Launchpad TM4C123GH6P.. LED blinking too fast

Hello, 

I'm just starting out embedded programming and chose this launchpad to be my first. I'm using Keil to blink a LED within a 1 second interval (ON for 1 second, OFF for 1 second) by using the Systick timer (Main clock, no PLL). However, it seems like the LED is blinking in 0.5 second intervals. 

Also, I tested in simulation mode using the logic analyzer in Keil, and according to the logic analyzer, the LED is blinking within 1 second intervals. I honestly have no idea what is going on.

Below is my code

#include "tm4c123gh6pm.h"

// Port F LED
#define LED_RED (1U << 1);
#define LED_BLUE (1U << 2);
#define LED_GREEN (1U << 3);

void PortF_Init(void);
void PLL_Init(void);
void SysTick_Init(void);
void Systick_delay(void);


int main(){

	PortF_Init();
	SysTick_Init();
	
	for(;;) {
		// Turn on RED LED
		GPIOF->DATA ^= LED_RED;
		Systick_delay();
		
	}
	return 0;
}

//
// Initializes Port F to allow SW1 as input, and RED, BLUE and GREEN LED as outut 
void PortF_Init(void) {
	SYSCTL->RCGCGPIO = (1U << 5); // Enable PortF Clock
	while( (SYSCTL->RCGCGPIO) == 0x00 ); // Wait for Clock to stabilize
	// Configure PF4 (SW1) as Input; PF1, PF2, PF3 as output
	GPIOF->DIR &= 0xFFFFFFEF;	// PF4 As Input 0b 1110 1111
	GPIOF->DIR |= 0x0000000E; // PF3, PF2, PF1 as output 0b 0000 1110
	// Clear Alternate Functions to set GPIO pins as GPIO
	GPIOF->AFSEL = 0x00000000;
	// Enable Pull up Resistor on SW1
	GPIOF->PUR |= (1U << 4);
	
	// Disable Analog Mode and Enable Digital Mode for GPIOF pins
	GPIOF->AMSEL &= 0x00000000;
	GPIOF->DEN |= 0x0000001E; // Digital Enable Port F pins 1 - 4 (bit[4:1])
}

//
// Initializes Systick timer
void SysTick_Init(void) {
	
	
	// 0. Disable Systick
	SysTick->CTRL &= 0x00;
	// 1. Program the value in the STRELOAD register.
	SysTick->LOAD = 16000000U;
	// 2. Clear the STCURRENT register by writing to it with any value.
	SysTick->VAL = 0U; 
	// 3. Configure the STCTRL register for the required operation.
	SysTick->CTRL |= (1U << 2); // Use System Clock (16 MHz)
	SysTick->CTRL |= (1U << 0); // Enable Systick
}

//
// Delay Timer Using Systick
// Will delay for 1 second
void Systick_delay(void) {

	// Write to VAL to reset Counter
	SysTick->VAL = 16000000U;
	// Wait while count flag is still 0
	while( (SysTick->CTRL  & 0x00010000) == 0x00 );
	
}

If someone can give me some advice, it would be greatly appreciated. Thanks