在C51程序设计中如何定义外部RAM或扩展IO端口的地址

分两种情况：

外部RAM：在左侧项目窗口右键->options for target "xxxxx"->target页，有个off-chip xdata memery窗口，那里有ram的start和size，你可以根据你的硬件线路具体情况填写其实地址和RAM大小，注意都是16进制，然后在定义变量时，使用xdata描述，编译器就会自动把变量放到外部RAM区去了

扩展IO：

给你个例子：

unsigned char volatile xdata EX_IO _at_ 0xF000;表示这个IO口的地址是0xf000

试试看：

#include <reg51h>

#include <absacch>

#include <intrinsh>

#define uchar unsigned char

#define uint unsigned int

#define PA8255 0x8000

#define PB8255 0x8100

#define PC8255 0x8200

#define CTRL8255 0x8400

#define S1 (P1 = 0x28)

#define S2 (P0 = 0x51)

#define S3 (P0 = 0x82)

#define S4 (P0 = 0x15)

uchar code distab[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f};

char dispbuf[]={0x00,0x01,0x02,0x04};

uchar t50ms = 0;

uchar sec;

uchar SorT=0;

uchar WEorSN=0;

uchar time;

void INIT_TMR1 (void)

{

TMOD = 0x11;

TH0 =(65536-50000)/256;

TL0 =(65536-50000)%256;

EA = 1;

ET0 = 1;

TR0 = 1;

}

void TMR1_INT_SRV (void) interrupt 1

{

TH0 =(65536-50000)/256;

TL0 =(65536-50000)%256;

TF0 = 0;

sec=time;

if(++ t50ms == 20)

{

sec--;

t50ms = 0;

}

if(sec ==0 )

{

{

SorT ++;

}

if(SorT ==2)

{

sec = time;

WEorSN = !WEorSN;

SorT = 0;

}

}

}

void delay(uchar t)

{

uchar i;

for (;t>0;t--)

for (i=0;i<500;i++);

}

uchar keysearch(void)

{

uchar k;

XBYTE[CTRL8255]=0x81;

XBYTE[PA8255]=0x00;

k=XBYTE[PC8255];

k=~k;k=k&0x03;

return k;

}

void disp8255()

{

dispbuf[0]=distab[sec%10];

dispbuf[1]=distab[sec/10];

dispbuf[2]=distab[sec%10];

dispbuf[3]=distab[sec/10];

}

scankey(void)

{

uchar ta,tc,kr4,keynumb;

ta=keysearch();

if(ta==0)return 0x00;

else disp8255();

ta=keysearch();

if(ta==0)return 0x00;

else

{

ta=0xfe;

for(kr4=0;kr4<2;kr4++)

{

XBYTE[PA8255]=ta;

tc=XBYTE[PC8255];

if((tc&0x01)==0)keynumb=kr4+0;

if((tc&0x02)==0)keynumb=kr4+4;

if((tc&0x04)==0)keynumb=kr4+8;

ta<<=1;ta++;

}

}

return keynumb;

}

void main(void)

{

uchar a,b;

INIT_TMR1();

XBYTE[CTRL8255]=0x81;

delay(2);

while(1)

{

a=scankey();

delay(5);

b=scankey();

time=a10+b;

disp8255();

if( (SorT == 0)&&(WEorSN == 0) )

{

S1;

delay(2);

}

if( (SorT == 1)&(WEorSN == 0) )

{

S2;

delay(2);

}

if( (SorT == 0)&(WEorSN == 1) )

{

S3;

}

delay(2);

if( (SorT == 1)&(WEorSN == 1) )

{

S4;

delay(2);

}

}

}

1、 MOV R0，0

MOV DATA，#STRING

KKK：MOV A，R0

MOVC A，@A+DATA

INC R0

CJNE A，#24H，KKK

MOV NUM，R0

SJMP $

2、 MOV R0，LEN

MOV R1，#2

MOV A，#0

DDD：MOV 41H，@R1

INC R1

CJNE A，41H，NNN

JNC NNN

MOV A，41H

NNN：DJNZ R0，DDD

MOV MAX，A

SJMP $

//C51写的公历转农历和星期

#define uchar unsigned char

#define uint unsigned int

#include <intrinsh>

/

公历年对应的农历数据,每年三字节,

格式第一字节BIT7-4 位表示闰月月份,值为0 为无闰月,BIT3-0 对应农历第1-4 月的大小

第二字节BIT7-0 对应农历第5-12 月大小,第三字节BIT7 表示农历第13 个月大小

月份对应的位为1 表示本农历月大(30 天),为0 表示小(29 天)

