MIPI D-PHY IP User Guide: Agilex™ 5 FPGAs

ID 817561
Date 7/08/2024
Public

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3.5. CSR Clock Domain Crossing (CDC)

There are a few clock domain crossings within the D-PHY soft IP with the most major one being between the regfile’s axi_clk to the rest of the D-PHY PCS.

Most of the control registers from the regfile CSR are not synchronized to the destination clock domains. To ensure proper synchronization, the following sequence should be observed when updating any control registers (this excludes clearing status registers):

  1. Disable D-PHY by writing a 0 to D-PHY_CSR.Enable (offset 0x10 bit 0).
  2. Update control registers.
  3. Enable D-PHY by writing a 1 to D-PHY_CSR.Enable (offset 0x10 bit 0).

An alternative to the above sequence is to use the link’s data lane 0’s PPI.Enable signal to reset the D-PHY link when updating the control registers.