SSI error bit – critical

What does F14.20 mean?

A critical error bit has been set within the SSI protocol from Encoder 2, indicating a severe communication or data integrity issue. This can be due to incorrect parameters, encoder settings, wiring faults, or external interference, leading to unreliable or lost position data.

• Incorrect SSI clock frequency (P3-54) configured in the drive for Encoder 2, mismatching the encoder's specification.
• Data corruption on the SSI data line due to severe electromagnetic interference (EMI) or inadequate cable shielding (e.g., shield grounded only at one end).
• Internal failure of Encoder 2, leading to intermittent or continuously incorrect SSI data output, including critical error flags.
• An intermittent open circuit or short circuit within the SSI data or clock lines (DATA+, DATA-, CLOCK+, CLOCK-) of Encoder 2 cable.

Click steps to track your progress.

1. 1

   Verify drive parameter P3-54 (SSI clock frequency for Encoder 2) matches the technical specifications of Encoder 2.

2. 2

   Inspect the entire length of the Encoder 2 cable for mechanical damage or improper shielding connections (e.g., ensure shield is properly terminated at both ends, if required).

3. 3

   Using an oscilloscope, capture and analyze the SSI clock and data signals (CLOCK+/-, DATA+/-) at drive terminal X2 for signal integrity and noise.

4. 4

   Measure the voltage supply to Encoder 2 at the encoder connection points (e.g., +24V to 0V) to ensure it is within specified limits.

5. 5

   Temporarily replace Encoder 2 with a new or known-good encoder unit to determine if the fault is encoder-specific.