SSI

The Synchronous Serial Interface (SSI) is a digital interface for absolute position and angle measurement systems. It enables position or angle information to be transmitted digitally, in absolute terms, and without protocol overhead. It is therefore particularly suitable for dynamic applications where reliability and signal robustness are required in industrial environments.
Transmission occurs synchronously with the controller’s request; with each clock pulse, one bit of the position value to be output is transmitted. The clock and data signals are transmitted differentially via an RS422 interface.

The data formats are binary or Gray-coded with a 24- or 25-bit position resolution. A parity bit can also be appended to the data format to increase data reliability (SSI26). Possible clock frequencies range from 60 kHz to 2 MHz, and update rates of up to 16 kHz can be achieved. The maximum achievable clock frequency depends on the cable length and the driver components used. The SSI interface is thus a reliable, dynamic, and cost-effective interface.