What is Serial Synchronous Interface (SSI)

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What is Serial Synchronous Interface (SSI)?
Hardware: Multifunction DAQ (MIO)

Problem:
What is Serial Synchronous Interface (SSI)?
Solution:
SSI (Serial Synchronous Interface) is a widely used serial interface between an absolute position sensor and a controller. SSI uses a clock pulse train from a controller to initiate a gated output from the sensor.
Position data is continually updated by the sensor and made available to the shift register. Between each clock pulse train there is a minimum dwell of 25 microseconds during which fresh data is moved into the register. Data is shifted out when the sensor receives a pulse train from the controller. When the least significant bit (LSB) goes HIGH and the minimum dwell time has elapsed, new data is available to read. Refer to the diagrams below.
Synchronous Mode: A synchronous pulse from the control system starts the measuring time of the sensor, the measured result is available before the next synchronizing pulse is generated. The synchronizing pulse is the first high to low transition of the clock train after the dwell time.
Asynchronous Mode: SSI takes measurements at its fastest internal interrogation rate (length dependent) and provides information upon request.
SSI Block Diagram

SSI Timing Diagram

Sequential measurements of SSI Timing


Baud Rates For Data TransmissionCable Length (ft.)
Baud Rate*
*Maximum baud rate: 1.5 MBaud
Related Links:
Developer Zone Community: LV FPGA SSI (Synchronous Serial Interface) Protocol
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