The AXI Quad SPI core is tested in hardware with SPI slave devices such as Micron, Winbond, Macronix, and Spansion Flash memories in standard SPI mode. Standard, dual and quad modes are tested with Winbond, Micron, Spansion, and Macronix SPI flash memories. Read the data sheet of the targeted SPI slave flash memory or EEPROMs for the maximum speed of operation. Ensure that the correct values are used when deciding on the AXI clock and selecting the Frequency Ratio parameter. The AXI clock and the Frequency Ratio parameter determine the clock frequency at the SCK pin of the core. While using different external SPI slave devices, the Frequency Ratio parameter should be set carefully, and the maximum clock frequencies supported by all the external SPI slave devices should be taken into account.