( cell contains both bytes. MSB is spit as-is, LSB is ORed
  with r )
( r -- )
: OP2r
    CREATE ,
    DOES>
    @ SPLITB SWAP   ( r lsb msb )
    A,              ( r lsb )
    SWAP <<3        ( lsb r<<3 )
    OR A,
;
0xed41 OP2r OUT(C)r,
0xed40 OP2r INr(C),