From:	"Greg Holdridge" <greg AT holdridge7 DOT freeserve DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	PS: A mysterious event
Date:	Sun, 13 Aug 2000 17:36:27 +0100
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To:	djgpp AT delorie DOT com
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Actually, sometimes a SIGSEGV occurs instead of power off on monitor- this
highlights that the problem occurs during a lodsw loop:

--- code cited ---

{From start of SetMode.asm}
[SECTION .data]

; 320x240 data

CRTParms320x240:
 dw      00d06h  ;vertical total
        dw      03e07h  ;overflow (bit 8 of vertical counts)
        dw      04109h  ;cell height (2 to double-scan)
        dw      0ea10h  ;v sync start
        dw      0ac11h  ;v sync end and protect cr0-cr7
        dw      0df12h  ;vertical displayed
        dw      00014h  ;turn off dword mode
        dw      0e715h  ;v blank start
        dw      00616h  ;v blank end
        dw      0e317h  ;turn on byte mode
CRT_PARM_LENGTH320x240 equ     (($-CRTParms320x240)/2)

[SECTION .text]

{From later in SetMode.asm}

mov     esi,CRTParms320x240 ;point to CRT parameter table
mov     cx,CRT_PARM_LENGTH320x240 ;# of table entries
.SetCRTParmsLoop:
   lodsw           ;get the next CRT Index/Data pair
   out     dx,ax   ;set the next CRT Index/Data pair
   loop    .SetCRTParmsLoop

--- end code citing ---

As you can see, word outs are used.  Is there a problem with this sort of
code in NASM? This is definitely causing a segment violation.

Thanks again,

Greg

- Raw text -