Well, the 374' works just fine.
Again, the problem is that the following
does not work:

MOV A,#0xFF
MOV DPTR,#0x5555
MOVX @DPTR,A

What I'm expecting to happen:

OP 0 1 2
-----------------------------
AD0-7: 0x55 0x55 0xFF
ALE: L H L
AD8-15: 0x55 0x55 0x55
/WR: H H L

What IS happening:

OP 0 1 2
---------------------------------
AD0-7: 0xFF 0xFF 0xFF
ALE: HLHLHLHLHLHLHLHLHLHLHLHLHLHL
AD8-15: 0xFF 0xFF 0xFF
/WR H H H