The Enable Dual Quad Mode parameter is applicable only (UltraScale™ and future devices) in following configuration of the IP core.
•SPI mode is QUAD
•Number of slaves is 2
When this parameter is enabled, the IP core has two SPI interfaces. IP is connected to two flashes/SPI slave devices as shown in This Figure.
Traffic to SPI slaves can be controlled using the slave select register (SPISSR).