第三字节BIT6-5 表示春节的公历月份,BIT4-0 表示春节的公历日期

/

code uchar year_code[597] = {

0x04,0xAe,0x53, //1901 0

0x0A,0x57,0x48, //1902 3

0x55,0x26,0xBd, //1903 6

0x0d,0x26,0x50, //1904 9

0x0d,0x95,0x44, //1905 12

0x46,0xAA,0xB9, //1906 15

0x05,0x6A,0x4d, //1907 18

0x09,0xAd,0x42, //1908 21

0x24,0xAe,0xB6, //1909

0x04,0xAe,0x4A, //1910

0x6A,0x4d,0xBe, //1911

0x0A,0x4d,0x52, //1912

0x0d,0x25,0x46, //1913

0x5d,0x52,0xBA, //1914

0x0B,0x54,0x4e, //1915

0x0d,0x6A,0x43, //1916

0x29,0x6d,0x37, //1917

0x09,0x5B,0x4B, //1918

0x74,0x9B,0xC1, //1919

0x04,0x97,0x54, //1920

0x0A,0x4B,0x48, //1921

0x5B,0x25,0xBC, //1922

0x06,0xA5,0x50, //1923

0x06,0xd4,0x45, //1924

0x4A,0xdA,0xB8, //1925

0x02,0xB6,0x4d, //1926

0x09,0x57,0x42, //1927

0x24,0x97,0xB7, //1928

0x04,0x97,0x4A, //1929

0x66,0x4B,0x3e, //1930

0x0d,0x4A,0x51, //1931

0x0e,0xA5,0x46, //1932

0x56,0xd4,0xBA, //1933

0x05,0xAd,0x4e, //1934

0x02,0xB6,0x44, //1935

0x39,0x37,0x38, //1936

0x09,0x2e,0x4B, //1937

0x7C,0x96,0xBf, //1938

0x0C,0x95,0x53, //1939

0x0d,0x4A,0x48, //1940

0x6d,0xA5,0x3B, //1941

0x0B,0x55,0x4f, //1942

0x05,0x6A,0x45, //1943

0x4A,0xAd,0xB9, //1944

0x02,0x5d,0x4d, //1945

0x09,0x2d,0x42, //1946

0x2C,0x95,0xB6, //1947

0x0A,0x95,0x4A, //1948

0x7B,0x4A,0xBd, //1949

0x06,0xCA,0x51, //1950

0x0B,0x55,0x46, //1951

0x55,0x5A,0xBB, //1952

0x04,0xdA,0x4e, //1953

0x0A,0x5B,0x43, //1954

0x35,0x2B,0xB8, //1955

0x05,0x2B,0x4C, //1956

0x8A,0x95,0x3f, //1957

0x0e,0x95,0x52, //1958

0x06,0xAA,0x48, //1959

0x7A,0xd5,0x3C, //1960

0x0A,0xB5,0x4f, //1961

0x04,0xB6,0x45, //1962

0x4A,0x57,0x39, //1963

0x0A,0x57,0x4d, //1964

0x05,0x26,0x42, //1965

0x3e,0x93,0x35, //1966

0x0d,0x95,0x49, //1967

0x75,0xAA,0xBe, //1968

0x05,0x6A,0x51, //1969

0x09,0x6d,0x46, //1970

0x54,0xAe,0xBB, //1971

0x04,0xAd,0x4f, //1972

0x0A,0x4d,0x43, //1973

0x4d,0x26,0xB7, //1974

0x0d,0x25,0x4B, //1975

0x8d,0x52,0xBf, //1976

0x0B,0x54,0x52, //1977

0x0B,0x6A,0x47, //1978

0x69,0x6d,0x3C, //1979

0x09,0x5B,0x50, //1980

0x04,0x9B,0x45, //1981

0x4A,0x4B,0xB9, //1982

0x0A,0x4B,0x4d, //1983

0xAB,0x25,0xC2, //1984

0x06,0xA5,0x54, //1985

0x06,0xd4,0x49, //1986

0x6A,0xdA,0x3d, //1987

0x0A,0xB6,0x51, //1988

0x09,0x37,0x46, //1989

0x54,0x97,0xBB, //1990

0x04,0x97,0x4f, //1991

0x06,0x4B,0x44, //1992

