HCS12 CAN Example from NXP App note

AN3034.c

#include <hidef.h>      /* common defines and macros */
#include "derivative.h"      /* derivative-specific definitions */

#define ST_ID_100 0x100

#define ACC_CODE_ID100 0x2000
#define ACC_CODE_ID100_HIGH ((ACC_CODE_ID100 & 0xFF00)>>8)
#define ACC_CODE_ID100_LOW (ACC_CODE_ID100 & 0x00FF)

/* Mask Code Definitions */
#define MASK_CODE_ST_ID 0x0007
#define MASK_CODE_ST_ID_HIGH ((MASK_CODE_ST_ID & 0xFF00)>>8)
#define MASK_CODE_ST_ID_LOW (MASK_CODE_ST_ID & 0xFF)

void canInit()
{
  CANCTL0 = 0x01;
  while(!(CANCTL1 & 0x01));
  
  CANCTL1 = 0xA0;
  CANBTR0 = 0xC7;
  CANBTR1 = 0x3A;
  
  /* Acceptance Filters */
  CANIDAC = 0x10; /* Set four 16-bit Filters */
  CANIDAR0 = ACC_CODE_ID100_HIGH;  //|\ 16-bit Filter 0
  CANIDMR0 = MASK_CODE_ST_ID_HIGH; //| \__ Accepts Standard Data Frame Msg
  CANIDAR1 = ACC_CODE_ID100_LOW;   //| / with ID 0x100
  CANIDMR1 = MASK_CODE_ST_ID_LOW;  //|/
  /* Acceptance Filters */
  CANIDAC = 0x10; /* Set four 16-bit Filters */
  CANIDAR2 = 0x00;                 //|\ 16-bit Filter 1
  CANIDMR2 = MASK_CODE_ST_ID_HIGH; //| \__ Accepts Standard Data Frame Msg
  CANIDAR3 = 0x00;                 //| / with ID 0x100
  CANIDMR3 = MASK_CODE_ST_ID_LOW;  //|/
  CANIDAR4 = 0x00;                 //|\ 16-bit Filter 2
  CANIDMR4 = MASK_CODE_ST_ID_HIGH; //| \__ Accepts Standard Data Frame Msg
  CANIDAR5 = 0x00;                 //| / with ID 0x100
  CANIDMR5 = MASK_CODE_ST_ID_LOW;  //|/
  CANIDAR6 = 0x00;                 //|\ 16-bit Filter 3
  CANIDMR6 = MASK_CODE_ST_ID_HIGH; //| \__ Accepts Standard Data Frame Msg
  CANIDAR7 = 0x00;                 //| / with ID 0x100
  CANIDMR7 = MASK_CODE_ST_ID_LOW;  //|/
  CANCTL0 = 0x00; /* Exit Initialization Mode Request */

  while ((CANCTL1&0x00) != 0); /* Wait for Normal Mode */
}

unsigned char canSendFrame(unsigned long id, unsigned char priority, unsigned char length, unsigned char *txdata)
{
  unsigned char txbuffer;
  unsigned char index;

  if(!CANTFLG) return 1;
  
  CANTBSEL = CANTFLG;
  txbuffer = CANTBSEL;
  
  *((unsigned long *) ((unsigned long)(&CANTXIDR0))) = id;
  
  for (index=0;index<length;index++) {
    *(&CANTXDSR0 + index) = txdata[index];
  }
  CANTXDLR = length; /* Set Data Length Code */
  CANTXTBPR = priority; /* Set Priority */
  CANTFLG = txbuffer; /* Start transmission */
  while ( (CANTFLG & txbuffer) != txbuffer);
}

interrupt 38 void canRxHandler(void)
{
  unsigned char length, index;
  unsigned char rxdata[8];
  
  length = (CANRXDLR & 0x0F);
  
  for (index=0; index<length; index++)
    rxdata[index] = *(&CANRXDSR0 + index); /* Get received data */
  
  CANRFLG = 0x01; /* Clear RXF */
}

void main(void) 
{  
  unsigned char errorflag;
  unsigned char txbuff[] = "abcd";

  canInit();
  
  while (!(CANCTL0 & 0x10));
  
  CANRFLG = 0xC3;
  CANRIER = 0x01;
  
  EnableInterrupts;
  
  for (;;) 
  {
    errorflag = canSendFrame((ST_ID_100), 0x00, sizeof(txbuff)-1, txbuff);
  }
}