//Displaying Overflow Timer on LEDs of PORTT in C Language for HCS12G128 Tower Board with Codewarrior
//On TWR-S12G128 Tower module, 4 green LEDs are connected to PT7-PT4 
//They are active LOW. Make sure the jumers for all 4 LEDs (LED1-LED4) are set

//Modified from Example 9-28 in HCS12 book by Mazidi & Causey

//Use F7 to Make, F5 (Debug) to download, and F5 (Start) to run the program

//In CodeWarrior,make sure you are in Open Source BDM when downloading and running.
 
#include <hidef.h>      /* common defines and macros */
#include "derivative.h"      /* derivative-specific definitions */


void main(void) 
{
  /* put your own code here */
  
    unsigned char overflow = 0; 

    DDRT = 0xF0;    //PORTT as output
       	
   TSCR1 = 0x80;  //enable timer
   TSCR2 = 0x01;  //Prescaler=2 (Try 0-7 values to see changes on LEDs) 
  	   
   for(;;)
    { 
      TFLG2 = 0x80;  
      
      while (!(TFLG2 & TFLG2_TOF_MASK));  //wait for Timer Overflow
      //while ((TFLG2 &0x80)==0);          //instead of the above line you can use this one
      overflow = overflow + 1;            //keep adding the overflows
      PTT = ~overflow;                    // dump it on LEDs (invert the value because LEDs are low active)
    }					  //Notice it is showing only the upper 4 bits of PT7-PT4. 
					  //You can connect the lower pins of PT3-PT0 to LEDs on a breadboard and see all 8-bits 

}