0x36,0xA5,0x37, //1993

0x0e,0xA5,0x4A, //1994

0x86,0xB2,0xBf, //1995

0x05,0xAC,0x53, //1996

0x0A,0xB6,0x47, //1997

0x59,0x36,0xBC, //1998

0x09,0x2e,0x50, //1999 294

0x0C,0x96,0x45, //2000 297

0x4d,0x4A,0xB8, //2001

0x0d,0x4A,0x4C, //2002

0x0d,0xA5,0x41, //2003

0x25,0xAA,0xB6, //2004

0x05,0x6A,0x49, //2005

0x7A,0xAd,0xBd, //2006

0x02,0x5d,0x52, //2007

0x09,0x2d,0x47, //2008

0x5C,0x95,0xBA, //2009

0x0A,0x95,0x4e, //2010

0x0B,0x4A,0x43, //2011

0x4B,0x55,0x37, //2012

0x0A,0xd5,0x4A, //2013

0x95,0x5A,0xBf, //2014

0x04,0xBA,0x53, //2015

0x0A,0x5B,0x48, //2016

0x65,0x2B,0xBC, //2017

0x05,0x2B,0x50, //2018

0x0A,0x93,0x45, //2019

0x47,0x4A,0xB9, //2020

0x06,0xAA,0x4C, //2021

0x0A,0xd5,0x41, //2022

0x24,0xdA,0xB6, //2023

0x04,0xB6,0x4A, //2024

0x69,0x57,0x3d, //2025

0x0A,0x4e,0x51, //2026

0x0d,0x26,0x46, //2027

0x5e,0x93,0x3A, //2028

0x0d,0x53,0x4d, //2029

0x05,0xAA,0x43, //2030

0x36,0xB5,0x37, //2031

0x09,0x6d,0x4B, //2032

0xB4,0xAe,0xBf, //2033

0x04,0xAd,0x53, //2034

0x0A,0x4d,0x48, //2035

0x6d,0x25,0xBC, //2036

0x0d,0x25,0x4f, //2037

0x0d,0x52,0x44, //2038

0x5d,0xAA,0x38, //2039

0x0B,0x5A,0x4C, //2040

0x05,0x6d,0x41, //2041

0x24,0xAd,0xB6, //2042

0x04,0x9B,0x4A, //2043

0x7A,0x4B,0xBe, //2044

0x0A,0x4B,0x51, //2045

0x0A,0xA5,0x46, //2046

0x5B,0x52,0xBA, //2047

0x06,0xd2,0x4e, //2048

0x0A,0xdA,0x42, //2049

0x35,0x5B,0x37, //2050

0x09,0x37,0x4B, //2051

0x84,0x97,0xC1, //2052

0x04,0x97,0x53, //2053

0x06,0x4B,0x48, //2054

0x66,0xA5,0x3C, //2055

0x0e,0xA5,0x4f, //2056

0x06,0xB2,0x44, //2057

0x4A,0xB6,0x38, //2058

0x0A,0xAe,0x4C, //2059

0x09,0x2e,0x42, //2060

0x3C,0x97,0x35, //2061

0x0C,0x96,0x49, //2062

0x7d,0x4A,0xBd, //2063

0x0d,0x4A,0x51, //2064

0x0d,0xA5,0x45, //2065

0x55,0xAA,0xBA, //2066

0x05,0x6A,0x4e, //2067

0x0A,0x6d,0x43, //2068

0x45,0x2e,0xB7, //2069

0x05,0x2d,0x4B, //2070

0x8A,0x95,0xBf, //2071

0x0A,0x95,0x53, //2072

0x0B,0x4A,0x47, //2073

0x6B,0x55,0x3B, //2074

0x0A,0xd5,0x4f, //2075

0x05,0x5A,0x45, //2076

0x4A,0x5d,0x38, //2077

0x0A,0x5B,0x4C, //2078

0x05,0x2B,0x42, //2079

0x3A,0x93,0xB6, //2080

0x06,0x93,0x49, //2081

0x77,0x29,0xBd, //2082

0x06,0xAA,0x51, //2083

0x0A,0xd5,0x46, //2084

0x54,0xdA,0xBA, //2085

0x04,0xB6,0x4e, //2086

0x0A,0x57,0x43, //2087

0x45,0x27,0x38, //2088

