PWM Code Draft For Lab 4, Session 7

main.c

#include <hidef.h>      /* common defines and macros */ 
#include <mc9s12c32.h>     /* derivative information */ 
#pragma LINK_INFO DERIVATIVE "mc9s12c32" 
#pragma CODE_SEG DEFAULT 
#define PWMDTY0 DUTY_CYCLE // These HCS12 defines are too cryptic!

// ################
// Global Variables
// ################
int duty_perc = 0;


// ################
// Functions
// ################

void pwm_setup( void ){
	// This function sets up Clock 1 and PWM Channel 5.
	// Desired PWM Frequency = Bus Clock (4 MHz) / PeriodValue (250) / PrescaleA (4) / ScaleA (1)
	PWME			= 0x01;  // Enable PWM.
	PWMCLK		= 0x01;  // (1 or 2) Which of the two PWM clocks to use.
	PWMPRCLK		= 0x04;  // PWM Prescale Clock Select.
   PWMSCLA		= 0x01;  // PWM scale register for Clock SA.
   PWMPER5		= 0xFA;  // PWM Channel 5 Period. Set to 250.
   PWMDTY5		= 0xFA;  // PWM Channel 5 Duty Cycle: ( Duty / Period) * 100  = %duty cycle
}

void set_duty_cycle( int duty_perc ){
	// Update the Duty Cycle. Receive values betwen 0 and 100;
	if( duty_perc > 0x00 && duty_perc <= 0xFA){
		DUTY_CYCLE = ( (duty_perc * period )/ 100);
	}else{
		// If invalid input, stop the motor.
		DUTY_CYCLE = 0;
	}
}

void main(void)  
{ 
   
  //Enabling portT for PWM0 
  /*  MODRR =0x01;       
         The  line MODRR=0x01 may not be     
         necessary if your PWM  
         in not multiplexed with the Timer module.  
         Check the block diagram of your circuit. 
   */ 
	while(1);
}