For the configuration with Mode set to Dual and Slave Device set to Mixed, the core supports the commands listed in Table: Supported Commands in Dual SPI and Mixed Memory Mode, which are identical (in terms of command, address and data behavior) in Winbond, Micron and Spansion memory devices. See the memory data sheet for command details. The commands that are not supported in this mode include fast read, dual I/O fast read, and dual output fast read. These commands are not supported by the core in mixed mode because the dummy bytes or dummy cycles are different between the Winbond, Micron and Spansion devices.
Also, in mixed mode, the volatile configuration register of the Micron device is not supported as this command is not present in the Winbond device. See Following are the unsupported Commands for Dual/Quad SPI Mode across different memories of Winbond, Micron, Spansion, and Macronix. for a list of unsupported commands.