0x0d,0x26,0x4A, //2089

0x8e,0x93,0x3e, //2090

0x0d,0x52,0x52, //2091

0x0d,0xAA,0x47, //2092

0x66,0xB5,0x3B, //2093

0x05,0x6d,0x4f, //2094

0x04,0xAe,0x45, //2095

0x4A,0x4e,0xB9, //2096

0x0A,0x4d,0x4C, //2097

0x0d,0x15,0x41, //2098

0x2d,0x92,0xB5, //2099

};

///月份数据表

code uchar day_code1[9]={0x0,0x1f,0x3b,0x5a,0x78,0x97,0xb5,0xd4,0xf3};

code uint day_code2[3]={0x111,0x130,0x14e};

/

函数功能:输入BCD阳历数据,输出BCD阴历数据(只允许1901-2099年)

调用函数示例:Conversion(c_sun,year_sun,month_sun,day_sun)

如:计算2004年10月16日Conversion(0,0x4,0x10,0x16);

c_sun,year_sun,month_sun,day_sun均为BCD数据,c_sun为世纪标志位,c_sun=0为21世

纪,c_sun=1为19世纪

调用函数后,原有数据不变,读c_moon,year_moon,month_moon,day_moon得出阴历BCD数据

/

bit c_moon;

data uchar year_moon,month_moon,day_moon,week;

/子函数,用于读取数据表中农历月的大月或小月,如果该月为大返回1,为小返回0/

bit get_moon_day(uchar month_p,uint table_addr)

{

uchar temp;

switch (month_p)

{

case 1:{temp=year_code[table_addr]&0x08;

if (temp==0)return(0);else return(1);}

case 2:{temp=year_code[table_addr]&0x04;

if (temp==0)return(0);else return(1);}

case 3:{temp=year_code[table_addr]&0x02;

if (temp==0)return(0);else return(1);}

case 4:{temp=year_code[table_addr]&0x01;

if (temp==0)return(0);else return(1);}

case 5:{temp=year_code[table_addr+1]&0x80;

if (temp==0) return(0);else return(1);}

case 6:{temp=year_code[table_addr+1]&0x40;

if (temp==0)return(0);else return(1);}

case 7:{temp=year_code[table_addr+1]&0x20;

if (temp==0)return(0);else return(1);}

case 8:{temp=year_code[table_addr+1]&0x10;

if (temp==0)return(0);else return(1);}

case 9:{temp=year_code[table_addr+1]&0x08;

if (temp==0)return(0);else return(1);}

case 10:{temp=year_code[table_addr+1]&0x04;

if (temp==0)return(0);else return(1);}

case 11:{temp=year_code[table_addr+1]&0x02;

if (temp==0)return(0);else return(1);}

case 12:{temp=year_code[table_addr+1]&0x01;

if (temp==0)return(0);else return(1);}

case 13:{temp=year_code[table_addr+2]&0x80;

if (temp==0)return(0);else return(1);}

}

}

/

函数功能:输入BCD阳历数据,输出BCD阴历数据(只允许1901-2099年)

调用函数示例:Conversion(c_sun,year_sun,month_sun,day_sun)

如:计算2004年10月16日Conversion(0,0x4,0x10,0x16);

c_sun,year_sun,month_sun,day_sun均为BCD数据,c_sun为世纪标志位,c_sun=0为21世

纪,c_sun=1为19世纪

调用函数后,原有数据不变,读c_moon,year_moon,month_moon,day_moon得出阴历BCD数据

/

void Conversion(bit c,uchar year,uchar month,uchar day)

