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CAN-Routines generated by Dave

Joachim Leonhard

Infineons Dave generates the following code for FIFO-Reception of CAN-Messages:

// @Controller    Infineon XC167CI-16F40
//
// @Compiler      Keil
//
// @Codegenerator 2.4

ubyte CAN_ubReadFIFO(ubyte ubObjNr, TCAN_SWObj *pstObj)
{
  ubyte i,j;
  ubyte ubReturn;

  ubReturn = 2;

  if((CAN_HWOBJ[ubObjNr].uwCANPTR & 0x0700) == 0x0200)  // if FIFO base object
  {
    j = aubFIFOReadPtr[ubObjNr / 2];

    ubReturn = 0;
    if((CAN_HWOBJ[j].uwMSGCTR & 0x0300) == 0x0200)    // if NEWDAT
    {
      CAN_HWOBJ[j].uwMSGCTR = 0xfdff;                 // clear NEWDAT

      // CANPTRn(new) = CANPTR(old) & ~(uword)FSIZEn | (CANPTRn(old) + 1) & FZIZEn
      aubFIFOReadPtr[ubObjNr / 2] = ((aubFIFOReadPtr[ubObjNr / 2] & ~(uword)(CAN_HWOBJ[ubObjNr].uwCANFCR & 0x001f)) |
                                    ((aubFIFOReadPtr[ubObjNr / 2] + 1) & (CAN_HWOBJ[ubObjNr].uwCANFCR & 0x001f)));

      // check if the previous message was lost
      if((CAN_HWOBJ[j].uwMSGCTR & 0x0c00) == 0x0800)  // if set MSGLST
      {
        CAN_HWOBJ[j].uwMSGCTR = 0xf7ff;               // reset MSGLST
        return(3);
      }

      for(i = 0; i < (CAN_HWOBJ[j].uwMSGCFG & 0x00f0) >> 4; i++)
      {
        pstObj->ubData[i] = CAN_HWOBJ[j].ubData[i];
      }

      if(CAN_HWOBJ[j].uwMSGCFG & 0x04)        // if extended identifier
      {
        pstObj->ulID   = CAN_HWOBJ[j].ulCANAR;
      }
      else                                    // if standard identifier
      {
        pstObj->ulID   = CAN_HWOBJ[j].ulCANAR >> 18;
      }

      pstObj->uwMsgCfg  = CAN_HWOBJ[j].uwMSGCFG;

      // check if the message was corrupted
      if((CAN_HWOBJ[j].uwMSGCTR & 0x0300) == 0x0200)  // if NEWDAT
      {
        CAN_HWOBJ[j].uwMSGCTR = 0xfdff;               // clear NEWDAT
        return(4);
      }
      ubReturn = 1;
    }
  }
  return(ubReturn);

} //  End of function CAN_ubReadFIFO

It seems to me that there is at least one bug: In the Line

      CAN_HWOBJ[j].uwMSGCTR = 0xfdff;                 // clear NEWDAT


the complete register is set with a constant instead of only resetting the newdat-bits. Two lines later this register is checked for the MSGLost-Bits, which will never be true:

      if((CAN_HWOBJ[j].uwMSGCTR & 0x0c00) == 0x0800)  // if set MSGLST


Does anybody have an idea, what happens here?

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