ZyXEL Communications U-336SA - Manual (Page 155)

Upgrading Your Modem 141
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 the D/V button while turning on the modem, then release the
button after 5 seconds.
A Kernel Program responsible for the update process takes control
of the modem. It accepts a limited set of AT commands, including
the ATUPX command.
3. Repeat steps 1 through 9 from the previous directions above to
upload a file that contains the valid firmware for your modem.