pointers

  if(RI == 1)  /* Receiver Interrupt Flag -- SBUF has the character  */
  {
    RI = 0 ;   /* Clear the Receive Interrupt Flag                   */
    SDE = 0 ;  /* Clear the Error Flag                               */
    if(sp_nRx < SP_RX_SIZE)  /* Check to see if there is room        */
    {
      if(FE == 1)  /* Check for Framing Errors                       */
      {							
        FE = 0 ;  /* Clear the framing error bit                     */
        ++g_RxFramingError ;
        ACC = SBUF ;  /* Check for BREAK                             */
        if(ACC == 0)	BREAK = 1 ;
      }
      else
      {
        sp_RxBuffer[sp_RxPut] = SBUF ;
        sp_RxPut = (sp_RxPut + 1) & (SP_RX_SIZE - 1) ;
        ++sp_nRx ;
      }
    }
    else  /* One space remains	*/
    {
      if(FE == 1)
      {
        FE = 0 ;  /* Clear the framing error bit  */
        ++g_RxFramingError ;
        ACC = SBUF ;  /* Check for BREAK  */
        if(ACC == 0)	BREAK = 1 ;
      }
      else
      {	/* Continue to overwrite the last character
        ** Don't increment the pointer
        ** Don't increment the count of characters in the queue
        */
        sp_RxBuffer[sp_RxPut] = SBUF ;
        ++g_RxDataOverrun ;
        LSDE = SDE = 1 ;
      }
    }
  }