RM0082
BootROM
Doc ID 018672 Rev 1
827/844
Figure 112. Boot stages
38.2 Booting
Pins
Please look at section ‘
’ of “
After exiting the reset state, the ARM runs the Boot ROM code.
1) In case of flash booting, it will copy a second level boot code
from flash to the internal SRAM (Shadow memory) and jumps
into it. This mechanism is called ‘Code Shadowing’.
2) In case of Non - flash booting, it receives second level boot
code, execute it, and then receives third level boot code and
jumps into it.
3) Upgrade the flash through USB.
BootROM
This is the second - level boot code. It should be very small to fit
into the internal eSRAM(8KB) and knows the timing details of
the external SDRAM. It enables the SDRAM and
1) In case of flash booting, copies the third level boot code
and
jumps into it
.
2) In case of Non - flash booting, it jumps back to BootROM
This is the third - level boot code. It copies the primary OS into the
SDRAM and jumps into it.
Bootloader
This is the primary OS.
OS
X
-
Loader
