$FG$Bit operations are "atomic", no interrupt between the reading and writing the bit, important when multitasking. For multicore use "locked" forms.$FG$
$FG,5$These don't take a pointer, but the actual field.$FG$
$FG,2$Bsf$FG$: Bit Scan Fwd (Pos of first low one bit or -1)
$FG,2$Bsr$FG$: Bit Scan Rev (Pos of first high one bit or -1)