An emergency-recovery-sort-of, download mode.
Just flash matching version rom, depending on what you were trying to do.
If it was android or null_rom, reflash android.
if it was android and you wanted to upgrade it to Tizen, flash the very first version of tizen (NE9), not the newer NF1.
NE9 allow to upgrade Android to Tizen, NF1 just allow to update Tizen to newer Tizen, and bricks Gear if trying to upgrade from Android.