//Interrupt Programming with CodeWarrior on Dragon12+ Using SCI0 Interrupt.
//Souding Buzzer of PTT5 continuously while waiting for Interrupt to come in from SCI0
//Pressing any key on x86 PC HyperTerminal/Tera Terminal will interrupt the Dragon12 
//and Dragon12 gets the character and displays it on LEDs of PORTB
//Modified by Mazidi from Example 11-12C of Chapter 11 of HCS12 textbook by Mazidi & Causey

//Serial SCI0 is the USB port next to the LCD.
//Serial SCI0 is connected to USB and used by the Serial Monitor to communicate (downLOAD and RUN) with the Trainer board 
                                           
//This program must be downloaded into Dragon12 via USB/COM0 using HCS12 Serial Monitor
//Use the usual steps in CodeWarrior. a) Make (F7) b) Set SW7 =00 (LOAD) position, c)use Debug (F5) to download.  
//After it is downloaded, d)close the Debugger Windows of CodeWarrior from step C, and e) set SW7=10 (RUN) position
//(f) bring up HyperTerminal (or Tera Term in Windows Vista and Windows 7), 
//and g) MAKE SURE TO press RESET on the Dragon12 board and it will run this program. 
//(h) to download another program, close the HyperTerminal and set SW7=00 for LOAD.   

//Serial Monitor uses USB(SCI0) to download (LOAD,SW7=00) and works at 48 MHz
//The RUN mode (SW7=10) of Dragon12+ works at 8 MHz Use this for 9600 baud rate caculation..
//We use USB(SCI0) to download using Serial Monitor 
//and then switch to RUN to send data to HyperTerminal/Tara Terminal using the same SCI0 


//Make sure to choose "minimal startup code" and "Small" for memory model(no banked) when creating porject for Interrupts 
//Close and open HyperTerminal/TeraTerminal everytime you run this program 

//To Run this program Make sure to press RESET on Dragon12 board after the download and making SW7=10 for RUN. 

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

void MSDelay(unsigned int);
void main(void) 
{
  DDRB = 0xFF;      //PTB as output for LEDs
  DDRJ = 0xFF;      //PTJ as output
  DDRT = 0xFF;      //PORTT as output for PT5 buzzer
  PTJ = 0x0;        //Let PTB show data. Needed by Dragon12+ board
  SCI0BDH=0x00;    //Serial Monitor used for LOAD works at 48MHz  

  SCI0BDL=26;      //8MHz/2=4MHz, 4MHz/16=250,000 and 250,000/9600=26 for run when SW=10 
  SCI0CR1=0x00;
  SCI0CR2=0x2C;    //enable receive interrupt too
  
  
    __asm CLI;  //Enable interrupts globally				
  
  for(;;) 
  {                                //do something
  
  PTT = PTT ^ 0x20;      //sound the buzzer by toggling PT5

  MSDelay(10);
  
  } //stay here until interrupt comes.
}

   
//SCI0 Interrupt, Pressing any key on HyperTerminal/TeraTerminal will send a charater to Dragon12 via SCI0 port
//and Dragon12 gets the character and displays it on LEDs of PORTB    

interrupt (((0x10000-Vsci0)/2)-1) void SCI0_ISR(void)
  {
   if(SCI0SR1 & SCI0SR1_RDRF_MASK)	
     PORTB=SCI0DRL;
   
  
  }   
  
 void MSDelay(unsigned int itime)
  {
    unsigned int i; unsigned int j;
    for(i=0;i<itime;i++)
      for(j=0;j<4000;j++);
  }