Issue while calculating the CRC for logical address block in Flash

[sudheerrajulapu]

Hi all,

I came accross with an issue , while i am calculating the CRC for particular location in Flash memory.

In File1.c(for reference), i am passing start and end address of the block to fucntion where calculating the CRC.

But, while Debuging  i noticed that, CRC calculating for 8000 to FFFF instead of 7EC000 to 7EFFFF.

and while returning the value it's returning 2 byte value instead of 4 byte value.

but variable crc holding the 4 bytes values

IDE: CW

Microcontroller: MC9S12XS128

file1.c

#define BLOCK1START      0xFB8000

#define BLOCK1END        0xFBBFFF

crcBoot[0]= _Checksum_CheckAreaCRC32_PreCalc(BLOCK1START,((BLOCK1END+0x1)-BLOCK1START));

file2.c

_CheckSum4ByteType _Checksum_CheckAreaCRC32_PreCalc(_CHECKSUM_ConstMemBytePtr start, unsigned int len) {

  const _CheckSum1ByteType*_CHECKSUM_QUALI ptr= (const _CheckSum1ByteType* _CHECKSUM_QUALI)start;

  _CheckSum4ByteType crc = 0xFFFFFFFF;

  const _CheckSum1ByteType* _CHECKSUM_QUALI endPtr= ptr + len;

  while (ptr != endPtr) {

      crc= CheckSumByteCRC32_PreCalc(crc, *ptr);

    //__FEED_COP;     /* COP enabled? If so, feed it */

    PTM=PTM^0x04;     /* toggle self reset */

    ptr++;  

  }

    return (crc); /*== check->checkSumCRC32 *

please help me on above issue, how to pass address properly and how to return values correctly without losing 2 bytes value...

thanks in advance

[RadekS]

You have to use far pointers.

In attachment you can find simple example code for CRC calculation.

Note: I created this example code for S12G. In case of S12XS we can use global addresses (default for far pointers in case of S12X) and calculate checksum in one loop.

Note: More details about checksum calculation and automatic checksum calculation by CW you can find in example codes on your disk. Example path is:

"C:\Program Files\Freescale\CWS12v5.1\(CodeWarrior_Examples)\HC12\Checksums\2. Single App"