Boot Search Limit

Versal Adaptive SoC Technical Reference Manual (AM011)

Document ID

AM011

Release Date

2023-10-05

Revision

1.6 English

The BootROM has a search limit to locate the device image boot header for every boot mode. If a boot mode search limit is reached without a successful boot, the RCU goes into lockdown and the ERROR_OUT pin is set. The following table lists the boot image search limits for each mode.

Table 1. Boot Search Limit
Boot Mode¹	Search Limit²
OSPI (single, dual-stacked)	8 Gb (1 GB)
QSPI24 (dual-parallel)	256 Mb (32 GB)
QSPI24 (single, dual-stacked)	128 Mb (16 GB)
QSPI32 (dual-parallel)	8 Gb (1 GB)
QSPI32 (single, dual-stacked)	4 Gb (512 MB)
SD and eMMC	8191 FAT files (default)
eMMC (raw)	eMMC device size
When using OSPI or QSPI dual-stacked mode, the BootROM can only access the lower QSPI or OSPI addressable flash memory space for boot. After boot, the PLM can access the upper QSPI or OSPI for additional image storage. The search limit might exceed the size of the flash device. If the size of flash device is less than the search limit, when the RCU BootROM reaches the end of the flash address space, it will wrap around and continue the search at the flash address `0x0` if it has not met the search limit or read a valid image boot header. If the size of flash is equal to or greater than the search limit, the BootROM searches the image up to the search offset limit (example 8 Gb) regardless of which address the search began.

Note: See the Versal Adaptive SoC System Software Developers Guide (UG1304) for PLM fallback/MultiBoot management after a valid boot header is identified by the BootROM.