DS1318与8051微控制器的接口

本应用笔记演示了使用DS1318历时计数器计算天数。软件实例中包括基本的操作程序，并给出了应用电路的原理图。



计数器概述

该应用笔记演示了如何使用DS1318历时计数器，DS1318具有44位计数器，可提供244μs的计时分辨率。44位计数器通过6个8位寄存器(图1)进行访问。



从概念上来说，44位计数器可以分成一个12位亚秒级计数器和一个分辨率为一秒的32位计数器(图2)。如果应用种不需要亚秒级分辨率，则可访问32位秒计数器。



在本应用笔记提供的示例中，软件子程序每秒一次连续读取32位秒计数器的数值，并通过8051微控制器(μC)的UART接口以ASCII码格式输出时间和日期。时间和日期基于从1970年1月1日，00:00:00起所经历的时间，单位为秒。00000000h对应的时间是1970年1月1日，00:00:00；42C924C0h对应的时间为2005/7/4 12:00:00。

另一子程序将器件配置成频率为1Hz的周期性中断，每次发生中断，中断处理程序读取计数器数据，将时间转换成日期格式，并通过URAT以ASCII格式输出数据。
我们还提供其它例程，在其它例程中可以对DS1318进行以下操作：可以将用户输入数据写入寄存器；将用户输入的时间和日期转换成自1970年1月1日起所经历的时间，单位为秒；向计数器写入数据。另一子程序用于读取DS1318寄存器，并以十六进制格式输出数据。

工作原理

本应用笔记中的硬件电路将DS1318的数据放入μC的数据存储空间。μC通过读、写正确地址的数据存储器访问DS1318寄存器。

本实例中采用DS80C323低电压、8051兼容微控制器。用户输入数据和程序输出数据都将传递到μC，通过PC终端仿真器的RS-232接口进行通信。有关本应用笔记中DS80C323微控制器的详细信息可从公司网站下载。

