Interfacing MCP2317 with atmega8

#include "SPI.h"
//sbit Chip_Select at PORTB0_bit;
//sbit Chip_Select_Direction at DDB0_bit;
#define reset    PORTB.f1
#define CS       PORTB.f0
//-------------------------------------------------------------------------------------------------
// porta A
unsigned char const MCP2317_IODIRA   = 0x00;   // direction
unsigned char const MCP2317_IPOLA    = 0x02;   // polarity  of gpio- setting one inverts
unsigned char const MCP2317_GPINTENA = 0x04;   // interrupt
unsigned char const MCP2317_DEFVALA  = 0x06;   // default value change for Interrupt to occur
unsigned char const MCP2317_INTCONA  = 0x08;   //interrupt on changae
unsigned char const MCP2317_IOCONA   = 0x0A;   // configuration register
unsigned char const MCP2317_GPPUA    = 0x0C;   // pull up enable or disable
unsigned char const MCP2317_INTFA    = 0x0E;   // Interrupt flag register
unsigned char const MCP2317_INTCAPA  = 0x10;   ///interrupt capture register
unsigned char const MCP2317_GPIOA    = 0x12;   // PIN state register
unsigned char const MCP2317_OLATA    = 0x14;   // reading pin values

//   porta B
unsigned char const MCP2317_IODIRB   =0x01;
unsigned char const MCP2317_IPOLB    =0x03;
unsigned char const MCP2317_GPINTENB =0x05;
unsigned char const MCP2317_DEFVALB  =0x07;
unsigned char const MCP2317_INTCONB  =0x09;
unsigned char const MCP2317_IOCONB   =0x0B;
unsigned char const MCP2317_GPPUB    =0x0D;
unsigned char const MCP2317_INTFB    =0x0F;
unsigned char const MCP2317_INTCAPB  =0x11;
unsigned char const MCP2317_GPIOB    =0x13;
unsigned char const MCP2317_OLATB    =0x15;

unsigned char const MCP2317_OPCODE_WRITE =0x40;
unsigned char const MCP2317_OPCODE_READ  =0x41;

unsigned char letto_a=0x00   ; //absolute 0x0020;   // forces the variable to be in a particular location
unsigned char letto_b=0x00   ; //absolute 0x0021;

void MCP2317_Write(unsigned char  const opcode,unsigned char const address, unsigned char dato);
unsigned char MCP2317_Read(unsigned char const opcode, unsigned char const address);
//-------------------------------------------------------------------------------------------------
void main()
{
DDRB.B0=0;
DDRB.B1=0;
//SPI1_Init_Advanced(_SPI_MASTER_OSC_DIV64, _SPI_DATA_SAMPLE_MIDDLE,_SPI_CLK_IDLE_LOW, _SPI_LOW_2_HIGH);
SPI1_Init();
PORTB.f1=0;
delay_ms(100);
PORTB.f1=1;

//--------------- configur IOCONA-------------------//
  MCP2317_Write(MCP2317_OPCODE_WRITE,MCP2317_IOCONA,0x20);             //seq operation disabled
//----------------configuro registro  IOCONB------------------//
  MCP2317_Write(MCP2317_OPCODE_WRITE,MCP2317_IOCONB,0x20);             //seq operation disabled


//----------------configur porta B ------------//
  MCP2317_Write(MCP2317_OPCODE_WRITE,MCP2317_IODIRB,0x00);                   // direction  to output
//----------------scrivo sulla porta B 0x00-------------------//
  MCP2317_Write(MCP2317_OPCODE_WRITE,MCP2317_OLATB,0x00);                   /// ?????


//----------------configur  porta A -------------//
  MCP2317_Write(MCP2317_OPCODE_WRITE,MCP2317_IODIRA,0xFF);                   //direction  to input


while (1)
   {
    letto_b=MCP2317_Read( MCP2317_OPCODE_READ,MCP2317_GPIOA);
    letto_b = letto_b & 0x01;

    if(letto_b == 0x01)
    {
     MCP2317_Write(MCP2317_OPCODE_WRITE,MCP2317_GPIOB,0xF0); //MCP2317_OLATB    both are used - isnt clear which one has to be used
     Delay_ms(100);
      //Lcd_Out(2,17,"yes we have it");
    }
    else
    {
     MCP2317_Write(MCP2317_OPCODE_WRITE,MCP2317_GPIOB,0x0F); //MCP2317_OLATB    both are used - isnt clear which one has to be used
     Delay_ms(100);
    }
    Delay_ms(100);
   }


}



void MCP2317_Write( unsigned char const opcode,unsigned char const address,
                    unsigned char dato)
{
  PORTB.f0=0;
  SPI1_Write(opcode);
  SPI1_Write(address);
  SPI1_Write(dato);
  PORTB.f0=1;
}

unsigned char MCP2317_Read(unsigned char const opcode,
                           unsigned char const address)
{
   unsigned char letto_p;
   PORTB.f0=0;
   SPI1_Write(opcode);
   SPI1_Write(address);
   letto_p=SPI1_Read(0);
   PORTB.f0=1;
   return letto_p;
}