TM4C123GH6PM: AHB set up and APB

Several suggestions. First, did you configure GIO Port F to use AHB bus in System Control register 9? Second, why are you using 0x3FC as the offset for the DATA register. The documented offset is 0x000. Third, why are you defining the DATA register as an unsigned long? It should not be written to by anything larger than 32 bits wide.

I highly encourage the use of proven examples and library routines. When you create your own register definitions you allow the opportunity for making these kinds of mistakes and you make it more difficult for people to help you. I took the simple example "blinky" for the EK-TM4C123G board and changed it to use AHB writes to port F by adding a TivaWare call to SysCtlGPIOAHBEnable() and replacing three time GPIO_PORTF_BASE with GPIO_PORTF_AHB_BASE.

#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_memmap.h"
#include "driverlib/debug.h"
#include "driverlib/gpio.h"
#include "driverlib/sysctl.h"

//*****************************************************************************
//
//! \addtogroup example_list
//! <h1>Blinky (blinky)</h1>
//!
//! A very simple example that blinks the on-board LED using direct register
//! access.
//
//*****************************************************************************

//*****************************************************************************
//
// The error routine that is called if the driver library encounters an error.
//
//*****************************************************************************
#ifdef DEBUG
void
__error__(char *pcFilename, uint32_t ui32Line)
{
    while(1);
}
#endif

//*****************************************************************************
//
// Blink the on-board LED.
//
//*****************************************************************************
int
main(void)
{
    volatile uint32_t ui32Loop;

    //
    // Enable the GPIO port that is used for the on-board LED.
    //
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);

    //
    // Check if the peripheral access is enabled.
    //
    while(!SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOF))
    {
    }

    // Configure GIO Port F to use AHB bus
    SysCtlGPIOAHBEnable(SYSCTL_PERIPH_GPIOF);
    //
    // Enable the GPIO pin for the LED (PF3).  Set the direction as output, and
    // enable the GPIO pin for digital function.
    //
    GPIOPinTypeGPIOOutput(GPIO_PORTF_AHB_BASE, GPIO_PIN_3);

    //
    // Loop forever.
    //
    while(1)
    {
        //
        // Turn on the LED.
        //
        GPIOPinWrite(GPIO_PORTF_AHB_BASE, GPIO_PIN_3, GPIO_PIN_3);

        //
        // Delay for a bit.
        //
        for(ui32Loop = 0; ui32Loop < 200000; ui32Loop++)
        {
        }

        //
        // Turn off the LED.
        //
        GPIOPinWrite(GPIO_PORTF_AHB_BASE, GPIO_PIN_3, 0x0);

        //
        // Delay for a bit.
        //
        for(ui32Loop = 0; ui32Loop < 200000; ui32Loop++)
        {
        }
    }
}