Dissidia 012 Duodecim Final Fantasy - ULUS10566

[LunaMoo]

Refresh rate doesn't matter, it's required only by cheats that race against game, which usually means one or the other - cheats that patch code that runs on boot, or cheats that patch temporary variables which change every frame - really awful thing to mess with, unfortunately some people can't do any better.

As for what the cheat does it basically changes the branch here:
   
To compare zero with zero ~ which is always true and skips all the code under.
If you look closely there are more branches inside, a bunch of them leads to 0x08AEEB1C which is writing value of f14 register to memory - where assist is stored. That register in this place will be 5k(one bar) or 10k(two bars ~ which is passed from f15 if correct branch is taken earlier).

I found it by cpu vs cpu battle(that is "tactics" mode to just give commands) and checking what writes where assist is stored, and nopping all other code that wrote values to assist without filling the bar to full. I was more looking in the code than what actually happens, but pretty sure it triggered when attack was defended with very low hp.
If it patches the memory correctly, but doesn't work, there must be more situations that reward with full bar, as said I'm not confident of triggering this myself, if you can make a savestate right before triggering what you call full charge ~ by CPU so no player input is required, that would make things easier.