By: Masud-ul-Hasan
21
External Data Memory
•64K byte address space.
•The only access to this memory is with the MOVX instruction, using either 16-bit data pointer DPTR, R0, or R1 as the address register.
8051
PORT 2
ALE
PORT 0
WR
RD
RAM(S) or I/O
CE
        DATA OUTPUTS
   ADDRESS INPUTS
R/W
OE
   ADDRESS LATCH
DECODER