15 6a e2 7e    add. r23,r2,r13
    syntax  add. RT,RA,RB,OE=0,Rc=1
    opcode  0x7c000215
    mask    0xfc0007ff
    RT      0x17 (6, 7, 8, 9, 10)
    RA      0x2 (11, 12, 13, 14, 15)
    RB      0xd (16, 17, 18, 19, 20)