reactos/boot/freeldr/freeldr/arch/i386/i386rtl.c

   1 /*
   2  *  FreeLoader
   3  *  Copyright (C) 1998-2003  Brian Palmer  <brianp@sginet.com>
   4  *
   5  *  This program is free software; you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation; either version 2 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program; if not, write to the Free Software
  17  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18  */
  19
  20 #include <freeldr.h>
  21
  22 void PcBeep(void)
  23 {
  24         sound(700);
  25         delay(200);
  26         sound(0);
  27 }
  28
  29 void delay(unsigned msec)
  30 {
  31         REGS            Regs;
  32         unsigned        usec;
  33         unsigned        msec_this;
  34
  35         // Int 15h AH=86h
  36         // BIOS - WAIT (AT,PS)
  37         //
  38         // AH = 86h
  39         // CX:DX = interval in microseconds
  40         // Return:
  41         // CF clear if successful (wait interval elapsed)
  42         // CF set on error or AH=83h wait already in progress
  43         // AH = status (see #00496)
  44
  45         // Note: The resolution of the wait period is 977 microseconds on
  46         // many systems because many BIOSes use the 1/1024 second fast
  47         // interrupt from the AT real-time clock chip which is available on INT 70;
  48         // because newer BIOSes may have much more precise timers available, it is
  49         // not possible to use this function accurately for very short delays unless
  50         // the precise behavior of the BIOS is known (or found through testing)
  51
  52         while (msec)
  53         {
  54                 msec_this = msec;
  55
  56                 if (msec_this > 4000)
  57                 {
  58                         msec_this = 4000;
  59                 }
  60
  61                 usec = msec_this * 1000;
  62
  63                 Regs.b.ah = 0x86;
  64                 Regs.w.cx = usec >> 16;
  65                 Regs.w.dx = usec & 0xffff;
  66                 Int386(0x15, &Regs, &Regs);
  67
  68                 msec -= msec_this;
  69         }
  70 }
  71
  72 void sound(int freq)
  73 {
  74         int scale;
  75
  76         if (freq == 0)
  77         {
  78                 WRITE_PORT_UCHAR((PUCHAR)0x61, READ_PORT_UCHAR((PUCHAR)0x61) & ~3);
  79                 return;
  80         }
  81
  82         scale = 1193046 / freq;
  83         WRITE_PORT_UCHAR((PUCHAR)0x43, 0xb6);
  84         WRITE_PORT_UCHAR((PUCHAR)0x42, scale & 0xff);
  85         WRITE_PORT_UCHAR((PUCHAR)0x42, scale >> 8);
  86         WRITE_PORT_UCHAR((PUCHAR)0x61, READ_PORT_UCHAR((PUCHAR)0x61) | 3);
  87 }