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91 lines
2.5 KiB
C
91 lines
2.5 KiB
C
/*
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* FreeLoader
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* Copyright (C) 1998-2003 Brian Palmer <brianp@sginet.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <freeldr.h>
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void sound(int freq);
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void delay(unsigned msec);
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VOID PcBeep(VOID)
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{
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sound(700);
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delay(200);
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sound(0);
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}
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void delay(unsigned msec)
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{
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REGS Regs;
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unsigned usec;
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unsigned msec_this;
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// Int 15h AH=86h
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// BIOS - WAIT (AT,PS)
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//
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// AH = 86h
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// CX:DX = interval in microseconds
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// Return:
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// CF clear if successful (wait interval elapsed)
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// CF set on error or AH=83h wait already in progress
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// AH = status (see #00496)
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// Note: The resolution of the wait period is 977 microseconds on
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// many systems because many BIOSes use the 1/1024 second fast
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// interrupt from the AT real-time clock chip which is available on INT 70;
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// because newer BIOSes may have much more precise timers available, it is
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// not possible to use this function accurately for very short delays unless
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// the precise behavior of the BIOS is known (or found through testing)
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while (msec)
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{
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msec_this = msec;
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if (msec_this > 4000)
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{
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msec_this = 4000;
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}
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usec = msec_this * 1000;
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Regs.b.ah = 0x86;
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Regs.w.cx = usec >> 16;
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Regs.w.dx = usec & 0xffff;
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Int386(0x15, &Regs, &Regs);
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msec -= msec_this;
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}
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}
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void sound(int freq)
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{
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int scale;
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if (freq == 0)
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{
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WRITE_PORT_UCHAR((PUCHAR)0x61, READ_PORT_UCHAR((PUCHAR)0x61) & ~3);
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return;
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}
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scale = 1193046 / freq;
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WRITE_PORT_UCHAR((PUCHAR)0x43, 0xb6);
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WRITE_PORT_UCHAR((PUCHAR)0x42, scale & 0xff);
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WRITE_PORT_UCHAR((PUCHAR)0x42, scale >> 8);
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WRITE_PORT_UCHAR((PUCHAR)0x61, READ_PORT_UCHAR((PUCHAR)0x61) | 3);
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}
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