ADC sampling at 240kHz

EDIT: Removed Sleep(), as it is irrelevant to the question.

EDIT: Included relevant pre-processor definitions and cleaned up code representation.

EDIT: Fixed SysTick initialization, which did not affect the issue.

I am trying to collect data via the ADC at 240 kHz, and am not sure if I am setting up the clock and timer up correctly... I've been inputting a 10kHz sine wave, and getting data that looks like it's much higher frequency (about 100 kHz). Can someone either verify my config code below, or explain precisely how SysCtlClockSet() and TimerLoadSet() work (as in, how the numbers input to them convert to clock and timer frequency)?

When I run SysCtlClockGet(), I get 80 MHz, the maximum clock frequency. In order to look at the input, I have been putting the samples into a global uint32_t dataBuffer and graphing it.

#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <math.h>

#include "driverlib/adc.h"
#include "driverlib/gpio.h"
#include "driverlib/interrupt.h"
#include "driverlib/sysctl.h"
#include "driverlib/systick.h"
#include "driverlib/timer.h"

#include "inc/hw_adc.h"
#include "inc/hw_memmap.h"
#include "inc/hw_ints.h"

//*****************************************************************************
//
// Preprocessor Definitions
// ## Adjust Parameters Here!! ##
//
//*****************************************************************************

// Programmer-Designed Parameters (do not touch)
#define SAMPLE_RATE 240000      // Hz

#define ADC_SEQUENCER 3

#define DEBUG
//#undef DEBUG

//*****************************************************************************
//
// Global Variables
//
//*****************************************************************************

// Debugging variables
#ifdef DEBUG
int gBufferIndex;
static uint32_t gDataBuffer[400];
#endif

//*****************************************************************************
//
// Initialization/Configuration Functions
//
//*****************************************************************************

// Initialize global variables. //
void InitGVariables()
{
#ifdef DEBUG
    // Initialize debugging variables.
    gBufferIndex = 0;
#endif
}

// Initialize clock and timer. //
void InitTiming()
{
    // Initialize clock.
    SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_PLL | SYSCTL_XTAL_16MHZ | SYSCTL_OSC_MAIN);

    // Configure and enable timer.
    SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);
    while(!SysCtlPeripheralReady(SYSCTL_PERIPH_TIMER0));
    TimerConfigure(TIMER0_BASE, TIMER_CFG_PERIODIC);
    TimerLoadSet(TIMER0_BASE, TIMER_A, SysCtlClockGet()/SAMPLE_RATE);
    TimerEnable(TIMER0_BASE, TIMER_A);
    TimerControlTrigger(TIMER0_BASE, TIMER_A, true);

#ifdef DEBUG
    // Initialize SysTick.
    SysTickPeriodSet(10000000);
    SysTickEnable();
#endif
}

// Initialize GPIO pins. //
void InitGPIO()
{
    // Configure analog input pin.
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
    while(!SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOE));
    GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_3); // Pin 3 corresponds to channel 0.
}

// Initialize ADC. //
void InitADC()
{
    // Configure ADC sequencer.
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
    while(!SysCtlPeripheralReady(SYSCTL_PERIPH_ADC0));
    ADCSequenceConfigure(ADC0_BASE, ADC_SEQUENCER, ADC_TRIGGER_TIMER, 0);
    ADCSequenceStepConfigure(ADC0_BASE, ADC_SEQUENCER, 0, ADC_CTL_CH0 | ADC_CTL_IE | ADC_CTL_END);

    // Enable ADC interrupt.
    IntEnable(INT_ADC0SS3);
    ADCIntEnable(ADC0_BASE, ADC_SEQUENCER);
    IntMasterEnable();

    // Enable ADC sequencer.
    ADCSequenceEnable(ADC0_BASE, ADC_SEQUENCER);
}

//*****************************************************************************
//
// Interrupt Handlers
//
//*****************************************************************************

// Handle an ADC interrupt. //
void ADC0Seq3IntHandler()
{
#ifdef DEBUG
    uint32_t numCycles = SysTickValueGet();
#endif

    // Clear interrupt and get sample
    ADCIntClear(ADC0_BASE, ADC_SEQUENCER);
    uint32_t sample;
    ADCSequenceDataGet(ADC0_BASE, ADC_SEQUENCER, &sample);

    // Process data sample.

#ifdef DEBUG
    gBufferIndex = (gBufferIndex + 1) % 400;
    gDataBuffer[gBufferIndex] = sample;

    numCycles = SysTickValueGet() - numCycles;
    uint32_t clockRate = SysCtlClockGet();
#endif
}

//*****************************************************************************
//
// The main function.
//
//*****************************************************************************
int main(void)
{
    // Initialize everything.
    InitGVariables();
    InitTiming();
    InitGPIO();
    InitADC();

    while(1);
}