{ //c=0 为21世纪,c=1 为19世纪 输入输出数据均为BCD数据

uchar temp1,temp2,temp3,month_p;

uint temp4,table_addr;

bit flag2,flag_y;

temp1=year/16; //BCD->hex 先把数据转换为十六进制

temp2=year%16;

year=temp110+temp2;

temp1=month/16;

temp2=month%16;

month=temp110+temp2;

temp1=day/16;

temp2=day%16;

day=temp110+temp2;

//定位数据表地址

if(c==0)

{

table_addr=(year+0x64-1)0x3;

}

else

{

table_addr=(year-1)0x3;

}

//定位数据表地址完成

//取当年春节所在的公历月份

temp1=year_code[table_addr+2]&0x60;

temp1=_cror_(temp1,5);

//取当年春节所在的公历月份完成

//取当年春节所在的公历日

temp2=year_code[table_addr+2]&0x1f;

//取当年春节所在的公历日完成

// 计算当年春年离当年元旦的天数,春节只会在公历1月或2月

if(temp1==0x1)

{

temp3=temp2-1;

}

else

{

temp3=temp2+0x1f-1;

}

// 计算当年春年离当年元旦的天数完成

//计算公历日离当年元旦的天数,为了减少运算,用了两个表

//day_code1[9],day_code2[3]

//如果公历月在九月或前,天数会少于0xff,用表day_code1[9],

//在九月后,天数大于0xff,用表day_code2[3]

//如输入公历日为8月10日,则公历日离元旦天数为day_code1[8-1]+10-1

//如输入公历日为11月10日,则公历日离元旦天数为day_code2[11-10]+10-1

if (month<10)

{

temp4=day_code1[month-1]+day-1;

}

else

{

temp4=day_code2[month-10]+day-1;

}

if ((month>0x2)&&(year%0x4==0))

{ //如果公历月大于2月并且该年的2月为闰月,天数加1

temp4+=1;

}

//计算公历日离当年元旦的天数完成

//判断公历日在春节前还是春节后

if (temp4>=temp3)

{ //公历日在春节后或就是春节当日使用下面代码进行运算

temp4-=temp3;

month=0x1;

month_p=0x1; //month_p为月份指向,公历日在春节前或就是春节当日month_p指向首月

flag2=get_moon_day(month_p,table_addr);

//检查该农历月为大小还是小月,大月返回1,小月返回0

flag_y=0;

if(flag2==0)temp1=0x1d; //小月29天

else temp1=0x1e; //大小30天

temp2=year_code[table_addr]&0xf0;

temp2=_cror_(temp2,4); //从数据表中取该年的闰月月份,如为0则该年无闰月

while(temp4>=temp1)

{

temp4-=temp1;

month_p+=1;

if(month==temp2)

{

flag_y=~flag_y;

if(flag_y==0)

month+=1;

}

else month+=1;

flag2=get_moon_day(month_p,table_addr);

if(flag2==0)temp1=0x1d;

else temp1=0x1e;

}

day=temp4+1;

}

else

{ //公历日在春节前使用下面代码进行运算

temp3-=temp4;

if (year==0x0)

{

year=0x63;c=1;

}

else year-=1;

table_addr-=0x3;

month=0xc;

temp2=year_code[table_addr]&0xf0;

temp2=_cror_(temp2,4);

if (temp2==0)

month_p=0xc;

else

month_p=0xd; //

/month_p为月份指向,如果当年有闰月,一年有十三个月,月指向13,无闰月指向12/

flag_y=0;

flag2=get_moon_day(month_p,table_addr);

if(flag2==0)temp1=0x1d;

else temp1=0x1e;

while(temp3>temp1)

{

temp3-=temp1;

month_p-=1;

if(flag_y==0)month-=1;

if(month==temp2)flag_y=~flag_y;

flag2=get_moon_day(month_p,table_addr);

if(flag2==0)temp1=0x1d;

else temp1=0x1e;

}

day=temp1-temp3+1;

