The BootROM runs at an OSPI device clock frequency between 11 MHz and 24.5
MHz dependent on the reference clock input frequency. During BootROM execution, the
OSPI boot mode supports an 8-bit data bus width and a single data rate (SDR). The
BootROM code first initiates the boot sequence with the default 4-byte address octal
output fast read command code 7Ch and searches for
a valid boot header. If a valid boot header is not found, the BootROM attempts to
load the image using the 4-byte alternate addressing read command code 13h. If a valid boot header is still not detected, the
basic read command 03h is loaded. If the boot
attempt is unsuccessful after the third command, the BootROM increments the
MultiBoot register
(
PMC_MULTI_BOOT
)
read address offset by 32 KB and tries the OSPI command sequence again to locate a
valid boot header. If the OSPI boot mode search limit is reached without a
successful boot, the RCU goes into lockdown and the ERROR_OUT pin is set.
The image search limit for each boot mode is listed in Boot Search Limit.