Fallback boot allows the Versal ACAP to automatically boot a different PDI than the initial PDI on the same primary boot device, if the first PDI fails to boot. If an error occurs during the PDI boot sequence, the PLM increments the MultiBoot register by 1 and resets (SRST) the device so that the BootROM can find the next good image.
An error during boot PDI load can occur due to various reasons. Some examples for PLM errors include:
- PDI header fields are not valid
- Copy from boot device has failed.
- Unavailability of power while loading corresponding power domain CDOs (LPD, FPD, NPD, PL, etc.).
- Checksum or decryption or authentication failure while loading partitions, if enabled.
- Command failures (such as DDR memory calibration
mask_pollcommand time out) during CDO processing.
MultiBoot allows the Versal ACAP to boot from a different boot PDI other than the initial PDI. You can specify the boot PDI to be used for booting in this case. The PLM provides a command for user applications to update the multiboot value during run-time. For more information, see the XilLoader/IPI CDO Commands.
To use fallback boot or MultiBoot, store multiple PDIs in the same primary boot device within the search limit for the device. For information, see the Primary Boot Devices table in Boot Device Modes.