}

c_moon=c; //HEX->BCD ,运算结束后,把数据转换为BCD数据

temp1=year/10;

temp1=_crol_(temp1,4);

temp2=year%10;

year_moon=temp1|temp2;

temp1=month/10;

temp1=_crol_(temp1,4);

temp2=month%10;

month_moon=temp1|temp2;

temp1=day/10;

temp1=_crol_(temp1,4);

temp2=day%10;

day_moon=temp1|temp2;

}

/函数功能:输入BCD阳历数据,输出BCD星期数据(只允许1901-2099年)

调用函数示例:Conver_week(c_sun,year_sun,month_sun,day_sun)

如:计算2004年10月16日Conversion(0,0x4,0x10,0x16);

c_sun,year_sun,month_sun,day_sun均为BCD数据,c_sun为世纪标志位,c_sun=0为21世

纪,c_sun=1为19世纪

调用函数后,原有数据不变,读week得出阴历BCD数据

/

code uchar table_week[12]={0,3,3,6,1,4,6,2,5,0,3,5}; //月修正数据表

/

算法:日期+年份+所过闰年数+月较正数之和除7 的余数就是星期但如果是在

闰年又不到3 月份上述之和要减一天再除7

星期数为0

/

void Conver_week(bit c,uchar year,uchar month,uchar day)

{//c=0 为21世纪,c=1 为19世纪 输入输出数据均为BCD数据

uchar temp1,temp2;

temp1=year/16; //BCD->hex 先把数据转换为十六进制

temp2=year%16;

year=temp110+temp2;

temp1=month/16;

temp2=month%16;

month=temp110+temp2;

temp1=day/16;

temp2=day%16;

day=temp110+temp2;

if (c==0){year+=0x64;} //如果为21世纪,年份数加100

temp1=year/0x4; //所过闰年数只算1900年之后的

temp2=year+temp1;

temp2=temp2%0x7; //为节省资源,先进行一次取余,避免数大于0xff,避免使用整型数据

temp2=temp2+day+table_week[month-1];

if (year%0x4==0&&month<3)temp2-=1;

week=temp2%0x7;

}

//test

uchar c_sun,year_sun,month_sun,day_sun;

void main()

{

c_sun=1;

year_sun=0x2;

month_sun=0x11;

day_sun=0x3;

Conver_week(c_sun,year_sun,month_sun,day_sun);

Conversion(c_sun,year_sun,month_sun,day_sun);

while(1);

}

#include<reg51h>

sbit led=P1^0; //单片机管脚位声明

void main()

{

TMOD=0x01; //定时器TO工作在方式1

TH0=(65536-5000)/256; //装初值，12M晶振 1为1us; 5000为5000us=5ms；

TL0=(65536-5000)%256;

EA =1; //开总中断

ET0=1; //开定时器TO中断

TR0=1; //启动定时器

P1=0; //初始化P1口

while(1) ; //程序在这里等待中断发生

}

void T0_time() interrupt 1

{

unsigned char num;

TH0=(65536-5000)/256;

TL0=(65536-5000)%256;

num++;

if(num==100) //05S (1s闪烁1次==05S亮05S灭)

{

num=0;

led=~led; //led状态取反

}

}

这体现了嵌农和码农的价值观区别。

嵌农会精心计算一个变量的范围，而码农很少这么做，因为码农默认的数值类型一般是int32，可以满足日常范围需求，甚至像Python那样的语言自带大整数特性，根本不用考虑范围。然而嵌农呢，尤其是你说的c51，是个Intel祖传8位机，本来ram就很少，当然要精心考虑变量的大小了。像int32这样的东西太奢侈了，只能精打细算，根据现实情况精选一个范围合适的类型。鉴于大部分情况并不需要负数，所以用unsigned类型能提高0以上的数值范围。另外需要指出的是很多c51编译器里int类型是16位的。所以嵌农的悲伤就在这里，别人已经开始写算法了，你还在研究这个变量存不存得下的问题。

C51语言，由C语言继承而来的单片机编程语言。

和C语言不同的是，C51语言运行于单片机平台，而C语言则运行于普通的桌面平台。C51语言具有C语言结构清晰的优点，便于学习，同时具有汇编语言的硬件 *** 作能力。对于具有C语言编程基础的读者，能够轻松地掌握单片机C51语言的程序设计。

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