8051 Microcontroller Descending Order

I suspect that your "JNC" version didn't really work either. The numbers may have ended up sorted only because they were partially sorted to begin with.
Perhaps you should post the full sort program - not just the first page.
I would also be good if you could post it right-side up.

 

For everyones information: DPL is the low-order byte of DPTR.

You are overwriting R0 with it - which may be you're intention. I can't tell.

I think the problem is that when you loop from DJNZ R1,L3, R0 is not reset.

 

This isn't a bubble sort. DPTR should only be incremented once per loop. After a compare (subtract and restore A), if the elements are not in order, then decrement DPTR, store the smaller (or larger if descending) number, increment DPTR and store the larger (or smaller if descending). If the elements are in order, then skip to the end of the next inner loop. The idea here is to move the largest (or smallest if descending) element to the end of the array on each loop. The "size" of the array can be decremented on each loop since the largest (or smallest) values are already moved to the end.

 

That's why I put the note about DPL in my last post.
He increments DPTR twice and decrements the low order byte once. As long as his list is less than 160 bytes long, he's okay.

 

Why not use this to decrement DPTR, and also avoid overwriting R0?

Code (Text):

        XCH     A,DPL
        JNZ     D1
        DEC     DPH
D1:     DEC     A
        XCH     A,DPL