Why is the HDMI 2.1 Character Error Detection (CED) register always full when read from an external source?

Due to a problem in the HDMI Intel® FPGA IP, when an external source reads the HDMI 2.1 RX CED register via the SCDC transaction, the error counter shown will appear to be always full (7FFFh) regardless of the actual character error count.

This problem impacts the Intel® Quartus® Prime Pro Edition Software version 21.1 onwards.

A patch is available to fix this problem for the Intel® Quartus® Prime Pro Edition Software version 21.3.

Download and install Patch 0.51 from the following links:

• Intel® Quartus® Prime Pro Edition version 21.3 Patch 0.51 for Windows (.exe)
• Intel® Quartus® Prime Pro Edition version 21.3 Patch 0.51 for Linux (.run)
• Readme for Intel® Quartus® Prime Pro Edition version 21.3 Patch 0.51 (.txt)

This problem has been fixed starting in the Intel® Quartus® Prime Pro Edition Software version 22.4.