Kernel Recovery Mode - ZyXEL Communications U-336R/RE User Manual

10. When the installation is complete, the modem restarts

Kernel Recovery Mode

Your modem is equipped with ZyXEL's exclusive Kernel
Recovery Mode. This unique feature enables quick recovery from
failed flash uploads. With other modems, a failed flash upload
usually results in the user having to return the modem to the factory
for repair.
In the unlikely event that your modem fails to respond to AT
commands after upgrading the flash EPROM:
1. Turn off the modem.
2. Press and hold down the A/O button while turning on the
3. A Kernel Program responsible for the update process takes
Repeat steps 1 through 6 from the directions above to upload a file
that contains valid firmware for your modem.
132 Upgrading Your Modem
automatically.
modem, then release the button after 5 seconds.
control of the modem. It accepts a limited set of AT commands,
including the ATUPX command.