The Enable STARTUPEn Primitive parameter is applicable in master SPI mode. When this parameter is enabled, the STARTUPE2 primitive (for 7 series) and STARTUPE3 primitive (for AMD UltraScale™ devices) are included in the design and become part of the core after configuration of the FPGA.
See the answer records or the device user guide to understand more about the functionality and use of the STARTUPEn primitive.