There are devices that implement custom 4-bit wide SPI-like interfaces for flash memory access. Other Quad-SPI devices offer an option to switch operation to a custom 4-bit interface, through a non-volatile configuration bit. These interfaces operate differently from the devices supported by the dual controller. These flash memory devices operate in 4-bit mode during the instruction phase, as well as the address and data phases. This requires the Quad-SPI flash controller to power up in 4-bit mode and remain in that mode permanently (or until otherwise configured, if the option is available). The dual controller does not offer support for these custom interfaces.