重新设计这段单片机程序，采用定时器中断轮询的机制来判断是否有按键按下，并实现同样功能。

Question

例程:
#include<reg51.h>
#define uchar unsigned char
#define uint unsigned int
uchar code DSY_CODE[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90,
0x88,0x83,0xc6,0xa1,0x86,0x8e,0x00};
sbit BEEP=P3^7;

uchar Pre_KeyNo=16,KeyNo=16;

void DelayMS(uint x)
{
uchar i;
while(x--) for(i=0;i<120;i++);
}

void Keys_Scan()
{
uchar Tmp;
P1=0x0f;
DelayMS(1);
Tmp=P1^0x0f;
switch(Tmp)
{
case 1: KeyNo=0;break;
case 2: KeyNo=1;break;
case 4: KeyNo=2;break;
case 8: KeyNo=3;break;
default:KeyNo=16;
}
P1=0xf0;
DelayMS(1);
Tmp=P1>>4^0x0f;

switch(Tmp)
{
case 1: KeyNo+=0;break;
case 2: KeyNo+=4;break;
case 4: KeyNo+=8;break;
case 8: KeyNo+=12;
}
}

void Beep()
{
uchar i;
for(i=0;i<100;i++)
{
DelayMS(1);
BEEP=~BEEP;
}
BEEP=0;
}
/
void main()
{
P0=0x00;
BEEP=0;
while(1)
{
P1=0xf0;
if(P1!=0xf0) Keys_Scan();
if(Pre_KeyNo!=KeyNo)
{
P0=~DSY_CODE[KeyNo];
Beep();
Pre_KeyNo=KeyNo;
}
DelayMS(100);
}
}

Answer 1

#include<reg51.h>
#define uchar unsigned char
#define uint unsigned int
uchar code DSY_CODE[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90,
0x88,0x83,0xc6,0xa1,0x86,0x8e,0x00};
sbit BEEP=P3^7;
bit flag=0;
uchar Pre_KeyNo=16,KeyNo=16;
void DelayMS(uint x)
{
uchar i;
while(x--) for(i=0;i<120;i++);
}
void void t0isr() interrupt 1
{
uchar Tmp;
P1=0x0f;
DelayMS(1);
Tmp=P1^0x0f;
switch(Tmp)
{
case 1: KeyNo=0;break;
case 2: KeyNo=1;break;
case 4: KeyNo=2;break;
case 8: KeyNo=3;break;
default:flag=1;break;
}
P1=0xf0;
DelayMS(1);
Tmp=P1>>4^0x0f;
switch(Tmp)
{
case 1: KeyNo+=0;break;
case 2: KeyNo+=4;break;
case 4: KeyNo+=8;break;
case 8: KeyNo+=12;
default:flag=1;break;
}
}
void Beep()
{
uchar i;
for(i=0;i<100;i++)
{
DelayMS(1);
BEEP=~BEEP;
}
BEEP=0;
}
/
void main()
{
TMOD=0x01;
TH0=(65536-10000)/256;
TL0=(65536-10000)%256;
TR0=1;
ET0=1;
EA=1;
P0=0x00;
BEEP=0;
while(1)
{
if(flag)
{
flag=0;
P0=~DSY_CODE[KeyNo];
Beep();
Pre_KeyNo=KeyNo;
}
DelayMS(100);
}
}