SDAA423 August   2026 AM6411 , AM6412 , AM6421 , AM6422 , AM6441 , AM6442

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2SERDES PLL SSC - Linux SDK Configuration
    1. 2.1 DTS Configuration for SSC
    2. 2.2 DTS Compiling
    3. 2.3 Device Tree Blob (DTB) Copy to SKEVM Boot-Up SD Card
  6. 3Low-Frequency Periodic Signaling (LFPS)
  7. 4CP0 - CP1 Transmission Pattern Setup
  8. 5Summary
  9. 6References

3 Low-Frequency Periodic Signaling (LFPS)

For LFPS tests (shown below), the USB link is initiated as soon as the USB3.0 receiver (RX) detects a 50Ω termination after connecting to the oscilloscope via the USB-IF host test fixture 1. This causes the Port Link State (PLS) of the Port Status and Control (PORTSC) register (0x0F410490) to transition from Rx.Detect (0x0A0002A0) to Polling state (0x0E0002E0). The TX then starts transmitting LFPS bursts continuously. The LFPS pattern is specifically used for the below tests.

  1. LFPS Peak-Peak Differential Output Voltage
  2. LFPS Period
  3. LFPS Burst Width
  4. LFPS Repeat Time Interval
  5. LFPS Rise Time
  6. LFPS Fall Time
  7. LFPS Duty Cycle
  8. LFPS AC Common Mode Voltage

The very low-frequency bursts of about 16.5MHz with bursts happening approximately every 11µ seconds look like the waveforms in the figure below.

LFPS Oscilloscope Waveform LFPS Oscilloscope Waveform Figure 3-1 LFPS Oscilloscope Waveform