diff --git a/src/rk65c02.h b/src/rk65c02.h
index 0370181..977e9a4 100644
--- a/src/rk65c02.h
+++ b/src/rk65c02.h
@@ -6,39 +6,52 @@
 
 #include "bus.h"
 
+/**
+ * @brief Current state of the emulator.
+ */
 typedef enum {
-	STOPPED,
-	RUNNING,
-	STEPPING	/* XXX: how to implement? */
+	STOPPED,	/**< Stopped. */
+	RUNNING,	/**< Running. */
+	STEPPING	/**< Stepping. */
 } emu_state_t;
 
+/**
+ * @brief Enum describing why emulation stopped.
+ */
 typedef enum {
-	STP,		/* due to 65C02 STP instruction */
-	WAI,		/* waiting for interrupt */
-	BREAKPOINT,	/* due to breakpoint set */
-	WATCHPOINT,	/* due to watchpoint set */
-	STEPPED,	/* stepped appropriate number of instructions */
-	HOST,		/* due to host stop function called */
-	EMUERROR	/* due to emulator error */
+	STP,		/**< Due to 65C02 STP instruction. */
+	WAI,		/**< Waiting for interrupt (WAI instruction). */
+	BREAKPOINT,	/**< Due to breakpoint set. */
+	WATCHPOINT,	/**< Due to watchpoint set (not implemented). */
+	STEPPED,	/**< Stepped appropriate number of instructions. */
+	HOST,		/**< Due to host stop function called. */
+	EMUERROR	/**< Due to emulator error. */
 } emu_stop_reason_t;
 
+/**
+ * @brief Current state of emulated CPU registers.
+ */
 struct reg_state {
-	uint8_t A;      /* accumulator */
-	uint8_t X;      /* index X */
-	uint8_t Y;      /* index Y */
+	uint8_t A;	/**< Accumulator. */
+	uint8_t X;      /**< Index X. */
+	uint8_t Y;      /**< Index Y. */
 
-	uint16_t PC;    /* program counter */
-	uint8_t SP;     /* stack pointer */
-	uint8_t P;      /* status */
+	uint16_t PC;    /**< Program counter. */
+	uint8_t SP;     /**< Stack pointer. */
+	uint8_t P;      /**< Status. */
 };
 
 typedef struct reg_state reg_state_t;
 
 #define P_CARRY 0x1
 #define P_ZERO 0x2
+/** Status register flag: IRQ disabled */
 #define P_IRQ_DISABLE 0x4
+/** Status register flag: BCD mode */
 #define P_DECIMAL 0x8
+/** Status register flag: BRK was the cause of interrupt */
 #define P_BREAK 0x10
+/** Status register flag: Undefined (always 1) */
 #define P_UNDEFINED 0x20
 #define P_SIGN_OVERFLOW 0x40
 #define P_NEGATIVE 0x80
@@ -64,17 +77,20 @@ typedef struct trace_t {
 	struct trace_t *prev,*next;
 } trace_t;
 
+/**
+ * @brief Instance of the emulator.
+ */
 struct rk65c02emu {
 	emu_state_t state;
 	bus_t *bus;
 	reg_state_t regs;
 	emu_stop_reason_t stopreason;
-	bool irq;		/* interrupt request line state, true is asserted */
+	bool irq;		/**< Interrupt request line state, true is asserted. */
 
-	breakpoint_t *bps_head;	/* pointer to linked list with breakpoints  */
-	bool runtime_disassembly; /* disassemble code when emulator is running */
-	bool trace;		/* tracing mode enable/disable */
-	trace_t *trace_head;	/* pointer to linked list with trace log */
+	breakpoint_t *bps_head;	/**< Pointer to linked list with breakpoints. */
+	bool runtime_disassembly; /**< Disassemble code when emulator is running. */
+	bool trace;		/**< Tracing mode enable/disable. */
+	trace_t *trace_head;	/**< Pointer to linked list with trace log. */
 };
 
 typedef struct rk65c02emu rk65c02emu_t;
@@ -93,11 +109,12 @@ void rk65c02_start(rk65c02emu_t *);
  * @brief Execute as many instructions as specified in steps argument.
  */
 void rk65c02_step(rk65c02emu_t *, uint16_t);
+
 char *rk65c02_regs_string_get(reg_state_t);
 void rk65c02_dump_regs(reg_state_t);
 void rk65c02_dump_stack(rk65c02emu_t *, uint8_t);
 
-/*
+/**
  * @brief Assert the IRQ line.
  */
 void rk65c02_assert_irq(rk65c02emu_t *);