aka j wrote:
-------------------------------
>If so, P1 and P2 will be used to present an address when accessing that memory block
Sorry, Jay, it must be P0 and P2.

Jason,

>How does Port 2 differ in construction from lets say, Port 1 or 3?
Nothing in your case. But don't forget that the undisturbed contents of the port 2 SFR reappear in the next cycle.

It is possible to use the upper two bits from Port 2 as general outputs. It is easy enough. There is a little program trick here. Let's reserve an image of your external address before putting it into DPTR and look at some cases.

1) Suppose you want to set p2.7 bit of port 2. You have to write next code
ORL HI_IMAGE,#1000000B
MOV P2,HI_IMAGE

2) Suppose you want to clear p2.7 bit of port 2. You have to write next code
ANL HI_IMAGE,#01111111B
MOV P2,HI_IMAGE

3) Suppose you want to get any byte from external memory. You concatenated the 7 or/and 6 bits with desired high byte address before, so you have to write next code
MOV DPH,HI_IMAGE
MOV DPL,LO_IMAGE
MOVX A,@DPTR

The similar trick you can use if you have external code ROM of 16 KB. Suppose you want to set p2.7 bit of port 2. You have to write next code
MOV DPTR,#NXTADDR
XCH A,DPH
SETB ACC.7 ;or bit 6 or both
XCH A,DPH
JMP @DPTR
NXTADR: ...........

Hope this examples are enough to understand the main idea.

George