i386rtl.c

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/*
 *  FreeLoader
 *  Copyright (C) 1998-2003  Brian Palmer  <brianp@sginet.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <freeldr.h>

void sound(int freq);
void delay(unsigned msec);

void PcBeep(void)
{
    sound(700);
    delay(200);
    sound(0);
}

void delay(unsigned msec)
{
    REGS        Regs;
    unsigned    usec;
    unsigned    msec_this;

    // Int 15h AH=86h
    // BIOS - WAIT (AT,PS)
    //
    // AH = 86h
    // CX:DX = interval in microseconds
    // Return:
    // CF clear if successful (wait interval elapsed)
    // CF set on error or AH=83h wait already in progress
    // AH = status (see #00496)

    // Note: The resolution of the wait period is 977 microseconds on
    // many systems because many BIOSes use the 1/1024 second fast
    // interrupt from the AT real-time clock chip which is available on INT 70;
    // because newer BIOSes may have much more precise timers available, it is
    // not possible to use this function accurately for very short delays unless
    // the precise behavior of the BIOS is known (or found through testing)

    while (msec)
    {
        msec_this = msec;

        if (msec_this > 4000)
        {
            msec_this = 4000;
        }

        usec = msec_this * 1000;

        Regs.b.ah = 0x86;
        Regs.w.cx = usec >> 16;
        Regs.w.dx = usec & 0xffff;
        Int386(0x15, &Regs, &Regs);

        msec -= msec_this;
    }
}

void sound(int freq)
{
    int scale;

    if (freq == 0)
    {
        WRITE_PORT_UCHAR((PUCHAR)0x61, READ_PORT_UCHAR((PUCHAR)0x61) & ~3);
        return;
    }

    scale = 1193046 / freq;
    WRITE_PORT_UCHAR((PUCHAR)0x43, 0xb6);
    WRITE_PORT_UCHAR((PUCHAR)0x42, scale & 0xff);
    WRITE_PORT_UCHAR((PUCHAR)0x42, scale >> 8);
    WRITE_PORT_UCHAR((PUCHAR)0x61, READ_PORT_UCHAR((PUCHAR)0x61) | 3);
}