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   comp.lang.asm.x86      Ahh, the lost art of x86 assembly      4,675 messages   

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   Message 3,999 of 4,675   
   wolfgang kern to All   
   Re: Isn't this anomalous behavior? What    
   26 Dec 19 23:22:41   
   
   From: nowhere@nospicedham.never.at   
      
   On 26.12.2019 11:21, bilsch01 wrote:   
   > The code below writes 5 words to memory at 0x37000. I verified the words   
   > are there using code not shown (for simplicity), but it's easy to see   
   > that the words should be there. After that the 2 lines:   
   >   
   >   
   > mov si,3   
   > mov ax,word[fs:si]   
   >   
   > should put dd66 in ax register but instead it puts a byte from each of 2   
   > other words in ax, specifically 77bb. The routine at the end prints the   
   > result 77BB when it should print DD66.   
   >   
   > I have a situation where I really need something like this to work. How   
   > can I do it?   TIA.   Bill S.   
   >   
   > bits 16   
   > org 0x0000   
   >   
   > SECTION  .data   
   >   
   > fat5 dw 0xaa99,0xbb88,0xcc77,0xdd66,0xee55,0xff44   
   >   
   > SECTION  .text   
   >   
   > push 0   
   > pop ss   
   > mov sp,0x7aff   
   > push 0x1000   
   > pop ds   
   > push 0xb800   
   > pop es   
   >   
   > ; write 5 words to mem at 0x37000   
   >   
   > push 0x3700   
   > pop fs   
   > mov di,0   
   > mov si,fat5   
   > mov cx,5   
   >   
   > fatlu:   
   > mov ax,word[ds:si]   
   > mov word[fs:di],ax   
   > add si,2   
   > add di,2   
   > loop fatlu   
   >   
   > ; here's the test   
   >   
   > mov si,3   
   > mov ax,word[fs:si]   
   >   
   > push ax   
   > jmp vuhex    ;prints 77BB should be DD66   
      
   77BB is correct because of the above mov si,3   
   will need mov si,6 to see DD66 !   
   __   
   wolfgang   
   > ; prints 4 hex digits in l.r. corner   
   >   
   > vuhex:   
   > pop ax   
   > mov di,3832   
   > mov cx,4   
   >   
   > vh01:   
   > rol ax,4   
   > push ax   
   > and al,0x0f   
   > add al,'0'   
   > cmp al,'9'   
   > jbe vh02   
   > add al,0x7   
   >   
   > vh02:   
   > mov byte[es:di],al   
   > inc di   
   > mov byte[es:di],0x0f   
   > inc di   
   > pop ax   
   > loop vh01   
   >   
   > jmp $   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)   

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