Surviving 1 second without battery power

[peu]

Im trying to understand how this LED flashlight driver works, so I can implement the same technique on my own design.

The driver is powered by a single 3.6v Li-ion battery and by powering it off-on in less than a second it changes modes: Hi 100% > Mid 35% > Lo 20% > Strobe > SOS

Here is the link to it:
http://www.dealextreme.com/details.dx/sku.6190
AMC7135 Datasheet

And here is the Schematic I drawn from inspecting the PCB:


It obviously detects when power goes off, but I don't have the slightest clue on how its done, if I have to think of some PIC function that does that it would be BOD, but to be honest, Im lost.

The capacitor in the schematic may work as a battery backup, but its rather small, so upon battery power lost the PIC must be configured to keep consumption to a minimum.

Any help will be appreciated!