6850 - Diamond: ERROR - Based on the current IO attributes settings, port xxxxx cannot be assigned to pin [xx].

6850 - Diamond: ERROR - Based on the current IO attributes settings, port xxxxx cannot be assigned to pin [xx].

Description:

This article explains an error in Diamond which reports the port cannot be assigned to certain pin during synthesis due to the pin assignment done via constraint.

Solution:

This error in Diamond is caused by optimization done during synthesis which disconnects the signal/net from the whole design, and then causes Place & Route (PAR) issue.

Here is a scenario of how this error happens:
1. In RTL netlist view, the sample signal TFT_G has connection to HDMI_GRN_mix:

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