port is programmable so that any number of bits from 1 to 24 can be clocked into the position registers. If the registration function is to be used then a minimum of 12 bits is required for correct operation.

 

 The SSI daughter board provides a hardware position capture function for both a 5V differential input and a dedicated 24Volt registration input. Transitions of either polarity on both these inputs can be used to record the position of the axis at the time of the event within less than 1 micro seconds. This practically eliminates time delays and avoids interrupting the processor frequently in multi-axis systems. It should be noted however that the SSI system overall does not support this level of accuracy due to delays in clocking data from the encoders. The servo daughter board provides a 12 bit +/-10V voltage output to drive most servo-amplifiers. The voltage output is opto-isolated as standard to maximise the noise immunity of the system.