GIPO interrrupt on both edges

working with lm4f120h5qr launchpad. want to interface with hcsr04 sensor to launchpad without using "Stellarisware" and other libraries.

my code is as follows :

//This is to avoid doing the math everytime you do a reading
const double temp = 1.0/80.0;

//Stores the pulse length
extern volatile unsigned int pulse;

//Tells the main code if the a pulse is being read at the moment
extern volatile unsigned char echowait;

int main(void)
{

	PLL_Init(); //80mhz
	SysTick_Init();
	Init_Timer();
	Init_sensor();
	
	while(1)
	{
			
    //Checks if a pulse read is in progress
    if(echowait != 1)
			{
				//Does the required pulse of 10uS
				TriggerPulse();
				
					/*This makes the code wait for a reading to finish
					You can omit this part if you want the code to be non-blocking but
					reading is only ready when echowait=0.*/
				
				while(echowait != 0);

				//Converts the counter value to cm.
				pulse =(unsigned int)(temp * pulse);
				pulse = pulse / 58;

				//Prints out the distance measured.
				send_serial("distance = %2dcm \n" , pulse);
			}
      //wait about 10ms until the next reading.
      delay_ms(10);


	}

}
/*********************main end********************/
followinf functions are in different c file : 

volatile unsigned int pulse=0;

volatile unsigned char echowait=0;

void Init_sensor(void)
{
	volatile unsigned long delay;
	
	SYSCTL_RCGC2_R |= SYSCTL_RCGC2_GPIOA; // activate clock for port A
  delay = SYSCTL_RCGC2_R;
  GPIO_PORTA_AMSEL_R &= ~(TRIG_PIN | ECHO_PIN);      // disable analog functionality on PA5,PA6
  GPIO_PORTA_PCTL_R |= 0x00222211;//(GPIO_PORTA_PCTL_R&0x00FFFFFF)+0x33000000; // configure PA5 PA6 as GPIO
 GPIO_PORTA_DIR_R |= TRIG_PIN;     						 // make PA5 out
GPIO_PORTA_DIR_R &= ~ECHO_PIN;								 //make PA6 In
  //GPIO_PORTA_DR8R_R |= TRIG_PIN;    						 // enable 8 mA drive on PA5,6
  GPIO_PORTA_AFSEL_R &= ~(TRIG_PIN | ECHO_PIN);  // disable alt funct on PA5,6
  GPIO_PORTA_DEN_R = (TRIG_PIN | ECHO_PIN);     // enable digital I/O on PA5,6
GPIO_PORTA_PUR_R |= ECHO_PIN;     //     enable weak pull-up on PA
  GPIO_PORTA_IS_R &= ~ECHO_PIN;     //  PA6 is edge-sensitive
  GPIO_PORTA_IBE_R |= ECHO_PIN;    //      PA6 is  both edges
  GPIO_PORTA_ICR_R = ECHO_PIN;      //  clear flags PA6
  GPIO_PORTA_IM_R |= ECHO_PIN;      // arm interrupt on PA6
	NVIC_PRI7_R = (NVIC_PRI7_R&0xFF00FFFF)|0x00400000; // (g) priority 2
  NVIC_EN0_R = NVIC_EN0_INT0;      // enable interrupt 30 in NVIC
}

// Start the timers and interrupt frequency
void Init_Timer(void) 
{
	unsigned long volatile delay;
  delay = SYSCTL_RCGC2_R;
	SYSCTL_RCGCTIMER_R |= 0x04;   // 0) activate timer2
  delay = SYSCTL_RCGC2_R;
  TIMER2_CTL_R = 0x00000000;    // 1) disable timer2A during setup
  TIMER2_CFG_R = TIMER_CFG_32_BIT_TIMER;    // 2) configure for 32-bit mode
  TIMER2_TAMR_R = TIMER_TAMR_TAMR_PERIOD;   // 3) configure for periodic mode, default down-count settings
  TIMER2_TAILR_R = 0xFFFFFFFF;//((80000000 / 1000000) * 10);    // 4) reload value 10us
  TIMER2_TAPR_R = 0;            // 5) bus clock resolution
  TIMER2_CTL_R = 0x00000001;    // enable timer2A
}

void EchoPulseHandler(void) //This ISR executes when it detects the end of the echo pulse
{
	unsigned int status = 0;
	status = GPIO_PORTA_MIS_R;
		GPIO_PORTA_ICR_R = 0x01;  // acknowledge flag0	
	 /*
    If it's a rising edge then set he timer to 0
    It's in periodic mode so it was in some random value
  */
	//if echo pin high means burst is receiv to echo till echo pin gose low
  if(( status & ECHO_PIN) == ECHO_PIN ) //if high
		{
			TIMER2_TAR_R = 0; 				//Loads value 0 into the timer.
			TIMER2_CTL_R = 0x00000001;    // enable timer2A
			echowait=1;
		}
  
  //  If it's a falling edge that was detected, then get the value of the counter
  
  else  
		{
    pulse = TIMER2_TAV_R; 				//record value
    TIMER2_CTL_R = 0x00000000;    // disable timer2A
    echowait=0;
		}
}
//This executes the trigger pulse
void TriggerPulse(void)
{

		TRIG_PIN_HIGH 		//Set Trigger pin HIGH
		delay_us(10); 		//10us
		TRIG_PIN_LOW			//Set Trigger LOW
		delay_us(10); 		//10us	
}
}

1)
the  problem is  falling edge interrupt doesn't occurred , the ISR stuck in raising edge.

i think there is some issue while initialization of port A and ECHO PIN

trigger pin is working ok.

2)

the other thing is when raising edge occurred the counter will be reset but its not.

also i tried   TAV_R but still counter value not reset .

tested  some stellarisware example on the same pins(with PORTA) with sensor , its measure the accurate distance.