When the Flash device is not present
or discoverable from the JEDEC response, the bootloader looks for an image to be loaded
via SPI or UART interface, if the first ping/command is initiated through SPI interface
then RBL switch to SPI mode of image download. This image can be loaded in from a host
PC or external processor. For more details on booting over SPI, see the
AWRL6432,
IWRL6432, AWRL1432, IWRL1432 Technical Reference Manual.