Error(21636): QSF assignment PRESERVE_UNUSED_XCVR_CHANNEL has been specified to preserve unused transceiver channels in HSSI IO BANK 9A.

Error(21636): QSF assignment PRESERVE_UNUSED_XCVR_CHANNEL has been specified to preserve unused transceiver channels in HSSI IO BANK 9A. However, no reference clock has been specified using the QSF assignments set_instance_assignment -name HSSI_PARAMETER "refclk_divider_use_as_BTI_clock=TRUE" and set_instance_assignment -name HSSI_PARAMETER "refclk_divider_input_freq=". See E-tile User Guide for more information.

User will meet this error when upgrade design to the Intel® Quartus® Prime Pro Edition software version 20.1 with a global assignment PRESERVE_UNUSED_XCVR_CHANNEL for unused transceiver channels in completely unused tiles.

To preserve all unused channels in completely unused tiles, user need follow the steps below:

1. Add refclk port in top-level design for each tile.
   For example:
       module top (
           input wire refclk_preserve_0,
               ......
           );
2. Add assignments on refclk pin (valid frequency range is 125MHz-500MHz)
   For example:
       set_location_assignment PIN_AT13 -to refclk_preserve_0
       set_instance_assignment -name HSSI_PARAMETER "refclk_divider_use_as_BTI_clock=TRUE" -to refclk_preserve_0
       set_instance_assignment -name HSSI_PARAMETER "refclk_divider_input_freq=156250000" -to refclk_preserve_0
3. Add global assignment to preserve unused channels
   For example:
       set_global_assignment -name PRESERVE_UNUSED_XCVR_CHANNEL ON