Simple signal generator source program

#include
#define DA0832 XBYTE[0Xa000]
#define uchar unsigned char
#define S1 XBYTE[0X0000]
#define S2 XBYTE[0X2000]
#define S3 XBYTE[0X4000]
uchar code tab[10]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f};
uchar code tosin[256]={0x80,0x83,0x86,0x89,0x8d,0x90,0x93,0x96,0x99,0x9c,0x9f,0xa2,0xa5,0xa8,0xab,0xae,0xb1,0xb4,0xb7,0xba,0xbc,0xbf,0xc2,0xc5
,0xc7,0xca,0xcc,0xcf,0xd1,0xd4,0xd6,0xd8,0xda,0xdd,0xdf,0xe1,0xe3,0xe5,0xe7,0xe9,0xea,0xec,0xee,0xef,0xf1,0xf2,0xf4,0xf5
,0xf6,0xf7,0xf8,0xf9,0xfa,0xfb,0xfc,0xfd,0xfd,0xfe,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xfe,0xfd
,0xfd,0xfc,0xfb,0xfa,0xf9,0xf8,0xf7,0xf6,0xf5,0xf4,0xf2,0xf1,0xef,0xee,0xec,0xea,0xe9,0xe7,0xe5,0xe3,0xe1,0xde,0xdd,0xda
,0xd8,0xd6,0xd4,0xd1,0xcf,0xcc,0xca,0xc7,0xc5,0xc2,0xbf,0xbc,0xba,0xb7,0xb4,0xb1,0xae,0xab,0xa8,0xa5,0xa2,0x9f,0x9c,0x99
,0x96,0x93,0x90,0x8d,0x89,0x86,0x83,0x80,0x80,0x7c,0x79,0x76,0x72,0x6f,0x6c,0x69,0x66,0x63,0x60,0x5d,0x5a,0x57,0x55,0x51
,0x4e,0x4c,0x48,0x45,0x43,0x40,0x3d,0x3a,0x38,0x35,0x33,0x30,0x2e,0x2b,0x29,0x27,0x25,0x22,0x20,0x1e,0x1c,0x1a,0x18,0x16
,0x15,0x13,0x11,0x10,0x0e,0x0d,0x0b,0x0a,0x09,0x08,0x07,0x06,0x05,0x04,0x03,0x02,0x02,0x01,0x00,0x00,0x00,0x00,0x00,0x00
,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x02 ,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0a,0x0b,0x0d,0x0e,0x10,0x11,0x13,0x15
,0x16,0x18,0x1a,0x1c,0x1e,0x20,0x22,0x25,0x27,0x29,0x2b,0x2e,0x30,0x33,0x35,0x38,0x3a,0x3d,0x40,0x43,0x45,0x48,0x4c,0x4e
,0x51,0x55,0x57,0x5a,0x5d,0x60,0x63,0x66 ,0x69,0x6c,0x6f,0x72,0x76,0x79,0x7c,0x80 };
uchar fun=0,b=0,c=0,d=0,tl,th;

void key1(void);
void key2(void);
void key3(void);
void key4(void);
void judge(void);

void main(void)
{
TMOD=0X01;
TR0=1;
th=0xff;
tl=0xd0;
TH0=th;
TL0=tl;
ET0=1;
EA=1;
while(1)
{
judge();
}
}

void judge(void)
{
uchar line,row,de1,de2,keym;
P1=0x0f;
keym=P1;
if(keym==0x0f)return;
for(de1=0;de1<200;de1++)
for(de2=0;de2<125;de2++){;}
P1=0x0f;
keym=P1;
if(keym==0x0f)return;
P1=0x0f;
line=P1;
P1=0xf0;
row=P1;
line=line+row;/*存放特征键值*/

if(line==0xde)key1();
if(line==0x7e)key2();
if(line==0xbd)key3();
if(line==0x7d)key4();
}

void key1(void) //Key 1 selects the wave type, 1 is sine wave, 2 is triangle wave, 3 is square wave
{
fun++;
if(fun==4)fun=0x00;

}

void key2(void) //2nd key to increase frequency
{
tl++;
if(tl==0x1f)th++;
}
void key3(void) //3rd key to decrease frequency
{
tl--;
if(tl==0x00)th--;
}

void key4(void) //4-key display frequency
{
double t;
int f;
TR0=0;//Difference of ＥＴ０
t=(65535-th*256-tl)*0.4;
f=(int)(1000/t);
S3=tab[f%10];
f=f/10;
S2=tab[f%10];
f=f/10;
if(f==0)S1=0;
else S1=tab[f];
TR0=1;
}

void time0_int(void) interrupt 1 //interrupt service routine
{
TR0=0;
if(fun==1)
{
DA0832=tosin; //sine wave
b++;
}
else if(fun==2) //triangle wave
{
if(c<128)DA0832=c;
else DA0832=255-c;
c++;
}
else if(fun==3) //square wave
{
d++;
if(d<=128)DA0832=0x00;
else DA0832=0xff;
}
TH0=th;
TL0=tl;
TR0=1;
}