When a character grabs the edge, they
first go into the ledge grabbing
animation, which is uninterruptible
and totally inincible. For everyone
but Link, this animation is 7 frames
long; for Link, it's 3 frames.

Immediately following this is the
ledge hang animation. It grants 30
frames of invincibility, which don't
go away no matter if you drop off or
whatnot. For whatever reason, the
first frame of this hanging animation
can only be interrupted by certain
actions.

YES

Jump
Attack
Roll

NO
Stand
Drop

You can hang on the edge for a max
of 640 frames, or 10 2/3 seconds.

You cannot grab an edge if you were
grabbing it within the last 30
frames. I.E. if you drop off and
consider that frame 1, you can't grab
that same edge again until frame 30.