crc_calc_checksum.c

Mplab C30编译器

#if defined(__PIC24F__)
#include <p24Fxxxx.h>
#endif
#include "crc.h"

#ifdef _CRC_PROG_V1

#define WRITE_CRC_DATA_WORD(data)         (CRCDAT= data)
#define WRITE_CRC_DATA_BYTE(data)         (*(UINT8*)&CRCDAT = data)

#define GET_CRC_RESULT()                  (CRCWDAT)
#define SET_CRC_RESULT(data)              (CRCWDAT = data)


/***************************************************************************************
Function Prototype : UINT16 CRC_Calc_ChecksumWord(UINT16* data,UINT16 Number_of_words,
                                                    UINT16 prev_CRC)
 
Include            : crc.h
 
Description        : This function calculates CRC checksum for the data provide by the 
                     user,based on the polynomial set in the CRCXOR Register.
 
Arguments          : data - Pointer to the first data word for which CRC needs to    
                     be calculated.
                     Number_of_words - Total number of words for which CRC needs 
                     to be calculated.
                     prev_CRC - previous CRC result.
                     
Return Value       : Returns Two Byte CRC checksum based on the set polynomial.
 
Remarks            : Input parameter is provided as a provision to allow continuation 
                     of previously being computed checksum. In case the checksum is
                     being calculated for a fresh set of data then the input value for
                     prev_CRC should be '0'.
***************************************************************************************/  

UINT16 CRC_Calc_ChecksumWord(UINT16* data, UINT16 Number_of_words, UINT16 prev_CRC)
{
   SET_CRC_RESULT(prev_CRC);
   do
   {
       while(1 != Get_CRC_FIFO_EMPTY_STATUS());
       Stop_CRC_Calulation();
       while((0 == Get_CRC_FIFO_FULL_STATUS() && (0 < Number_of_words)))
       {
          WRITE_CRC_DATA_WORD(*data);
          data++;
          Number_of_words--;
       }
       Start_CRC_Calulation();
  }while (0 < Number_of_words);

   while(1 != Get_CRC_FIFO_EMPTY_STATUS());
   Nop();
   Nop();
   return(GET_CRC_RESULT());
}

/***************************************************************************************
Function Prototype : UINT16 CRC_Calc_ChecksumByte(UINT8* data, UINT16 Number_of_bytes, 
                                                  UINT16 prev_CRC)
                                                   
Include            : crc.h
 
Description        : This function calculates CRC checksum for the data provide by the 
                     user,based on the polynomial set in the CRCXOR Register.
 
Arguments          : data - Pointer to the first data byte for which CRC needs to    
                     be calculated.
                     Number_of_bytes - Total number of bytes for which CRC needs 
                     to be calculated.
                     prev_CRC - previous CRC result.
                     
Return Value       : Returns One Byte CRC checksum based on the set polynomial.
 
Remarks            : Input parameter is provided as a provision to allow continuation 
                     of previously being computed checksum. In case the checksum is
                     being calculated for a fresh set of data then the input value for
                     prev_CRC should be '0'.
*****************************************************************************************/  
UINT16 CRC_Calc_ChecksumByte(UINT8* data, UINT16 Number_of_bytes, UINT16 prev_CRC)
{
   SET_CRC_RESULT(prev_CRC);
   do
   {
       while(1 != Get_CRC_FIFO_EMPTY_STATUS());
       Stop_CRC_Calulation();
       while((0 == Get_CRC_FIFO_FULL_STATUS() && (0 < Number_of_bytes)))
       {
          WRITE_CRC_DATA_BYTE(*data);
          data++;
          Number_of_bytes--;
       }
       Start_CRC_Calulation();
   }while (0 < Number_of_bytes);

   while(1 != Get_CRC_FIFO_EMPTY_STATUS());
   Nop();
   Nop();
   return(GET_CRC_RESULT());
}

#else
#warning "Does not build on this target"
#endif