When I attempt to add a PROM file to target an SPI/BPI flash attached to an automotive Spartan-3A Flash device, I see the following message:
ERROR:iMPACT - The assigned file exceeds the capacity of the largest flash device supported for indirect flash programming using iMPACT.
How do I program this attached flash?
To work around this issue you need to assign a non automotive bit file or BSDL file to the Spartan-3A device. Once you do this iMPACT should recognize the PROM file as correct and will not issue this error.