//Interrupt Programming with CodeWarrior on Project Board with HCS12 MCU Module Using PTP Interrupt.
//An LED on PORTA toggles continuously while waiting for Interrupt to come in from push Button Switches on PB1 or PB2
//Pressing any of PB1 or PB2 Push Button switches will interrupt the main and sound the buzzer for a short period of time.

//before you run this program, run the Push Button PB1-PB2 program on this website to establish the fact that the PB1 and PB2 work.

//See Chapter 11 of HCS12 textbook by Mazidi & Causey
 


//The lower 4 bits of PA3-PA0 (pins of HCS12 CPU) are connected to LEDs(LED1-LED4 on J10) permanently
//and must be enabled by clearing bit P4 of PORTP. Also set the LED jumper on UFEA jumpers next to Buzzer
//We also need to connect 4 wires from LED5-LED8 (J10) to pins PA7-PA4 via J6 connector 

//The lower 2 bits of PP1-PP0 (pins of HCS12 CPU) are connected to Push Buttons of PB1 and PB2 permanently
//and must be enabled by clearing bit P5 of PORTP. Also set the PB jumper on UFEA jumpers next to Buzzer



//On HCS12 MCU Module itself 
//a)MAKE SURE BOTH jumpers for PP0 and PP1 are removed (SW1 and SW2).
//b)Also Make sure 8 Jumpers (SW3-1 to SW3-4 and LED1-LED4) on HCS12 MCU module are also removed  
            

          
//Written and tested by M. Mazidi using Examples in chap. 7 of HCS12 textbook by Mazidi & Causey.

//Make sure to choose "minimal startup code" and "Small" for memory model(no banked) when creating porject for Interrupts  
//In CodeWarrior,MAKE sure you are in TBDML Mode before downloading 
//Press F7 (to Make), then F5(Debug) to downLOAD,and F5 once more to start the program execution

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


void MSDelay(unsigned int);
void main(void) 
{
  /* put your own code here */
  

    DDRA = 0xFF;    //PORTA as output since LEDs are connected to it
    DDRP = DDRP | 0b00110000;  //PP4 and PP5 as output. On the Project Board, a)the lower 4 pins of PA3-PA0 are connected to LEDs(LED1-LED4) 
    PTP = PTP & 0b11001111;    //and b)the PP0 and PP1 pins are connected to PB1 and PB2 push buttons. c) They mut be enabled by clearing pins P4 and P5 of PORTP
                 //on Project Board,we need to connect 4 wires from LED5-LED8 (J10) to pins PA4-PA7 via J6 connector (pins 25,27,29,31)
   
    DDRT = DDRT | 0b00000001;    // PTT0 as output for Buzzzer on Project Board
        
    
  PIEP = 0xFF;   //enable PTP interrupt
  PPSP = 0xFF;   //Make it rising Edge-Trig (change to 0 to see the falling-edge.
  
    __asm CLI;  //Enable interrupts globally				
  
  for(;;) 
  {                                //do something
  PORTA = PORTA ^ 0b00000001;     //Toggle PORTA0 while waiting for Interrupt
  MSDelay(100);
  
  } //stay here until interrupt come.
}

   
//PTP Interrupt, Moving any of Push Button Switches of PB1 and PB2 will sound the buzzer for short period of time   

interrupt (((0x10000-Vportp)/2)-1) void PORTP_ISR(void)
  {
    unsigned char x;
    for (x=0;x<100;x++)     //Upon PTP Interrupt (any of push Button PB1 and PB2 switch going from H-to-L) will sound the buzzer for a short period 			
      {
       PTT = PTT ^ 0b00000001;       //toggle PT0 for Buzzer
      MSDelay(10);		    //how long the Buzzer should sound. During the buzzer sound PORTA0 stops toggling. Why? 		
        
      }
 

  PIFP = PIFP | 0xFF;      //clear PTP Interupt Flags for the next round. Writing HIGH will clear the Interrupt flags
  }   
  
 void MSDelay(unsigned int itime)
  {
    unsigned int i; unsigned int j;
    for(i=0;i<itime;i++)
      for(j=0;j<325;j++);
  }