第22章 系统时间(RTC编程)

取得当前系统时间的方法是直接访问RTC芯片。

RTC芯片可以通过0x70和0x71端口直接访问。0x70是选址寄存器，0x71是数据寄存器。

Addr Function
==== =========================================
** clock/calendar

00 current second for real-time clock
01 alarm second
02 current minute
03 alarm minute
04 current hour
05 alarm hour
06 current day of week (1=Sunday)
07 current date of month
08 current month
09 current year (final two digits; eg, 93)

rtc.h源代码如下所示

#ifndef _RTC_H_#define _RTC_H_#define RTC_REG_ADDR    0x70    //寻址寄存器#define RTC_REG_VALUE    0x71    //内容寄存器#define SECOND_REG    0x0#define MINUTE_REG    0x2#define HOUR_REG    0x4#define DAY_WEEK_REG    0x6#define DAY_MONTH_REG    0x7#define MONTH_REG    0x8#define YEAR_REG    0x9void localtime();#endif

rtc.c源代码如下所示

#include "io.h"#include "rtc.h"#include "video.h"unsigned char get_second(){    outportb(RTC_REG_ADDR, SECOND_REG);    return inportb(RTC_REG_VALUE);    }unsigned char get_minute(){    outportb(RTC_REG_ADDR, MINUTE_REG);    return inportb(RTC_REG_VALUE);    }unsigned char get_hour(){    outportb(RTC_REG_ADDR, HOUR_REG);    return inportb(RTC_REG_VALUE);    }unsigned char get_week_day(){    outportb(RTC_REG_ADDR, DAY_WEEK_REG);    return inportb(RTC_REG_VALUE);    }unsigned char get_month_day(){    outportb(RTC_REG_ADDR, DAY_MONTH_REG);    return inportb(RTC_REG_VALUE);    }unsigned char get_month(){    outportb(RTC_REG_ADDR, MONTH_REG);    return inportb(RTC_REG_VALUE);    }unsigned char get_year(){    outportb(RTC_REG_ADDR, YEAR_REG);    return inportb(RTC_REG_VALUE);    }void localtime(){    unsigned char s,m,h,dw,dm,mm,y;    s = m = h = dw = dm = m = y = 0;    s = get_second();    m = get_minute();    h = get_hour();    dw = get_week_day();    dm = get_month_day();    mm = get_month();    y = get_year();    printf("20%x-%x-%x  %x  %x:%x:%x\n", y,mm,dm, dw, h,m,s);}