Boot options (AxelLite)
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System boot[edit | edit source]
The boot process begins at Power On Reset (POR) where the hardware reset logic forces the ARM core to begin execution starting from the on-chip boot ROM. The boot ROM:
- determines whether the boot is secure or non-secure
- performs some initialization of the system and clean-ups
- reads the mode pins to determine the primary boot device
- once it is satisfied, it executes the boot code
Boot options[edit | edit source]
Two options are available related to system boot. They are identified by the Boot field of the ordering code as follows:
- 0: SPI NOR / SD option (SOM code: DXLxxxx0xxR)
- 1: NAND / SD option (SOM code: DXLxxxx1xxR)
For both options the selection of primary boot device is determined by the BOOT_MODE_SEL signal as described in the following sections. BOOT_MODE_SEL is latched when processor reset is released.
In any case, boot process is managed by on-chip boot ROM code that is described in detail in processor's Reference Manual.
SPI NOR / SD option[edit | edit source]
Selection of primary boot device is determined by the BOOT_MODE_SEL signal as follows:
- BOOT_MODE_SEL = 0
- primary boot device is SD1 (see section TBD for more details)
- in case no valid image is found in SD card, boot ROM shall enable USB serial download mode automatically
- BOOT_MODE_SEL = 1 or floating
- primary boot device is SPI NOR flash connected to eCSPI1 (see section TBD for more details)
- in case no valid image is found in NOR flash, boot ROM shall enable USB serial download mode automatically
NAND / SD option[edit | edit source]
Selection of primary boot device is determined by the BOOT_MODE_SEL signal as follows:
- BOOT_MODE_SEL = 0
- primary boot device is SD1 (see section TBD for more details)
- in case no valid image is found in SD card, boot ROM shall enable USB serial download mode automatically
- BOOT_MODE_SEL = 1 or floating
- primary boot device is NAND flash (see section TBD for more details)
- in case no valid image is found in NAND flash, boot ROM shall enable USB serial download mode automatically
