diff --git a/src/flash.h b/src/flash.h
new file mode 100644
index 0000000..780cee5
--- /dev/null
+++ b/src/flash.h
@@ -0,0 +1,35 @@
+#ifndef FLASH_H_
+#define FLASH_H_
+
+#include <inttypes.h>
+
+struct flash {
+  volatile uint32_t ACR;      // Flash access control register
+  volatile uint32_t KEYR;     // Flash key register
+  volatile uint32_t OPTKEYR;  // Flash option key register
+  volatile uint32_t SR;       // Flash status register
+  volatile uint32_t CR;       // Flash control register
+  volatile uint32_t OPTCR;    // Flash option control register
+};
+
+#define FLASH_BASE_ADDR (0x40023C00U)
+#define FLASH ((struct flash *) FLASH_BASE_ADDR)
+
+// ACR Register
+// Data cache enable
+
+#define FLASH_ACR_DCEN_BIT 10
+#define FLASH_ACR_DCEN_ENABLE (1 <<FLASH_ACR_DCEN_BIT)
+
+// Instruction cache enable
+#define FLASH_ACR_ICEN_BIT 9
+#define FLASH_ACR_ICEN_ENABLE (1 <<FLASH_ACR_ICEN_BIT)
+
+// Latency
+#define FLASH_ACR_LATENCY_3_WAIT_STATES (0x0111)
+
+#define FLASH_ACR_LATENCY_BIT 0 // Bits [3:0]
+#define FLASH_ACR_LATENCY_MASK (0b1111)
+#define FLASH_ACR_LATENCY(latency) ((latency & FLASH_ACR_LATENCY_MASK) << FLASH_ACR_LATENCY_BIT)
+
+#endif