#include

#define uint unsigned int

#define uchar unsigned char

sbit k1=P3^2;

sbit k2=P3^3;

sbit bee=P1^2;

uchar PWM,num;

void delay(uchar z)

{

uchar i;

while(z--)

{

for(i=120;i>0;i--);

}

}

void spk()

{

bee=0;

delay(100);

bee=1;

delay(100);

}

void init_t0()

{

TMOD=0X01;

TH0=255;

TL0=256-PWM;

EA=1;

ET0=1;

TR0=1;

}

void key_scan()

{

while(k1==0)

{

if(PWM!=0XFF)

{

PWM++;

delay(10);

}

else

spk();

}

while(k2==0)

{

if(PWM!=0X01)

{

PWM--;

delay(10);

}

else

spk();

}

}

void main()

{

PWM=0X7f;

P2=0XFF;

init_t0();

while(1)

key_scan();

}

void t0() interrupt 1

{

num++;

TR0=0;

if(num%2==1)

{

P2=0;

TH0=0XFF;

TL0=256-PWM;

TR0=1;

}

if(num%2==0)

{

P2=0XFF;

TH0=0XFF;

TL0=PWM;

TR0=1;

}

}