eeprom容量分成2份，一份作为常用区，一份作为备份区。

参数保存函数，先写入常用区，再写入备份区。

参数读取函数，先读常用区，成功则退出，不成功则读取备份区，成功则刷新常用区。

系统有多个参数，各个参数分开保存。这种方式的好处是方便扩展，新增参数不会影响到旧参数，缺点是开机加载参数时读取参数的次数多。

#define AT24C256

#ifdef AT24C256
	#define EE_MODEL_NAME		"AT24C256"
	#define EE_DEV_ADDR			0xA0		/* 设备地址 */
	#define EE_PAGE_SIZE		64			/* 页面大小(字节) */
	#define EE_SIZE				(32*1024)	/* 总容量(字节) */
	#define EE_ADDR_BYTES		2			/* 地址字节个数 */
    #define EEP_ADDR_BACKUP_BASE		(16*1024)			/* 备份区起始地址 */
#endif

#define EEPROM_OP_TIME          3

int EEP_Save_Data( uint16_t addr, uint8_t* pdata, uint32_t len )
{
    uint16_t            l_u16WrCRC = 0;
    uint16_t            l_u16DataAddr   = addr;
    uint8_t             l_u8aWrBuff[1024];
    uint8_t             ret,ret1;
    uint8_t             errcnt;

    if(l_u16DataAddr > EE_SIZE) return -1;

    memset(l_u8aWrBuff,0x00,sizeof(l_u8aWrBuff));
    memcpy(l_u8aWrBuff,pdata,len);
    l_u16WrCRC = GetCRC16(l_u8aWrBuff,len);
    l_u8aWrBuff[ len  ] = l_u16WrCRC & 0xff;
    l_u8aWrBuff[ len + 1 ] = l_u16WrCRC >> 8;

    errcnt = 0;
    do
    {
        ret = WriteMultiByteToEEPROM( l_u8aWrBuff, l_u16DataAddr, len+2 );
    }
    while ( ret && ( ++errcnt < EEPROM_OP_TIME ) );

    errcnt = 0;
    do
    {
        ret1 = WriteMultiByteToEEPROM( l_u8aWrBuff, l_u16DataAddr + EEP_ADDR_BACKUP_BASE, len+2 );
    }
    while ( ret1 && ( ++errcnt < EEPROM_OP_TIME ) );

    if( ret != 0 && ret1 != 0 )
    {
        return -2;
    }
    else
    {
        return 0;
    }
}


int EEP_Read_Data( uint16_t addr, uint8_t* pdata, uint32_t len )
{
    uint16_t            l_u16Result = SUCCESS;
    uint16_t            calCRC = 0;
    uint16_t            l_u16RdCRC = 0;
    uint16_t            l_u16DataAddr   = addr;
    uint8_t             l_u8aRdBuff[1024];
    uint8_t             ret,ret1;
    uint8_t             errcnt;
    uint8_t             flag;

    if(l_u16DataAddr > EE_SIZE) return -1;

    memset(l_u8aRdBuff,0x00,sizeof(l_u8aRdBuff));
    errcnt = 0;
    do
    {
        ret = ReadMultiByteFromEEPROM( l_u8aRdBuff, l_u16DataAddr, len+2 );
    }
    while ( ret && ( ++errcnt < EEPROM_OP_TIME ) );

    if( ret == 0 )
    {
        memcpy(pdata,l_u8aRdBuff,len);
        return 0;
    }
    else
    {
        errcnt = 0;
        do
        {
            ret1 = ReadMultiByteFromEEPROM( l_u8aRdBuff, l_u16DataAddr + EEP_ADDR_BACKUP_BASE, len+2 );
        }
        while ( ret1 && ( ++errcnt < EEPROM_OP_TIME ) );
        if(ret1 == 0) 
        {
            memcpy(pdata,l_u8aRdBuff,len);
            errcnt = 0;
            do
            {
                ret = WriteMultiByteToEEPROM( l_u8aRdBuff, l_u16DataAddr, len+2 );
            }
            while ( ret && ( ++errcnt < EEPROM_OP_TIME ) );
            return 0;
        }    
        else
            return -1;
    }

}