output function problem

[suthers]

I use the following code for output:

Code: Select all

PutStr_32:
	xor ax, ax
	mov ds, ax
	mov eax, screen_pos 	
	.nextchar	
 	lodsb		
 	or al,al	
 	jz .return	
	mov byte [ds:eax], al
	inc eax
	mov byte [ds:eax], 1Bh
 	jmp .nextchar	
	.return
	mov [screen_pos], eax
	ret	   
        ;data
        screen_pos dd 0

It loads a character form the si registry into al and the prints it to the screen, it assembles without any error or warnings, but when i run it on vmware, it just restarts.
Can anybody tell me what is the cause of this error? (I am in protected mode by the way)
Thanks in advance,

Jules

[mgarcia]

You are setting ds to 0, the null segment selector.