Simple example of PIC16F84A reading clock chip DS1302

#include "delay.h"
#include "delay.c"
#include
#include

//Fuse configuration***********************************************************
__CONFIG(XT & WDTDIS & PWRTEN & PROTECT);

//Pin definition************************************************************
#define RS RB4 //Select register
#define EN RB5 //Signal enable

//Clock chip********************************************************
#define RST RA0 //Chip enable 
#define CLK RA1 //Chip clock
#define DAT RA2 //Chip data

//Display characters********************************************************
     unsigned char TopChar[] = {" "}; //Display buffer 
     unsigned char BotChar[] = {" "}; //

//********************************************************************
//Function name: portInit();
//Input parameters: None
//Output parameters: None
//Function description: Port settings
//Build date: 2008.12.12
//********************************************************************
void PortInit(void)
 {
     PORTA = 0x00; //Port settings 
     PORTB = 0x00; //
 
     TRISA = 0x00; //Direction settings   
     TRISB = 0x00; //

     OPTION = 0x00; //pull up to enable
 }

//*******************************************************************
//Function name: WriteData(data, rs);
//Input parameter: data to be written, 0 = instruction 1 = data 
//Output parameter: None
//Function description: Write 1602LCD
//Build date: 2008.12.12
//*******************************************************************
void WriteData(unsigned char data, unsigned char rs)
 {   
     RS = 0; //Assuming instruction

     if (rs & 0x01) RS = 1; //actual data

     PORTB = ((PORTB & 0xf0 ) | (data >> 4)); //Write high four bits    
     EN = 1; //Enable falling edge 
     EN = 0; //
     DelayUs(50); //
    
     PORTB = ((PORTB & 0xf0) | (data & 0x0f)); //Write low four bits
     EN = 1; //Enable falling edge 
     EN = 0; //                                            
     DelayUs(50); //
 }

//*******************************************************************
//Function name: AddrSite();
//Input parameter: coordinate parameter
//Output parameter: None
//Function description: Set the display address
//Construction date: 2008.12.12
//*******************************************************************
void AddrSite(unsigned char x, unsigned char y)
 {     
     if (y == 0) WriteData((0x80 | x), 0); //First row address
     
     else WriteData((0xc0 | x), 0); //Next row address 
 }

//*******************************************************************
//Function name: PrintChar(*s, len);
//Input parameters: buffer address, data length
//Output parameters: None
//Function description: string output display
//Construction date: 2008.12.12
//*******************************************************************
void PrintChar(unsigned char *s, unsigned char len)
 {   
     do //Loop sending                                      
     {
       WriteData(*s, 1); //Display character
       s++; //Next character
     }
     while (--len); //Display a line
 }

//*******************************************************************
//Function name: LcdInit();
//Input parameters: None
//Output parameters: None
//Function description: LCD initialization
//Construction date: 2008.12.12
//*******************************************************************
void LcdInit(void)
 {   
     unsigned char i = 3;

     RS = 0; //Select command
     PORTB = 0x03; //Interface settings

     do
     {
       EN = 1; // Enable falling edge 
       EN = 0; //
       DelayUs(50);      
     }
     while (--i); // Loop three times

     PORTB = 0x02; //Four-wire mode
     EN = 1; //Enable falling edge 
     EN = 0; //
     DelayUs(50);     

     WriteData(0x28, 0); //Interface settings
     WriteData(0x0c, 0); //Display open
     WriteData(0x01, 0); //Display clear
     WriteData(0x06, 0); //Address increment
 }

//*******************************************************************
//Function name: WriteByte(data);
//Input parameter: data to be written
//Output parameter: None
//Function description: Ds1302 write data
//Build date: 2008.12.12
//*******************************************************************
void WriteByte(unsigned char data)
 {
     unsigned char i;
     
     TRISA2 = 0; //Output direction
     i = 8; //Send eight bits    

     do
     {
       DAT = 0; //assumes it is false 
           
       if (data & 0x01) DAT = 1; //actually true
       
       CLK = 1; //clock rises
       data >>= 1; //shift right one bit
       CLK = 0; //clock clears
     }
     while (--i); //send in a loop  
 }

//*******************************************************************
//Function name: ReadByte();
//Input parameter: None
//Output parameter: Clock data
//Function description: Ds1302 read data
//Build date: 2008.12.12
//*******************************************************************
unsigned char ReadByte(void)
 {
     unsigned char i, data;
     
     TRISA2 = 1; //Input direction
     i = 8; //Collect eight bits

     do
     {
       data >>= 1; // data right shift

       if (DAT) data |= 0x80; //record one bit

       CLK = 1; //Clock set
       NOP();                   
       CLK = 0; //Clock falls
     }
     while (--i); //Loop receiving

     return data; //return data        
 }

//***********************************************************************
//Function name: WriteDs1302(addr, code);
//Input parameters: register address, instruction
//Output parameters: None
//Function description: Ds1302 write operation
//Construction date: 2008.12.12
//*******************************************************************
void WriteDs1302(unsigned char addr, unsigned char code)
 {
     RST = 0; //It can be cleared
     CLK = 0; //Clock clears
     RST = 1; //Use valid
      
