1.) Turn on the power switch of DM820 at the back
2.) Press Power-Button at the front until on display appears "entering setup"
3.) Now you can release Power-Button and DM820 is in Rescue Mode
4.) You have to enter via browser -> "http://dm820" (without "" ) or IP-Adress of DM820 which is shown on display
5.) You will see Rescue Mode of DM820. Click "Firmware upload"
6.) Now click "Select File" and then choose image for the DM820 and after that click "Select"
7.) Next you have to click "Go!" and DM820 starts with flashing
8.) After flashing click on "Click here to reboot" and wait until DM820 is rebooting