Warning while assembling the USB to Serial reference design firmware

Question: A Warning is received while assembling the USB to Serial reference design firmware. What is cause of this warning?

 

Answer:

The warning received is:

Page crossing detected and XPAGEOFF enabled.
2034.45:     jmp     Get_Interface                   ;


This warning doesn't cause any harm in this particular case. The reason is that the firmware does not start the Jump_Table at the beginning of a page, so when you try to go across the page boundary with XPAGEOFF, you'll get this warning (please see the XPAGEON, XPAGEOFF directives in the Cyasm User's Guide for detailed discussions on this).

To avoid the warning, place the "ORG F00h" instruction right above the Jump_Table to start the tables on the last page of the 4K ROM).