TM4C123GH6PM: Having trouble setting PWM period

Hello,

I'm trying to make an LED blink on and off for 1 sec. with PWM. But no matter what I write in PWMGenPeriodSet and PWMPulseWidthSet, the LED is continuously on and never turns off. The code is below. Please help I really need this. Thanks in advance.

#include <stdint.h>
#include <stdbool.h>
#include <math.h>
#include "inc/hw_types.h"
#include "inc/hw_memmap.h"
#include "inc/hw_gpio.h"
#include "driverlib/sysctl.h"
#include "driverlib/gpio.h"
#include "driverlib/interrupt.h"
#include <inc/hw_ints.h>
#include "driverlib/timer.h"
#include "driverlib/pwm.h"
#include "driverlib/pin_map.h"
#include "driverlib/adc.h"
#include "driverlib/debug.h"

int main(void)
{

SysCtlClockSet(SYSCTL_SYSDIV_4|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);

SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF); 
SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM1);

SysCtlPWMClockSet(SYSCTL_PWMDIV_1);

HWREG(GPIO_PORTF_BASE + GPIO_O_LOCK) = GPIO_LOCK_KEY;
HWREG(GPIO_PORTF_BASE + GPIO_O_CR) = 0x01;

GPIOPinConfigure(GPIO_PF1_M1PWM5);
GPIOPinConfigure(GPIO_PF2_M1PWM6);
GPIOPinConfigure(GPIO_PF3_M1PWM7);

GPIOPinTypePWM(GPIO_PORTF_BASE,GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3);

PWMGenConfigure(PWM1_BASE,PWM_GEN_2,PWM_GEN_MODE_DOWN|PWM_GEN_MODE_NO_SYNC); 
PWMGenConfigure(PWM1_BASE,PWM_GEN_3,PWM_GEN_MODE_DOWN|PWM_GEN_MODE_NO_SYNC); 

PWMGenPeriodSet(PWM1_BASE,PWM_GEN_2,16000000);
PWMGenPeriodSet(PWM1_BASE,PWM_GEN_3,16000000);

PWMPulseWidthSet(PWM1_BASE,PWM_OUT_5,8000000);
PWMPulseWidthSet(PWM1_BASE,PWM_OUT_6,8000000);
PWMPulseWidthSet(PWM1_BASE,PWM_OUT_7,8000000);

PWMGenEnable(PWM1_BASE,PWM_GEN_2);
PWMGenEnable(PWM1_BASE,PWM_GEN_3);

PWMOutputState(PWM1_BASE, (PWM_OUT_5_BIT|PWM_OUT_6_BIT|PWM_OUT_7_BIT), true); 

while(1)
{

}

}