From: "Mauro Da Ros" <daros AT elettra80 DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: **HELP** direct memory access...
Date: Fri, 18 Dec 1998 10:03:38 +0100
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Ciao
I have a numeric control with a static RAM beginning at 0xd0000.
So I wrote this functions :


#define RAMTAMPONE 0xd0000

external struct PAR par;  // struct to store in SRAM


void Dmempoke ( int ofs , unsigned char c) {
    _farsetsel (_dos_ds);
    _farnspokeb ( RAMTAMPONE + (long) ofs, c);
}

unsigned char Dmempeek ( int ofs ) {
    _farsetsel (_dos_ds);
    return _farnspeekb ( RAMTAMPONE + (long) ofs);
}


void RWRam(bool write) {        // write-read the parameter struct in SRAM
  unsigned char *c;
  c = (unsigned char*)&par;
  if (write) {
    for (int i=0;i<sizeof(PAR);++i) {
       Dmempoke (i,c[i]);
    }
  }
  else {
    for (int i=0;i<sizeof(PAR);++i) {
        c[i] = Dmempeek (i);
    }
  }
}



PAR is the struct with my parameters to store in static ram.
The very strange thing is that if I make a simple test program
with

par.t1 = 10;
RWRam (true); // (write)
par.t1 = 0;
RWRam (false); // (read)

it works. If i enclose in my allegro application (780 K)  it, it
DOESN'T WORK :((((
I think there are problems on that  _dos_ds, but I don't know
WHAT to use !!!

Please help me... and please cc in email

Ciao

    Mauro
    daros AT elettra80 DOT com