BYTE SD_Init()
{
   WORD CardStatus; // R2 value from status inquiry...
   WORD Count;      // local counter
   
   // Global CardType - b0:MMC, b1:SDv1, b2:SDv2

   /* initial speed is slow... */
   SPI_Init( kHz400 );
   
   /* disable SPI chip select... */
   SPI_DisableCS();

   /* fill send data with all ones - 80 bits long to   */
   /* establish link with SD card this fulfills the    */
   /* 74 clock cycle requirement...  */
   for(Count=0;Count<10;Count++)
      SPI_Byte( 0xFF );

   /* enable the card with the CS pin... */
   SPI_EnableCS();

   /* ************************************************ */
   /* SET SD CARD TO SPI MODE - IDLE STATE...          */
   /* ************************************************ */
   Count = 1000;     // one second...
   CardType = 0;
   
   /* wait for card to enter IDLE state... */
   do
   {
      Delay(1);
      SD_Command( CMD_GO_IDLE_STATE, 0 );
   } while((SD_GetR1() != IDLE_STATE) && (--Count));  

   /* timeout if we never made it to IDLE state... */
   if( !Count )
      return( SD_TIME_OUT );

   /* ************************************************ */
   /* COMPLETE SD CARD INITIALIZATION                  */
   /* FIGURE OUT WHAT TYPE OF CARD IS INSTALLED...     */
   /* ************************************************ */
   Count = 2000;     // two seconds...
   
   /* Is card SDSC or MMC? */
   SD_Command( CMD_APP_CMD, 0 );
   SD_Command( ACMD_SEND_OP_COND, 0 );
   if( SD_GetR1() <= 1 )
   {
      CardType = 2;
   }
   else
   {
      CardType = 1;
   }
   
   /* wait for initialization to finish... */
   do
   {
      Delay(1);
      if( CardType == 2 )
      {
         SD_Command( CMD_APP_CMD, 0 );
         SD_Command( ACMD_SEND_OP_COND, 0 );
      }
      else
      {
         SD_Command( CMD_SEND_OP_COND, 0 );
      }
   } while(SD_GetR1() && --Count);

   if( !Count )
      return( SD_TIME_OUT );

   /* ************************************************ */
   /* QUERY CARD STATUS...                             */
   /* ************************************************ */
   SD_Command( CMD_SEND_STATUS, 0 );
   CardStatus = SD_GetR2();

   if( CardStatus )
      return( SD_ERROR );

   /* ************************************************ */
   /* SET BLOCK SIZE...                                */
   /* ************************************************ */
   SD_Command( CMD_SET_BLOCKLEN, 512 );
   if( SD_GetR1() )
   {
      CardType = 0;
      return( SD_ERROR );
   }

   /* ************************************************ */
   /* SWITCH TO HIGHEST SPI SPEED...                   */
   /* ************************************************ */
   SPI_Init( MHz10 );

   /* disable the card with the CS pin... */
   SPI_DisableCS();

   /* return OK... */
   return( 0 );
}