PLL_Init.h

// The #define statement SYSDIV2 in PLL.h
// initializes the PLL to the desired frequency.

#define SYSCTL_RIS_R            (*((volatile unsigned long *)0x400FE050))
#define SYSCTL_RIS_PLLLRIS      0x00000040  // PLL Lock Raw Interrupt Status
#define SYSCTL_RCC_R            (*((volatile unsigned long *)0x400FE060))
#define SYSCTL_RCC_XTAL_M       0x000007C0  // Crystal Value
#define SYSCTL_RCC_XTAL_6MHZ    0x000002C0  // 6 MHz Crystal
#define SYSCTL_RCC_XTAL_8MHZ    0x00000380  // 8 MHz Crystal
#define SYSCTL_RCC_XTAL_16MHZ   0x00000540  // 16 MHz Crystal
#define SYSCTL_RCC2_R           (*((volatile unsigned long *)0x400FE070))
#define SYSCTL_RCC2_USERCC2     0x80000000  // Use RCC2
#define SYSCTL_RCC2_DIV400      0x40000000  // Divide PLL as 400 MHz vs. 200
                                            // MHz
#define SYSCTL_RCC2_SYSDIV2_M   0x1F800000  // System Clock Divisor 2
#define SYSCTL_RCC2_SYSDIV2LSB  0x00400000  // Additional LSB for SYSDIV2
#define SYSCTL_RCC2_PWRDN2      0x00002000  // Power-Down PLL 2
#define SYSCTL_RCC2_BYPASS2     0x00000800  // PLL Bypass 2
#define SYSCTL_RCC2_OSCSRC2_M   0x00000070  // Oscillator Source 2
#define SYSCTL_RCC2_OSCSRC2_MO  0x00000000  // MOSC

// The #define statement SYSDIV2 initializes
// the PLL to the desired frequency.
#define SYSDIV2 4
// bus frequency is 400MHz/(SYSDIV2+1) = 400MHz/(4+1) = 80 MHz

// configure the system to get its clock from the PLL
void PLL_Init(void);