DisplayPort Intel® Stratix® 10 FPGA IP Design Example User Guide

ID 683887
Date 1/07/2022

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2.8. DisplayPort Transceiver Reconfiguration Flow

The VESA DisplayPort Standard version 2.0 supports 5 link rates (10 Gbps, 8.1 Gbps, 5.4 Gbps, 2.7 Gbps, and 1.62 Gbps). You can dynamically switch from 1 data rate to another. Transceiver reconfiguration is required to support dynamic link rate switching.

The DisplayPort Intel® FPGA IP design examples require some level of reconfiguration and recalibration but with some modification. In these design examples, the pre-calibration method is implemented to reduce the transceiver reconfiguration duration.

Figure 10. Transceiver Reconfiguration Flowchart
The following sequences describe the flow.
  1. Upon power up or push button reset, the DisplayPort reconfiguration module initiates the transceiver reconfiguration to sweep across all supported link rate and all lane count.
    1. For TX FPLL, these register offsets are reconfigured:
      • 11’h12B (TXPLL M Counter)
      • 11’h12C (TXPLL L Counter)
    2. For RX CDR, these register offsets are reconfigured:
      • 11’h13a (RX L PFD and PD Counter)
      • 11’h13b (RX M Counter)
  2. After reconfiguration completes, recalibration initiates per data rate.
  3. After calibration completes, the pre-defined calibrated registers will be stored according to the respective data rate.
    1. For TX FPLL, these register offsets are recalibrated:
      • 11’h10A (PLL VCO Frequency Band 0 fix low bits)
      • 11’h123 (PLL VCO Frequency Band 1 fix)
      • 11’h133
      • 11’h136
    2. For RX CDR, these register offsets are recalibrated:
      • 11’h132 (CDR VCO Speed fix)
      • 11’h133 (Charge Pump Vcc register)
      • 11’h135 (LF PFD and PD Register)
      • 11’h136 (CDR VCO Speed fix)
      • 11’h137 (CDR VCO Speed fix)
      • 11’h139 (Charge Pump current PFD and PD register)
  4. Steps 1 through 3 are repeated until all supported data rates are covered.
  5. When the pre-calibration steps complete, the reconfiguration module is ready to start DisplayPort link training.
  6. Whenever the DisplayPort Intel® FPGA IP sends a new link rate request, the reconfiguration module initiates reconfiguration to the transceiver.
  7. The reconfiguration flow includes retrieving the calibrated register offset value that corresponds to the link rate and reconfigure it to the transceiver. No recalibration is required.
  8. When reconfiguration completes, the transceiver is ready to receive the link rate.
  9. The DisplayPort reconfiguration module continues to monitor if a new link rate request is detected. If it detects a new request, the module repeats step 5.

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