A little bit less code:
<pre>
decode:
mov a, P0
anl a, #7
add a, #dec3-dec1
movc a, @a+pc
dec1:
mov r2, #0
jb P0.3, dec2
xch a, r2
dec2: mov P1, r2
mov P2, a
ret
dec3:
db 1, 2, 4, 8, 16, 32, 64, 128


Peter