crc16.c

8051F_Modbus.rar是在C8051F020单片机上编写的ＣＲＣ１６校验的MODBUS协议.

//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------

#include <c8051f020.h>                 // SFR declarations
#include <stdio.h>
#include <string.h>
#include <intrins.h>
//-----------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F02x
//-----------------------------------------------------------------------------

sfr16 DP       = 0x82;                 // data pointer
sfr16 TMR3RL   = 0x92;                 // Timer3 reload value
sfr16 TMR3     = 0x94;                 // Timer3 counter
sfr16 ADC0     = 0xbe;                 // ADC0 data
sfr16 ADC0GT   = 0xc4;                 // ADC0 greater than window
sfr16 ADC0LT   = 0xc6;                 // ADC0 less than window
sfr16 RCAP2    = 0xca;                 // Timer2 capture/reload
sfr16 T2       = 0xcc;                 // Timer2
sfr16 RCAP4    = 0xe4;                 // Timer4 capture/reload
sfr16 T4       = 0xf4;                 // Timer4
sfr16 DAC0     = 0xd2;                 // DAC0 data
sfr16 DAC1     = 0xd5;                 // DAC1 data
unsigned int  crc;
unsigned char  test[6]={0x01,0x03,0x00,0x00,0x00,0x02};
unsigned char *pp;
unsigned char temp,temp2;
  

unsigned int crc16(unsigned int num);
void SYSCLK_Init (void);

void main(void)
{
  
   WDTCN = 0xde;                       // disable watchdog timer
   WDTCN = 0xad;
   SYSCLK_Init ();
   crc=crc16(0x0006);
  while(1);
  
  
}

unsigned int crc16(unsigned int num)
{
   int i,j;
   unsigned int c,crc=0xFFFF;
   for (i=0;i<num;i++)
   {
       c=test[i] & 0x00FF;
       crc^=c;
	  for(j=0;j<8;j++)
	  { 
	      if (crc & 0x0001)
		  {
		     crc>>=1;
			 crc^=0xA001;
		   }
		   else 
		   {
		     crc>>=1;
           }
       }
     }
   return(crc);
}


void SYSCLK_Init (void)
{
   int i;                              // delay counter

   OSCXCN = 0x67;                      // start external oscillator with
                                       // 22.1184MHz crystal

   for (i=0; i < 256; i++) ;           // wait for crystal osc. to start up

   while (!(OSCXCN & 0x80)) ;          // Wait for crystal osc. to settle

   OSCICN = 0x88;                      // select external oscillator as SYSCLK
                                       // source and enable missing clock
                                       // detector
}