diff --git a/main.c b/main.c
index 23436a4..676702e 100644
--- a/main.c
+++ b/main.c
@@ -1,2 +1,11 @@
 #include <stdint.h>
 #include "tm4c123gh6pm.h"
+
+#define STCTRL *((volatile uint32_t *) 0xE000E010)        // Control and status
+#define STRELOAD *((volatile uint32_t *) 0xE000E014)      // Reload value
+#define STCURRENT *((volatile uint32_t *) 0xE000E018)     // Current value
+
+#define ENABLE (1 << 0)      // Bit 0 of CSR to enable the timer
+#define CLKINT (1 << 2)      // Bit 2 of CSR to specify CPU clock
+#define CLOCK_HZ 16000000    // Clock frequency of EK-TM4C123GXL
+#define SYSTICK_RELOAD_VALUE(us) ((CLOCK_HZ / 1000000) * (us) - 1)   // SysTick reload value in microseconds based on clock frequency