I've recently made a MCU-51 experimental board, including a 8052, 8282(Address latch) and a 62256.

P0 and P2 are assigned to external data/program RAM only. I have given three 10Kohms pull-up resistors to P0(DATA/A0-A7),P2(A15-A8) and one on the other side of 8282 for latched address bus A0-A7.

/CS of 62256 has connected to GND
/OE has connected to /RD of 8502
/WE has connected to /WR of 8502

(/RD and /WR are using internal pull-up resistors on Port3)

MOV DPTR,#0000H
MOV A,#0AAH
MOVX @DPTR,A
MOV A,#00H
MOVX A,@DPTR
MOV P1,A

so that I expect 0xAA through P1.0 to P1.7

The result returned on P1 is always 0xFF

By the way, what data is filled in 62256 as soon as power applied? 0xFF or random bytes?

Is the problem on the BUS system? Or caused by those errors during /CE /OE /WR timing and operation issues?

Thank you so much!