為什么我的數碼管不能一直保持顯示，總是一閃一閃的？程序如下：
#include<reg51.h>
#define uchar unsigned char
#define uint unsigned int
sbit P10=P1^0;
sbit P11=P1^1;
sbit P12=P1^2;
sbit P13=P1^3;
sbit P14=P1^4;
sbit P15=P1^5;
sbit P16=P1^6;
sbit P17=P1^7;
sbit P20=P2^0;
sbit P21=P2^1;
sbit P22=P2^2;
sbit P23=P2^3;
sbit P24=P2^4;
sbit P25=P2^5;
sbit P26=P2^6;
sbit P27=P2^7;
sbit key1=P3^2;
sbit key2=P3^3;
uchar flag;
void key_scan(void);
void xianshi(void);
void tingzhi(void);
void delay5ms()
{
uchar i,j;
for(i=10;i>0;i--)
for(j=248;j>0;j--);
}
void key_scan()
{
if(key1==0)
{
delay5ms();
if(key1==0)
{
flag=1;
while(key1==1)
delay5ms();
}
}
if(key2==0)
{
delay5ms();
if(key2==0)
{
flag=2;
while(key2==1)
delay5ms();
}
}
}
void xianshi()
{
P10=1; //上面數碼管顯示
P0=0x89;
delay5ms();
P0=0xff;
P11=1;
P10=0;
P0=0x88;
delay5ms();
P0=0xff;
P11=0;
P12=1;
P0=0x8c;
delay5ms();
P0=0xff;
P12=0;
P13=1;
P0=0x8c;
delay5ms();
P0=0xff;
P13=0;
P14=1;
P0=0x91;
delay5ms();
P0=0xff;
P14=0;
P20=1; //下面數碼管顯示
P0=0x83;
delay5ms();
P0=0xff;
P21=1;
P20=0;
P0=0xf9;
delay5ms();
P0=0xff;
P21=0;
P22=1;
P0=0x8d;
delay5ms();
P0=0xff;
P22=0;
P23=1;
P0=0x87;
delay5ms();
P0=0xff;
P23=0;
P24=1;
P0=0x89;
delay5ms();
P0=0xff;
P24=0;
P25=1;
P0=0xa1;
delay5ms();
P0=0xff;
P25=0;
P26=1;
P0=0x88;
delay5ms();
P0=0xff;
P26=0;
P27=1;
P0=0x91;
delay5ms();
P0=0xff;
P27=0;
}
void tingzhi()
{
P0=0xff;
P1=0;
P2=0;
flag=0;
}
void main()
{
P0=0xff;
P1=0;
P2=0;
flag=0;
while(1)
{
key_scan();
switch(flag)
{
case 1:xianshi();break;
case 2:tingzhi();break;
}
}
}
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