SSI (synchronous serial interface) is a protocol standard based on RS-422 for industrial applications between a master and a slave. It is often used between a controller and a rotary encoder.
SSI2 is a variant of SSI for use with Codechamp encoders.
Speedgoat provide support for the SSI protocol with FPGA code modules. Both differential and single-ended interfaces are supported. Driver blocks for Simulink Real-Time are also provided.