Boot Order - Cherry PUMA SOM-RK3399-Q7 User Manual

Note: The fan is only necessary in high ambient temperatures. Under normal conditions, the RK3399-Q7
operates passively cooled.

3.5 Boot Order

The used boot order of the RK3399-Q7 module depends on the value of the BIOS_DISABLE# signal. On the
Haikou baseboard, this signal can be set using a slider switch, with the two positions labeled Normal Boot, and
BIOS Disable.
As shown in the table below, the BIOS Disable position disables both on-module storage devices:
If no bootloader is found on any storage device, the RK3399-Q7 module will go into USB loader mode where it
shows up as a USB device on the USB-OTG port.
The electrical state of the BIOS_DISABLE# signal for both slider positions is shown below:
RK3399-Q7 User Manual
© Cherry Embedded Solutions GmbH
Fig. 3.3: Fan connector
Normal Boot
1 SPI NOR flash
2 eMMC storage
3 SD card
4 USB loader
BIOS_DISABLE# signal
Slider Position
Normal Boot Floating (on-module pull-up to 1.8V)
BIOS Disable GND
BIOS Disable
SD card
USB loader
v1.6
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