程序如下：

Figure 3. Program Listing /*********************************************************************/
/* Ds1318AN.c program, use on the DS1318 app note board              */
/*********************************************************************/
#include   /* Prototypes for I/O functions           */
#include   /* Register declarations for DS5000       */
#include   /* needed to define xdata addresses       */
/***************************** Defines *******************************/
#define SSEC1 XBYTE
#define SSEC2 XBYTE
#define SEC0 XBYTE
#define SEC1 XBYTE
#define SEC2 XBYTE
#define SEC3 XBYTE
#define AL0 XBYTE
#define AL1 XBYTE
#define AL2 XBYTE
#define AL3 XBYTE
#define CTLA XBYTE
#define CTLB XBYTE
#define STAT XBYTE
/************************* bit definitions ***************************/
/************************* Global Variables **************************/
uchar int_flg = 0;
/*********************** Function Prototypes *************************/
void init_rtc();
void writebyte();
void readregs();
void disp_clk_regs();
void disp_clk_regs_int();
void bin2date();
unsigned long date2bin(uint, uint, uint, uint, uint, uint);
void external0_int(void);
void init_rtc() /* ------------ set the time and date ----------------- */
/* Note: NO error checking is done on the user entries! */
{
uint yrs, mon, dt, hrs, min, sec;
unsigned long y;
printf("\nEnter the year (1970-2099): ");
scanf("%d", &yrs);
printf("Enter the month (1-12): ");
scanf("%d", &mon);
printf("Enter the date (1-31): ");
scanf("%d", &dt);
printf("Enter the hour (0-23): ");
scanf("%d", &hrs);
printf("Enter the minute (0-59): ");
scanf("%d", &min);
printf("Enter the second (0-59): ");
scanf("%d", &sec);
CTLA = 0x46; /* disable update transfers */
y = date2bin(yrs, mon, dt, hrs, min, sec);
SEC0 = (y & 0xff);
SEC1 = ((y >> 8) & 0xff);
SEC2 = ((y >> 16) & 0xff);
SEC3 = ((y >> 24) & 0xff);
CTLA = 0xC6;
}
void writebyte() /* -------- enter data for one byte --------- */
{
int add;
uchar dat;
printf("\nEnter address (hex): ");
scanf("%x", &add);
printf("Enter data (hex): ");
scanf("%bx", &dat);
XBYTE = dat;
}
void readregs() /* --------- list all of the registers -------- */
{
uchar inc;
CTLA = 0x46; /* disable update transfers */
printf("\n");
for(inc = 0; inc < 0xd; inc++)
{
  printf("%02bx ", XBYTE);
}
CTLA = 0xC6; /* enable transfers, osc, sqw */
}
void disp_clk_regs()  /* -------------- read time & date using TE as intended ----------------- */
{
uchar prv_sec = 99;
while(!RI) /* Read & Display Clock Registers */
{
  if(prv_sec != SEC0) /* display once per second */
  {
   bin2date();
   prv_sec = SEC0;
  }
}
  RI = 0;  /* Swallow keypress to exit loop */
}
void disp_clk_regs_int()  /* ----- display time using irq output ----- */
{
CTLA = 0xC6; /* enable update transfers, oscillator, squarewave and PIE */
CTLB = 0xA0; /* PF = 1Hz, SQW = 32kHz */
EX0 = 1; /* enable interrupt 0 */
IT0 = 1; /* edge activated */
PX0 = 0; /* low priority */
EX1 = 0; /* disable interrupt 1 */
EA = 1; /* enable all interrupts */
while(!RI) /* Read & Display Clock Registers */
{
  while(!int_flg); /* wait for interrupt */
  if(int_flg & 0x02) /* only display if the periodic flag caused the interrupt */
  {
   EX0 = EX1 = 0; /* disable interrupts while updating the display */
   bin2date();  /* calculate and display time and date */
   int_flg = 0;  /* for this example, we'll just clear all interrupt sources */
   EX0 = EX1 = 1; /* re-enable interrupts */
  }
}
EX0 = 0;  /* disable interrupt */
RI = 0;    /* Swallow keypress to exit loop */
}
/* Note: The following routine could be replaced with the ANSI C ctime function */
void bin2date() /* ------ convert binary time to date format ------ */
{
int yrs, mon, day, date, dow, tmp, jday, hrs, min, sec;
uchar ssec;
unsigned long x, j, n;
CTLA = 0x46; /* disable update transfers */
x = SEC3;
x <<= 8;
x |= SEC2;
x <<= 8;
x |= SEC1;
x <<= 8;
x |= SEC0;
ssec = SSEC2;
CTLA = 0xC6; /* enable transfers, osc, sqw */
j = x / 60;   /* whole minutes since 1/1/70 */
sec = x - (60 * j);  /* leftover seconds */
n = j / 60;
min = j - (60 * n);
j = n / 24;
hrs = n - (24 * j);
j = j + (365 + 366);  /* whole days since 1/1/68 */
day = j / ((4 * 365) + 1);
tmp = j % ((4 * 365) + 1);
if(tmp >= (31 + 29))  /* if past 2/29 */
  day++;   /* add a leap day */
yrs = (j - day) / 365;  /* whole years since 1968 */
jday = j - (yrs * 365) - day; /* days since 1/1 of current year */
if(tmp <= 365 && tmp >= 60)  /* if past 2/29 and a leap year then */
  jday++;   /* add a leap day */
yrs += 1968;    /* calculate year */
for(mon = 12; mon > 0; mon--)
{
  switch(mon)
  {
   case 1: tmp = 0; break;
   case 2: tmp = 31; break;
   case 3: tmp = 59; break;
   case 4: tmp = 90; break;
   case 5: tmp = 120; break;
   case 6: tmp = 151; break;
   case 7: tmp = 181; break;
   case 8: tmp = 212; break;
   case 9: tmp = 243; break;
   case 10: tmp = 273; break;
   case 11: tmp = 304; break;
   case 12: tmp = 334; break;
  }
  if((mon > 2) && !(yrs % 4)) /* adjust for leap year */
   tmp++;
  if(jday >= tmp) break;
}
day = jday - tmp + 1; /* calculate day in month */
dow = (j + 1) % 7 + 1; /* 1 = Sun, 2 = Mon, and so on */
printf("\n%04d/%02d/%02d %d %02d:%02d:", yrs ,mon, day, dow, hrs, min);
printf("%02d.%02bu", sec, ssec);
}
/* ---- convert date to elapsed days in binary ---- */
unsigned long date2bin(uint yrs, uint mon, uint day, uint hrs, uint min, uint sec)
{
unsigned long x;
/* the following is broken down for clarity */
x = 365 * (yrs - 1970);   /* calculate number of days for previous years */
x += (yrs - 1969) >> 2;   /* add a day for each leap year */
if((mon > 2) && (yrs % 4 == 0))  /* add a day if current year is leap and past Feb 29th */
  x++;
switch(mon)
{
  case 1: x += 0; break;
  case 2: x += 31; break;
  case 3: x += 59; break;
  case 4: x += 90; break;
  case 5: x += 120; break;
  case 6: x += 151; break;
  case 7: x += 181; break;
  case 8: x += 212; break;
  case 9: x += 243; break;
  case 10: x += 273; break;
  case 11: x += 304; break;
  case 12: x += 334; break;
}
x += day - 1;   /* finally, add the days into the current month */
x = x * 86400;  /* and calculate the number of seconds in all those days */
x += ((long) hrs * 3600); /* add the number of seconds in the hours */
x += (min * 60);  /* ditto the minutes */
x += sec;   /* finally, the seconds */
return(x);
}
void external0_int(void) interrupt 0 /* --- display time/date on interrupt from RTC --- */
{
EX0 = EX1 = 0; /* disable interrupt */
int_flg = STAT; /* clear the interrupt source, save the info */
STAT = 0;  /* clear PF (and all other bits) */
EX0 = EX1 = 1; /* re-enable interrupt */
}
main (void)  /* ----------------------------------------------------- */
{
uchar i, M, M1;
while (1)
{
printf("\nDS1318  build %s\n", __DATE__);
printf("CI Clock Init CN Clk iNt rd\n");
printf("CR Read Time   W Write byte\n");
printf("R  Read regs\n");
printf("Enter Menu Selection:");
M = _getkey();
switch(M)
{
  case 'C':
  case 'c':
  printf("\rEnter Clock Routine to run: C");
  M1 = _getkey();
  switch(M1)
  {
   case 'I':
   case 'i': init_rtc(); break;
   case 'N':
   case 'n': disp_clk_regs_int(); break;
   case 'R':
   case 'r': disp_clk_regs(); break;
  }
  break;
  case 'R':
  case 'r': readregs(); break;
  case 'W':
  case 'w': writebyte(); break;
}
   }
}


电路原理图见PDF附件。

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