I’ve got to do it this weekend, and don’t get to use REV, so this is what I came up with (untested).
There’s another thread about REV somewhere.. it was decompiled to find out instruction time,
and I don’t know right now If I’m beating it.

Code:
sixteenbit var word
revsixteen var word

leasteight var sixteenbit.byte0
mosteight var sixteenbit.byte1
leastrev var revsixteen.byte0
mostrev var revsixteen.byte1

count var byte


reversesixteen:

for count = 0 to 7

leastrev.bit7 = mosteight.bit0
mosteight << 1
leastrev >> 1

mostrev.bit7 = leasteight.bit0
leasteight << 1
mostrev >> 1

next count

return