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From:	"Marp" <marp AT 0 DOT 0 DOT 0 DOT 0>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: problem with __dpmi_int()
Date:	Mon, 4 Sep 2000 11:10:58 -0400
Organization:	MindSpring Enterprises
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"Ricardo Cropalato de Melo" <cropalat AT svn DOT com DOT br> wrote in message
news:sr79j8h7a6e143 AT corp DOT supernews DOT com...
> I 'm trying to read a floppy sector / sector, and i was doing it like this
> code:
>

<snip>

>  char setor[512] = "Teste";

<snip>

>     regs.x.es = _my_cs();
>     regs.x.bx = (unsigned) setor;

This is no good. "sector" most likely resides in memory above the
addressable range for real mode, and cs is a selector, not a real mode
segment address. You must use memory that has been allocated in conventional
memory. DJGPP allocates some of this memory and use it as a transfer buffer.
You can just use that instead of allocating the memory yourself.

So it should look something like this:

dosmemput(sector, sizeof(sector), __tb);
regs.x.es = __tb >> 4;
regs.x.bx = __tb & 0xf;
__dpmi_int(0x13, &regs);
dosmemget(__tb, sizeof(sector), sector);

You have to do something like this for any real mode ISR that requires a
real mode far pointer. Also, read chapter 18 of the djgpp faq for details on
why you need to do this. Hope this helps.

Marp

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