All SPI boot modes use the chip select 0 signal. The appropriate pin (SPI0_SCS[0] or SPI1_SCS[0]) must be connected to the external SPI device.
The SPI EEPROM device must use 16-bit addressing, and its read command must equal 0x03. The bootloader will look for an AIS image at offset 0x00000000.
The SPI flash device must use 24-bit addressing, and its read command must equal 0x03. The bootloader will look for an AIS image at offset 0x00000000.
In the SPI-boot modes, the received data is sampled at the rising edge of the clock and the data to be transmitted on the falling edge of the clock as shown in Figure 27:
Figure 27. SPI Mode for Communication
Figure 28. SPI Signal Diagram for SPI EEPROM Boot (with sequential read enabled)