//Interrupt programming with CodeWarrior on Dragon12+ with Real Time Interrupt (RTI) 
//Buzzer sounds continuously while waiting for AN Interrupt
//PORTB.4 Toggle every Second using RTI (real time interrupt) 
//Modified from example 11-18C of HCS12 textbook by Mazidi & Causey.

//Remember RTI uses the XTAL freq. (not the bus Freq) which is XTAL=8 MHz on Dragon12+ board 
 
//Make sure to choose "minimal startup code" and "Small" for memory model(no banked) when creating porject for Interrupts  

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

void MSDelay(unsigned int);
unsigned int COUNT;
void main(void) 
{
  DDRB = 0xFF;   //PORTB =output for LEDs
  DDRJ=0xFF;     //PTJ = output    for LEDs
  DDRT = 0xFF;   //PTT = output for Buzzer
  PTJ = 0x0;    //Needed by Dragon12+ board
  
 
 //Real time Interrupt (RTI) setup 
  CRGINT = CRGINT | CRGINT_RTIE_MASK;     //enable RTI 	
  RTICTL = 0b01111111;	//(longest RTI is about 0.13 sec) Change this number to see toggling rate for RTI	
  COUNT = 0;				
   
 
    __asm CLI;  	//Enable interrupts globally			
  
  for(;;)    //  Sound the Buzzer at PTT5 forever and wait for interrupt
  {                            //do something
  PTT = PTT ^ 0b00100000;     //sound the buzzer continuously 
  MSDelay(100);
  
  } //stay here in this loop until an interrupt comes in.
}

//------ Real Time Interrupt ISR (Toggling the PORTB4 every Sec.)
interrupt (((0x10000-Vrti)/2)-1) void RTI_ISR(void)
{
  COUNT++;					
  if(COUNT==8) 	//8 x 0.13 sec = 1 sec	also change this number for shorter or longer durations
  {
    PORTB = PORTB ^ PORTB_BIT4_MASK; 	//Toggle PORTB.4
    COUNT = 0;      			
  }
  CRGFLG = CRGFLG | CRGFLG_RTIF_MASK; //clear it for next round	
}
//-------end of ISR   
  
 void MSDelay(unsigned int itime)
  {
    unsigned int i; unsigned int j;
    for(i=0;i<itime;i++)
      for(j=0;j<4000;j++);
  }