/*
Copyright (C) Magna Carta Software, Inc. 1987-1991.  All Rights Reserved.
SOUND -- Program the 8253 to produce sound independently of the CPU
Note: This procedure uses the BIOS time-of-day count to control the
duration and so is only accurate to approximately 55 milliseconds.
*/

#define CWT_DEVELOPMENT
#if (defined(CCTW) || defined(_WINDOWS))
    #include <windows.h>
#endif
#include <dos.h>
#include <compat.h>
#if (defined(MSC) || defined(__WATCOMC__) || defined(__HIGHC__))
    #include <conio.h>
#endif

#define CLOCK_RATE          1193182L
#define CLOCKS_PER_SECOND   18.206481934
#define PORTB               0X61
#define CMD8253             0X43
#define CH0_8253            0X40
#define CH2_8253            0X42
#define LOW_TIME            0X46C
#define HIGH_TIME           0X46E

void set_sound_off(void);

short set_sound_on(unsigned short pitch, unsigned short duration)
{
    union REGS regs;
    unsigned short s_count, count;

    /* CONFIRM VALID PITCH */
    if (pitch <= 0) return (-1);

    pitch = (unsigned) (CLOCK_RATE/pitch);
    /* CONVERT DURATION TO CLOCK TICKS */
    if (duration) duration = (unsigned short) (duration*18206L/1000000L);

    outp(PORTB, inp(PORTB) | 3);       /* send byte to port b */
    outp(CMD8253, 0XB6);    /* set up I/O register (10110110) */
    outp(CH2_8253, pitch & 0XFF);      /* send counter to latch */
    outp(CH2_8253, pitch >> 8);

    /* IF SPECIFIC TIME INTERVAL NOT REQUESTED (i.e. continuous sound) */
    if (duration) {
        setwordreg(ax) = 0;                     /* get time service */
        int86(0X1A, &regs, &regs);
        s_count = setwordreg(dx);               /* low part of timer count */
        do {
            setwordreg(ax) = 0;                 /* get time service */
            int86(0X1A, &regs, &regs);
            count = setwordreg(dx);             /* low part of timer count */
        } while (count < duration+s_count);
    }
    if (duration) set_sound_off();

    return (0);
}


void set_sound_off(void)
{
    /* TURN OFF THE SOUND (CLEAR LOW 2 BITS) */
    outp(PORTB, inp(PORTB) & 0XFC);

    /* RESTORE ORIGINAL COUNTER VALUE */
    outp(CMD8253, 0XB6);      /* set up I/O register (10110110) */
    outp(CH2_8253, 0);           /* send counter to latch */
    outp(CH2_8253, 0);
}


void key_click(void)
{
	set_sound_on(10, 55);
}