SPI flash devices from various vendors implement a standard instruction set for read operations. The system controller firmware executes the following command to identify the addressing mode (3-byte or 4-byte):
READ SERIAL FLASH DISCOVERY PARAMETER (5AH)
The system controller supports devices from Micron, Winbond, Macronix, and Spansion. However, any other device compatible with the JESD216 standard may also be used. Devices that are not JESD216-compliant may still be used if they support the FAST READ (0BH) command with 3-byte addressing. Such devices are limited to using only the first 128 Mb of the flash memory.