     WriteByte(addr & 0xfe); //Write address
     WriteByte(code); //Write data
   
     CLK = 1; //Clock sets
     RST = 0; //It can be invalid
 } 
//***********************************************************************
//Function name: ReadDs1302(addr);
//Input parameter: register address
//Output parameter: function data
//Function description: Ds1302 read operation
//Build date: 2008.12.12
//*******************************************************************
unsigned char ReadDs1302(unsigned addr)
 {   
     unsigned char code;

     RST = 0; //Clear
     CLK = 0; //Clear clock
     RST = 1; //Use valid
      
     WriteByte(addr | 0x01); //Write address
     code = ReadByte(); //Read data
   
     CLK = 1; //Set clock
     RST = 0; //Fail

     return code; //Return data
 }

//*******************************************************************
//Function name: TimeCahr();
//Input parameter: None
//Output parameter: None
//Function description: Clock conversion character
//Construction date: 2008.12.12
//*******************************************************************
void TimeCahr(void)
 {     
     unsigned char data;
     
     data = ReadDs1302(0x8c); //Year data
     TopChar[2] = 0x30 + (data >> 4); //Year tens digit
     TopChar[3] = 0x30 + (data & 0x0f); //Year ones digit

     data = ReadDs1302(0x88); //Month data
     TopChar[5] = 0x30 + (data >> 4); //Month tens digit
     TopChar[6] = 0x30 + (data & 0x0f); //Month units digit
 
     data = ReadDs1302(0x86); //Day data
     TopChar[8] = 0x30 + (data >> 4); //Day tens digit
     TopChar[9] = 0x30 + (data & 0x0f); //Day units digit
     
     data = ReadDs1302(0x84); //Clock data
     BotChar[0] = 0x30 + (data >> 4); //Hour tens digit  
     BotChar[1] = 0x30 + (data & 0x0f); //Hour units digit
       
     data = ReadDs1302(0x82); //Minutes data
     BotChar[3] = 0x30 + (data >> 4); //Minutes Tens digit  
     BotChar[4] = 0x30 + (data & 0x0f); //Minutes Units
       
     digit data = ReadDs1302(0x80); //Seconds data
     BotChar[6] = 0x30 + (data >> 4); //Seconds Tens digit  
     BotChar[7] = 0x30 + (data & 0x0f); //Seconds Units digit 
 }

//***********************************************************************
//Function name: Picture();
//Input parameters: None
//Output parameters: None
//Function description: Display picture
//Construction date: 2008.12.12
//*******************************************************************
void Picture(void)
 {
     TopChar[0] = '2'; //Default year
     TopChar[1] = '0';
     TopChar[4] = '/'; //Date label
     TopChar[7] = '/';
     BotChar[2] = ':'; //Clock label
     BotChar[5] = ':';
 }

//*******************************************************************
//Function name: Ds1302Init();
//Input parameter: None
//Output parameter: None
//Function description: Clock chip setting
//Build date: 2008.12.12
//*******************************************************************
void Ds1302Init(void)
 {
     unsigned char code;    
    
     code = ReadDs1302(0x80); //Read oscillator

     if (code & 0x80) //Whether to stop vibration
     {
       WriteDs1302(0x8e, 0x00); //Allow writing
       WriteDs1302(0x8c, 0x08); //Default date
       WriteDs1302(0x88, 0x01);
       WriteDs1302(0x86, 0x01);
       WriteDs1302(0x84, 0x00); //Default time    
       WriteDs1302(0x82, 0x00);                           
       WriteDs1302(0x80, 0x00);
       WriteDs1302(0x8e, 0x80); //Prohibit writing
     } 
     
     code = ReadDs1302(0x90); //Charging status
      
     if (code != 0xab) //Settings do not match 
     {
       WriteDs1302(0x8e, 0x00); //Allow
       writingWriteDs1302(0x90, 0xab); //Charging                                  
       settingWriteDs1302(0x8e, 0x80); //Prohibit writing
     }
 }

//***********************************************************************
//Function name: main();
//Input parameters: None
//Output parameters: None
//Function description: Main program
//Construction date: 2008.12.12
//*******************************************************************
void main(void)                                            
 {   
     unsigned char count, i;
 
     PortInit(); //Pin setting                   
     LcdInit(); //LCD setting
     Ds1302Init(); //Clock setting 
     TimeCahr(); //Time conversion
     Picture(); //Display label
 
     while (1)
     {
       AddrSite(0, 0); //Coordinate setting
       PrintChar(TopChar, 16); //Send character
       
       AddrSite(0, 1); //Coordinate setting
       PrintChar(BotChar, 16); //Send character

       DelayMs(100); //Update cycle
       TimeCahr(); //Update time
     }  
 }