Regarding absolute address

 RE: Regarding absolute address

"i want to place my fn()1 in xdata"

What exactly do you mean by "fn()1"??

Note that the 8051 architecture can only ever execute from CODE space - it cannot execute anything stored in XDATA!

 RE: Regarding absolute address

In olden days, most 8051s MCUs kept their xdata and code
space off-chip. You could then OR the PSEN\ and RD\ signals
together, causing the xdata and code spaces to overlap.

This totally defeats the advantages of selecting a Harvard
architecture in the first place, and I would guess nobody
uses those pre-historic processors anymore, anyway.

 RE: Regarding absolute address

would guess nobody
uses those pre-historic processors anymore, anyway.

Wrong on two counts. First, there's nothing pre-historic about 8051s with external memory. A CPU like the DS80C390 is by no means pre-historic. It's certainly unusual for an 8051, but it's quite current. They even still do mask revisions.

Second, your guess is wrong. Even processors very much like the original '51s are still used, even today. You try to find a rad-hard 8051 with internal memory, you'll know why.

 RE: Regarding absolute address

Hans-Bernhard: an old saying goes: "it takes an exception to confirm a rule", so your post "wrong!" actiually confirms that Gary is right :)

Erik