[Blue Bridge Road -- bug free code] analysis of AT24C02 storage code

subject ： Store boot times in AT24C02 in , Range 0~100, And displayed by nixie tube

main.c

#include"STC15F2K60S2.h"
#include"iic.h"
#include"intrins.h"

typedef unsigned char uchar;
typedef unsigned int uint;

uchar dsp_code[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};
uchar dsp_Val[8]={0xff,0xff,0xff,0xff,0xff,0xff};
uchar value;

void Delay300ms()		//@11.0592MHz
{
	unsigned char i, j, k;

	_nop_();
	_nop_();
	i = 13;
	j = 156;
	k = 83;
	do
	{
		do
		{
			while (--k);
		} while (--j);
	} while (--i);
}

void Timer0Init(void)		//1 millisecond @11.0592MHz
{
	AUXR |= 0x80;		// Timer clock 1T Pattern 
	TMOD &= 0xF0;		// Set timer mode 
	TL0 = 0xCD;		// Set initial value of timing 
	TH0 = 0xD4;		// Set initial value of timing 
	TF0 = 0;		// eliminate TF0 sign 
	TR0 = 1;		// Timer 0 Start timing 
	ET0=1;
	EA=1;
}

void serviceTimer() interrupt 1
{
	static uchar dsp_com=0;

	P0=0;P2=0xc0;P2=0;

	P0=dsp_Val[dsp_com];P2=0xe0;P2=0;

	P0=1<<dsp_com;P2=0xc0;P2=0;

	if(++dsp_com==8)dsp_com=0;
}

void Initsystem()
{
	P0=0xff;P2=0x80;P2=0;
	P0=0x00;P2=0xa0;P2=0;
}

void main()
{
	Initsystem();
	Delay300ms();
	value=read_24c02(0x00);
	if(value>99)
	{
		value=0;
	}
	write_24c02(0x00,++value);
	Timer0Init();
	while(1)
	{
		if(value>9)
		dsp_Val[6]=dsp_code[value/10];
		else
		dsp_Val[6]=0xff;
		dsp_Val[7]=dsp_code[value%10];
	}
}

iic.c

/*
   Program description : IIC Bus driver 
   Software environment : Keil uVision 4.10 
   Hardware environment : CT107 SCM comprehensive training platform  8051,12MHz
   Japan      period : 2011-8-9
*/

#include "reg52.h"
#include "intrins.h"
#define DELAY_TIME 5  


#define SlaveAddrW 0xA0
#define SlaveAddrR 0xA1

// Bus pin definition 
sbit SDA = P2^1;  /*  cable  */
sbit SCL = P2^0;  /*  Clock line  */

void IIC_Delay(unsigned char i)
{
	do
	{
		_nop_();
	}
	while(i--);
}

// Bus start condition 
void IIC_Start(void)
{
	SDA = 1;
	SCL = 1;
	IIC_Delay(DELAY_TIME);
	SDA = 0;
	IIC_Delay(DELAY_TIME);
	SCL = 0;	
}

// Bus stop condition 
void IIC_Stop(void)
{
	SDA = 0;
	SCL = 1;
	IIC_Delay(DELAY_TIME);
	SDA = 1;
	IIC_Delay(DELAY_TIME);
}



// Waiting for an answer 
bit IIC_WaitAck(void)
{
	bit ackbit;
	SCL=1;
	IIC_Delay(DELAY_TIME);
	ackbit=SDA;
	SCL=0;
	IIC_Delay(DELAY_TIME);

	return ackbit;
	
}

// adopt I2C The bus sends data 
void IIC_SendByte(unsigned char byt)
{
	unsigned char i;
	for(i=0;i<8;i++)
	{   
		SCL=0;
		IIC_Delay(DELAY_TIME);
		if(byt&0x80) 
		{	
			SDA = 1;
		}
		else 
		{
			SDA = 0;
		}
		IIC_Delay(DELAY_TIME);
		SCL = 1;
		byt <<= 1;
		IIC_Delay(DELAY_TIME);	
	}
	SCL = 0;
	IIC_WaitAck();
}

// from I2C Data is received on the bus 
unsigned char IIC_RecByte(void)
{
	unsigned char da;
	unsigned char i;
	
	for(i=0;i<8;i++)
	{   
		SCL = 1;
		IIC_Delay(DELAY_TIME);
		da <<= 1;
		if(SDA) 
		da |= 0x01;
		SCL = 0;
		IIC_Delay(DELAY_TIME);
	}
	IIC_WaitAck();
	return da;
}

void IIC_SendAck(bit ackbit)
{
	SCL=0;
	SDA=ackbit;
	IIC_Delay(DELAY_TIME);
	SCL=1;
	IIC_Delay(DELAY_TIME);
	SCL=0;
	IIC_Delay(DELAY_TIME);
	SDA=1;
	IIC_Delay(DELAY_TIME);
}

unsigned char read_24c02(unsigned char add)
{
	unsigned char val;

	IIC_Start();
	IIC_SendByte(0x90);
	IIC_SendByte(add);

	IIC_Start();
	IIC_SendByte(0x91);
	val=IIC_RecByte();
	IIC_Stop();

	return val;
}

void write_24c02(unsigned char add,unsigned char dat)
{
	IIC_Start();
	IIC_SendByte(0xa0);
	IIC_SendByte(add);
	
	IIC_SendByte(dat);
	IIC_Stop();
}	

iic.h

#ifndef _IIC_H
#define _IIC_H

// Function declaration 
void IIC_Start(void); 
void IIC_Stop(void);  
void IIC_SendAck(bit ackbit); 
void IIC_SendByte(unsigned char byt); 
bit IIC_WaitAck(void);  
unsigned char IIC_RecByte(void); 
unsigned char read_24c02(unsigned char add);
write_24c02(unsigned char add,unsigned char dat);

#endif