ds_12887.c

Realtime clock DS12c887

/*========= DS 12887 RTC chip routines ========
* All required rotuines for the RTC chip.
* The Chip is used in non-multiplexed mode.
* All the control signals are generated by port bits as per the 
  timing diagram in data sheet.
* The Intel Timing logic is used 
==============================================*/



/*==============Include Files =================*/

#include <reg52.h>
#include <stdio.h>
#include <DS_12887.h>

/*============== Bit Defines ==================*/

sbit RTC_AS   = P1^1;                            // Address Latch
sbit RTC_RW   = P1^2;                            // Read !Write
sbit RTC_DS   = P1^3;                            // Data Select
sbit RTC_CS   = P1^4;                            // !Chip Select;

sbit Min_Adj     = P2^5;                         // IncPB
sbit Hour_Adj    = P2^6;                         // DecPB
sbit Set_Clk     = P2^7;                         // EnterPB

bit  F_Clk_Adj = 0;

extern unsigned int hour, minute, second ;
extern unsigned char  string[32];

/*=============================================*/

#define     RTC_PORT     P3                       // P3 connected to RTC ( 1 byte )
sfr         P3MDOUT  =   0xA7 ;

/*==========Function Prototypes ===============*/

void RTC_Byte_Wr(unsigned char, unsigned char);
unsigned char RTC_Byte_Rd (unsigned char);
void RTC_Init (void);
unsigned int BCDtoBin(unsigned char);
unsigned int BinToBCD(unsigned char);
extern void display(char *);

/*=============================================*/

/*=============================================*/

 unsigned char RTC_Byte_Rd ( unsigned char address)
 {
   unsigned char RdByte;

   P3MDOUT = 0xFF;
   RTC_DS  = 1;
   RTC_RW  = 1;
   RTC_CS  = 0;
   RTC_AS  = 1;
   P3      = address;
   RTC_AS  = 0;                                  // Latch the address
   RTC_DS  = 0;
   P3MDOUT = 0x00;
   RdByte  = P3;
   RTC_DS  = 1;                                  // Read the data from RTC into P3
   P3MDOUT = 0xFF;
   RTC_CS  = 1;
   return RdByte;
}

/*===============================================*/

void RTC_Byte_Wr(unsigned char address, unsigned char byte)
{
   
   P3MDOUT = 0xFF;
   RTC_DS  = 1;
   RTC_RW  = 1;
   RTC_CS  = 0;
   RTC_AS  = 1;
   P3      = address;
   RTC_AS  = 0;                                  // Latch the address
   RTC_RW  = 0;
   P3      = byte;
   RTC_RW  = 1;                                  // Write the data into RTC
   RTC_CS  = 1;

 }

 /*===============================================*/

 void RTC_Init (void)
 {
   RTC_Byte_Wr ( REGA, 0x24);                    // A.0=A.1=A.2=A.3 = 0 for 2Hz sq.wave
                                                 // A.4=0,A.5=1,A.6=0 for Osc. On
   RTC_Byte_Wr ( REGB, 0x0A);                    // B.1=1 for 24Hr mode;
                                                 // B.2=0 for BCD mode;
												 // B.3=0 Sq Wave enab.
 }

 /*===============================================*/

 void ReadTime (void)
 {
   RTC_Byte_Wr ( REGB, 0x8A);                    // Stop clock register updates

   hour   = BCDtoBin ( RTC_Byte_Rd (CLK_HR));
   minute = BCDtoBin ( RTC_Byte_Rd (CLK_MIN));
   second = BCDtoBin ( RTC_Byte_Rd (CLK_SEC));

   RTC_Byte_Wr ( REGB, 0x0A);                   // Restart clock register update

 }

 /*==============================================*/

 void set_CurrentTime (void)
 {
   if (Min_Adj == 0 )		                     // User has pressed the Min PB
     {
	   F_Clk_Adj = 1;                            // Stop clock updates in MAIN..
         
		 if ( minute < 60 )
		    {
			  ++ minute;
			  sprintf(string, "TimeSet Min :%02u ", minute );                 
              display(string);				     // Display the modified time
			}
		  else 
		    {
			  minute = 0;						 // If minute value > 59, then 0
			}  	   
	 }
//==============================================

	if (Hour_Adj == 0 )
	  {
        F_Clk_Adj = 1;

          if ( hour < 24 )
		    {
			  hour++;
			  sprintf(string, "TimeSet Hour: %02u ", hour);
			  display(string);
		    }
	      else 
		   {
		      hour = 0;
		   }
	 }

//=============================================

   	if ( Set_Clk == 0 )
	  {
	    F_Clk_Adj = 1;
		RTC_Byte_Wr ( REGB, 0x8A);                  // Stop clock register updates 

		RTC_Byte_Wr ( CLK_SEC, 0);
		RTC_Byte_Wr ( CLK_MIN, BinToBCD (minute));
		RTC_Byte_Wr ( CLK_HR, BinToBCD (hour));

		RTC_Byte_Wr ( REGB, 0x0A);                  // Start clock register updates
		F_Clk_Adj = 0;
      }
}

/*=============================================*/

unsigned int BCDtoBin(unsigned char val)		 // To read from RTC.
{
   val -= (val/0x10)*0x06;
   return val;
}

/*=============================================*/

unsigned int BinToBCD(unsigned char temp) 	     // To write to RTC
{
   temp += (temp/0x0A)*0x06;
   return temp;
} 

/*=============================================*/