Maskrom mode(AKA DFU mode) is used to flash boot loader to boot media(used to be eMMC, SPI, Nand, SD card etc) over Rockusb Protocol.


When SoC boot up, The boot rom will read firmware from boot media(used to be eMMC, SPI, Nand, SD card etc). The boot rom automatically go to maskrom mode when it can not read anything from boot media or boot loader corrupted. In maskrom mode, The boot rom will talk to host PC with Rockusb Protocol over USB cable.

Use maskrom key

The maskrom key in hardware design just short the clock of boot media to ground. Which make boot rom can't read firmware from boot media. Three step to enter maskrom mode with maskrom key. If you don't have a maskrom key on your board. Just replace the maskrom key with "short the clock of boot media to ground".

  1. Long press MASKROM key(no release). This step short the clock of boot media to ground which will make boot rom can not read any thing from boot media. Please refer to here for the MASKROM key on Kylin board.
  2. Short press reboot key and release reboot key. This step trig SoC reboot.
  3. Count 3 second, release MASKROM key. This step is to make sure boot rom have go though all the boot media and failed. Then it automatically go to maskrom mode.

You can use "lsusb" command to check if you are really in maskrom mode. You will find a USB device with VID 0x2207 in your computer.

$ lsusb
Bus 002 Device 062: ID 2207:301a