The EM3566 supports Normal mode and Upgrade mode. Normal mode is the normal startup process. Maskrom and Loader mode are used for USB download firmware, and Recovery mode for SD Card startup/upgrade.

Mode	Flashing tools	Describe
Maskrom	Support	1. If the eMMC is empty, the board automatically enters the MASKROM Upgrade mode when it is powered on 2. when the bootloader verification fails (the IDB block cannot be read, or the bootloader is damaged), the BootRom code will enter this mode.
Loader	Support	In the Loader mode, can download and upgrade firmware. You can flash a partition image piece separately through the tool to facilitate debugging.
Recovery	Not Support	The system guides the recovery to start, mainly for upgrade operations.
Normal Boot(eMMC /SDMMC)	Not Support	The system guides the rootfs to start, loads rootfs, and most of the development is debugged in this mode.

1. Maskrom Mode

If there is no bootable firmware found on board, the SoC will run Rockusb driver automatically, we call it Bootrom mode or Maskrom mode. User can get into this mode via EraseFlash (software) or short the eMMC clock to GND (hardware).

1.1 Software to Maskrom

Step 1, unzip AndroidTool.zip or RKDevTool_Release_v2.93.rar on Windows.

Step 2, open RKDevTool_Release_v2.93\RKDevTool.exe

Step 3, connect PC and development board with Micro USB cable, keep pressing the Recovery key and power up the board until the windows PC shows Found One LOADER Device, release the key.

Step 4, click Advanced Function -> EraseAll to erase flash. After erase flash will enter Maskrom mode.

1.2 Hardware to Maskrom

Step 1, Connect PC and development board with Micro USB cable.

Step 2, Short circuit the signals eMMC_CLKOUT and GND to enter Maskrom mode.

Warning

Please be careful to avoid touching the extraneous components to cause short circuit and damage the development board.

Step 3, Power on. The device will enter Maskrom mode.