Some serial NOR flash vendors reach larger densities by stacking die in the same package. For use with UltraScale architecture-based FPGAs, these types of devices must offer a transparent interface and read behavior to the FPGA. UltraScale architecture-based FPGAs do not support single flash devices that use multiple select pins. UltraScale FPGAs also issue a single SPI read command to read in an entire bitstream. If a flash does not read seamlessly with a single command across any die boundaries, it cannot be used to store a configuration bitstream if the bitstream crosses the die boundary.