From: king621@nospicedham.comcast.net   
      
   On 12/26/19 8:29 AM, s_dubrovich@nospicedham.yahoo.com wrote:   
   > On Thursday, December 26, 2019 at 3:53:21 AM UTC-6, 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   
   >>   
   >> ; prints 4 hex digits from stack   
   >>   
   >> vuhex:	pop ax		;4 hex digits   
   >> 	mov di,3832	;l.r. corner   
   >> 	mov cx,4	;;# of hex digits   
   >> vh01:	rol ax,4	;hi digit on right   
   >> 	push ax		;push rol'd ax   
   >> 	and al,0x0f	;;masks right digit   
   >> 	add al,'0'	;0 thru 9   
   >> 	cmp al,'9'   
   >> 	jbe vh02   
   >> 	add al,0x7		;A thru F   
   >> vh02:	mov byte[es:di],al   
   >>    	inc di   
   >> 	mov byte[es:di],0x0f	;blk/wht   
   >> 	inc di   
   >> 	pop ax		;pop rol'd ax   
   >> 	loop vh01   
   >>   
   >> 	jmp $   
   >   
   > SECTION  .data   
   >   
   > fat5 dw 0xaa99,0xbb88,0xcc77,0xdd66,0xee55,0xff44   
   >   
   > ;; prints 77BB, should be DD66   
   >   
   > ;; fat5: db 99h, 0AAh, 88h, [0BBh, 77h], 0CCh, {66h, 0DDh}, 55h, 0EEh, 44h,   
   0FFh   
   >   
   > ;; SI = 3 points to [nnnnh], as db 99h is at index (offset) 0   
   >   
   > '[]' brackets the actual result   
   > '{}' brackets the desired result   
   >   
   > SECTION  .text   
   >   
   > ;	mov	si, 3   
   > ;	mov	ax, word[fs:si]   
   >   
   > ;; SI needs to be a word index (offset), 3*2, to point to {nnnnh}   
   > ;; SI = 0000h points to byte 99h, plus 6 then points to the low order byte   
   66h,   
   > ;; the high ordered byte is DDh.   
   > ;; The correction is:   
   > ;;   
   > ;;	mov	si, 3*2   
   >   
   > Steve   
   >   
      
   Thanks for your explanation, I realized my mistaken thinking as soon as   
   I saw it.   
      
   --- SoupGate-Win32 v1.05   
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