测量NE555产生方波频率时，用跳帽将J13中的NAL与P34短接，NE555发生的信号输入到单片机的P34引脚，即单片机的T0引脚，该信号的频率大小可以通过Rb3可调电位器改变

代码：

 #include "reg52.h"
#include "absacc.h"unsigned char code SMG_DM_NoDot[18]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90,0x88,0x80,0xc6,0xc0,0x86,0x8e,0xbf,0x7f};unsigned int count_f = 0;
unsigned char count_t = 0;
unsigned int dat_f = 0;void DelaySMG(unsigned int t)
{while(t--);
}void DisplaySMG_Bit(unsigned char pos, unsigned char value)
{XBYTE[0xE000] = 0xFF;XBYTE[0xC000] = 0x01 << pos;XBYTE[0xE000] = value;
}void DisplaySMG_F()
{DisplaySMG_Bit(0, SMG_DM_NoDot[15]);DelaySMG(500);if(dat_f > 9999)DisplaySMG_Bit(3, SMG_DM_NoDot[dat_f / 10000]);DelaySMG(500);if(dat_f > 999)DisplaySMG_Bit(4, SMG_DM_NoDot[(dat_f / 1000) % 10]);DelaySMG(500);if(dat_f > 99)DisplaySMG_Bit(5, SMG_DM_NoDot[(dat_f / 100) % 10]);DelaySMG(500);if(dat_f > 9)DisplaySMG_Bit(6, SMG_DM_NoDot[(dat_f / 10) % 10]);DelaySMG(500);DisplaySMG_Bit(7, SMG_DM_NoDot[dat_f % 10]);DelaySMG(500);
}void Init_Timer()
{TH0 = 0xff;        TL0 = 0xff;TH1 = (65536 - 50000) / 256;        TL1 = (65536 - 50000) % 256;TMOD = 0x16;     //定时器1用方式1，定时；定时器0用方式2，计数，对应那个表看ET0 = 1;ET1 = 1;EA = 1;TR0 = 1;TR1 = 1;
}void Service_T0() interrupt 1
{count_f++;
}void Service_T1() interrupt 3
{TH1 = (65536 - 50000) / 256;        TL1 = (65536 - 50000) % 256;count_t++;if(count_t == 20){dat_f = count_f;count_f = 0;count_t = 0;}
}void main()
{Init_Timer();XBYTE[0x8000] = 0xff;XBYTE[0xA000] = 0x00;	while(1){DisplaySMG_F();}
}