//Interrupt Programming with CodeWarrior on HCS12G128 Tower Using PAD (Port AD) Interrupt.
//In HCs12G128, beside the XIRQ and IRQ pins Ports P, J , and AD have harware interrupt capabilities.
//Chapter 2 of HCS12G Ref. Manual describes all the ports of HCS12G128
//Sections 2.4.3.49 through 2.4.3.64 give the details of registers associated with PAD, inclduing the interrupt registers. 

//On TWR-S12G128 Tower board, 4 LEDs (LED4-LED1)are connected to PT7-PT4 pins. PT7=LED4,.., PT4=LED1
//LED1-LED4 are active LOW.  See TWR-HCS12G128 schematic 
//The 4-pins of PAD7-PAD4 are also connected to the push-button (debounce) switches (SW1-SW4)
//SW1-SW4 are active LOW (normally HIGH) See TWR-HCS12G128 schematic 

//Make sure the jumpers for LED4-LED1 and push-button SW4-SW1 are set. 
 

//In this program, LED4 on PORTT toggles continuously while waiting for an Interrupt to come in from any push-button Switches on PAD
//Pressing any push-button switches of SW1-SW4 will interrupt the main and toggles LED7 for a short period of time.

//Written and tested based on examples in Chapter 11 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  

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

void MSDelay(unsigned int);
void main(void) 
{
    DDRT = 0b10010000;        //PT7 and PT4 as output for LED4 and LED1 
    ATDDIEN = 0x00F0;	      //Make PAD7-PAD4 as digitla Input for SW4-Sw1. (Th default PAD is analog for A-to-D)   
    PER1AD = 0xF0;	      //Enable internal pull-ups for the PAD4-PAD7 pin
    DDR1AD= DDR1AD | 0x00;     //Make PAD7-PAD4 as input. Optional since the default is input.
	  
   
  //PAD interrupt setup
  PIE1AD = 0b11110000;   //enable PAD interrupt for SW1-SW4
  PPS1AD = 0x00;        //Make it Falling Edge-Trig since SW4-Sw1 are active LOW (normally HIGH).
  
    __asm CLI;  //Enable interrupts globally
    //EnableInterrupts;  	//another way for Enabling interrupts globally				
  
  for(;;) 
  {                                //do something
  PTT = PTT ^ 0b00010000;       //Toggle LED1 continuously while waiting for Interrupt
  MSDelay(250);
  
  } //stay here until an interrupt comes in
}

   
//PAD Interrupt. Pressing any SW1-Sw4 debounce switche will toggle LED4 for a short period of time   

interrupt (((0x10000-Vportad)/2)-1) void PORTAD_ISR(void)
//interrupt VectorNumber_Vportad void PORTAD_ISR(void)  //another way declare interrupt
  {
    unsigned char x;
    for (x=0;x<30;x++)     //Upon PAD Interrupt the LED4 toggles for a short period 			
      {
       PTT = PTT ^ 0b10000000;       //toggle LED4 for short time 
      MSDelay(50);		    //During the toggling LED4, the LED1 stops toggling. Why? 		
        
      }
 

  PIF1AD = PIF1AD | 0b11110000; //clear PAD 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<1000;j++);
  }