Boot options (AxelLite)

Info Box Applies to Axel Lite

System boot

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

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

Selection of primary boot device is determined by the BOOT_MODE_SEL signal as follows:

• BOOT_MODE_SEL = 0
  • primary boot device is SD1
• boot ROM will try to boot a valid image from the SD card first, and then from the SPI NOR. In case no valid image is found, 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
  • in case no valid image is found in NOR flash, boot ROM shall enable USB serial download mode automatically

NAND / SD option

Selection of primary boot device is determined by the BOOT_MODE_SEL signal as follows:

• BOOT_MODE_SEL = 0
  • primary boot device is SD1
  • 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
  • in case no valid image is found in NAND flash, boot ROM shall enable USB serial download mode automatically