Using the System
The i.MX6UL/ULL SoM has the two boot pins on the SoC (BOOT_MODE0 and BOOT_MODE1) unconnected by default, which means the boot mode is set to "00". The BootROM will use the manufacture-mode to look for a bootable image on the SD-card. If none is found, it will fall back to serial loader mode, where it expects an image to be loaded via USB-OTG1 (which is on the micro USB connector on the demo board).
To select other boot devices such as the SPI NOR flash or the eMMC, you need to program the OTP fuses accordingly.
The default setup for production devices from Kontron is that the fuses are set to boot from the SD card (SD1) as primary boot device. The SPI NOR is set as fallback boot device if no SD card is available.
The following OTP register values will be used:
|BOOT_CFG||0x450||0x49002040||Boot from SD (SD1, 4bit buswidth, 3.3V), enable alternative boot from NOR (SPI2, 3-byte addressing, CS0)|
|BT_FUSE_SEL||0x460||1||Boot from fuses|
If you order SoMs from Kontron and you need a different setup, please supply the necessary information with your order.