Digi ConnectCore 6UL Hardware Design Manuallines page 8

Schematics design checklist
☑
Item
BOOT
1. BOOT_MODE
[1:0]
2.
Recover/Debug
mode (USB)
3. Boot
configuration
lines
ConnectCore 6UL Hardware Design Guidelines
Description
These lines select the boot mode of the SOM:
BOOT_MODE1 BOOT_MODE0
0 0
0 1
1 0
1 1
By default, select the Boot from board settings option to boot from the
internal NAND memory. Use 10K resistors for pulling these line up or
down. When pulled-high, refer these lines to VDD_SNVS_IN. When this is
not possible (castellated pad configuration), use the 3V3_EXT power line.
Note BOOT_MODE0 is internally pulled-low. In the castellated version,
only BOOT_MODE1 is available externally.
To allow the system to boot from USB as a recovery/debug method, add
a jumper for shorting BOOT_MODE1 line to GND. This will force the
system to boot from fuses, and as long as they are not burned, the
system will fall into serial mode and boot from USB. This method is faster
than changing both BOOT_MODE[1:0] lines resistors to set up the Serial
Downloader, and can be helpful during the development phase when you
do not want to burn fuses.
The CPU can only boot from the USB_OTG1 bus. (USB_OTG2 is not
bootable.)
Make sure the BOOT_CFG1[7:0] lines are properly setup for booting from
the on-module NAND memory:
LCD_DATA0 (BOOT_CFG1[0]): pull-down
l
LCD_DATA1 (BOOT_CFG1[1]): pull-down
l
LCD_DATA2 (BOOT_CFG1[2]): pull-down
l
LCD_DATA3 (BOOT_CFG1[3]): pull-down
l
LCD_DATA4 (BOOT_CFG1[4]): pull-up
l
LCD_DATA5 (BOOT_CFG1[5]): pull-down
l
LCD_DATA6 (BOOT_CFG1[6]): pull-down
l
LCD_DATA7 (BOOT_CFG1[7]): pull-up
l
Use 10K resistors to pull these line up or down. When pulled-high, refer
these lines to 3V3_EXT.
Naming and signal conventions
Description
Boot from fuses
Serial downloader
Boot from board settings
Reserved
8