siewert@puff.UUCP (Dean Siewert) (04/26/86)
I'd like to thank anyone that might take the time to respond tothis.
I'm just starting in 8086 assembly langage and trying to get a program to
work that would copy the graphics screen from segment B800H to an unused
section of memory. the idea is that once several images are out in memory,
I could do very fast loads of these images into the video buffer.
Unfortunately, things are not working when the program terminates. The machine
hangs. Using SYMDEB, it looks that when the program hits the RET command, it
jumps off into never-never land.
Following is the code I've been working with:
TITLE Memory Mover
;----------------------Code Area Begins -----------------------------+
;
code segment public 'CODE'
assume cs:code,es:code,ds:code,ss:code
;
;----------------------Main Program Begins --------------------------+
;
; Program to pull a image from DEF SEG 3840 to the graphics display page
;
main proc far
;
push bp
push bx
push ax
mov ax, 0b800H
mov ds, ax
mov ax, 04000H
mov es, ax
mov bx, 2
label1:
; decrement counter
dec bx
; if ax less than zero then goto label2
cmp bx, 0
jl label2
; Move the value from &H4000,
; to &b800,
mov ax, es:[bx]
mov ds:[bx],ax
; goto label
jmp label1
label2:
; end program
nop
pop ax
nop
pop bx
nop
pop bp
nop
ret
main endp
code ends
end main
I have checked that the registers are left as they are when the
program is first entered and the stack is empty. Can someone give me
an idea of what I am doing wrong?
Also, I have learned that it doesn't work to define the data and extra
segment registers as pointing to some absolute addess by using:
DATA1 segment at B800H
in the data definition segemt. Is there some other way of doing this
than how I did it, (move the desired value into the ES and DS registers
manually?
Well, if anyone can give me some pointers, thanks.
Dean Siewert
siewert@puff.wisc.edu
University of Wisconsin-Madison