In the 7 Series FPGAs Configuration User Guide v1.4 (UG470), there is a note indicating that fallback will not work with the 32-bit addressing mode:
"The MultiBoot and fallback feature can be used with all master configuration modes, except when the 32-bit addressing option is used with the master SPI configuration mode."
How can I work around this issue to use MultiBoot and Fallback on a SPI flash of 256 Mb or larger?
A fix has been implemented in ISE Design Suite BitGen 14.4 and Vivado write_bistream 2012.4. This enables fallback to work correctly with a 256 Mb or larger flash and 32-bit addressing mode.
The 7 Series FPGAs Configuration User Guide (UG470) has been updated.