diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..9eca6c8
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+*.a
+*.o
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..d9c168c
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,23 @@
+CROSS :=
+CC := $(CROSS)gcc
+CFLAGS := -Os -ggdb -g3 \
+		  -Wall -Wextra -pedantic -Werror
+
+CSRC := $(wildcard src/*.c)
+COBJ := $(patsubst %.c,%.o,$(CSRC))
+
+all: lib430core.a
+
+clean:
+	@echo "  CLEAN"
+	@rm -f lib430core.a $(COBJ)
+
+lib430core.a: $(COBJ)
+	@echo "  AR      " $@
+	@$(CROSS)ar rc $@ $(COBJ)
+	@$(CROSS)size -t $@
+
+.c.o:
+	@echo "  CC      " $<
+	@$(CC) $(CFLAGS) -c $< -o $@
+
diff --git a/link.ld b/link.ld
new file mode 100644
index 0000000..582fb5f
--- /dev/null
+++ b/link.ld
@@ -0,0 +1,15 @@
+SECTIONS {
+	. = 0x0000;
+	.text : {
+		* (.text);
+		. = ALIGN(8);
+		* (.rodata);
+	}
+	. = ALIGN(8);
+	.data : {
+		* (.data);
+		. = ALIGN(8);
+		* (.bss);
+	}
+}
+
diff --git a/src/core.c b/src/core.c
new file mode 100644
index 0000000..c29fe96
--- /dev/null
+++ b/src/core.c
@@ -0,0 +1,258 @@
+#include "core.h"
+
+#include <stdint.h>
+
+#define MSP430_SR_C (1 << 0)
+#define MSP430_SR_Z (1 << 1)
+#define MSP430_SR_N (1 << 2)
+#define MSP430_SR_V (1 << 8)
+
+// r0 = pc
+// r1 = sp
+// r2 = sr
+
+static int msp430_do_cycle_jump(msp430_t *state, uint16_t opcode);
+int msp430_do_cycle_single_operand(msp430_t *state, uint16_t opcode);
+int msp430_do_cycle_dual_operand(msp430_t *state, uint16_t opcode);
+int msp430_do_cycle_single_operand_byte(msp430_t *state, uint16_t opcode);
+int msp430_do_cycle_dual_operand_byte(msp430_t *state, uint16_t opcode);
+
+uint16_t *msp430_do_cycle_get_single_operand(msp430_t *state, uint16_t opcode);
+uint16_t *msp430_do_cycle_get_source_operand(msp430_t *state, uint16_t opcode);
+uint16_t *msp430_do_cycle_get_dest_operand(msp430_t *state, uint16_t opcode);
+
+static inline int msp430_get_opcode_bw(uint16_t opcode);
+
+void msp430_init_state(msp430_t *state, void *mem)
+{
+	for (int i = 0; i < 16; ++i)
+		state->reg[i] = 0;
+	state->mem = mem;
+}
+
+int msp430_do_cycle(msp430_t *state)
+{
+	uint16_t pc = state->reg[0];
+	uint16_t opcode = *((uint16_t *)(state->mem + pc));
+
+	// Check for program end...
+	if (opcode == 0x4130 && state->reg[1] == 0)
+		return 1;
+
+	state->reg[0] = pc + 2;
+
+	int ret;
+	if ((opcode & 0xE000) == 0x2000) {
+		ret = msp430_do_cycle_jump(state, opcode);
+	} else {
+		int bw = msp430_get_opcode_bw(opcode);
+		if (bw == 0) {
+			if ((opcode & 0xFC00) == 0x1000)
+				ret = msp430_do_cycle_single_operand(state, opcode);
+			else
+				ret = msp430_do_cycle_dual_operand(state, opcode);
+		} else {
+			if ((opcode & 0xFC00) == 0x1000)
+				ret = msp430_do_cycle_single_operand_byte(state, opcode);
+			else
+				ret = msp430_do_cycle_dual_operand_byte(state, opcode);
+		}
+	}
+
+	return ret;
+}
+
+static void msp430_jump_to_offset(msp430_t *state, uint16_t opcode)
+{
+	uint16_t addr = opcode & 0x3FF;
+	if (addr & (1 << 9))
+		addr |= 0xFC00;
+	int16_t saddr = (int16_t)addr * 2;
+	state->reg[0] += saddr;
+}
+
+int msp430_do_cycle_jump(msp430_t *state, uint16_t opcode)
+{
+	// PC to become PC + ((opcode & 0x3FF) << 1)
+	switch ((opcode & 0x01C0) >> 10) {
+	case 0:
+		// JNE/JZ
+		if ((state->reg[2] & MSP430_SR_Z) == 0)
+			msp430_jump_to_offset(state, opcode);
+		break;
+	case 1:
+		// JEQ/JZ
+		if ((state->reg[2] & MSP430_SR_Z) == MSP430_SR_Z)
+			msp430_jump_to_offset(state, opcode);
+		break;
+	case 2:
+		// JNC/JLO
+		if ((state->reg[2] & MSP430_SR_C) == 0)
+			msp430_jump_to_offset(state, opcode);
+		break;
+	case 3:
+		// JC/JHS
+		if ((state->reg[2] & MSP430_SR_C) == MSP430_SR_C)
+			msp430_jump_to_offset(state, opcode);
+		break;
+	case 4:
+		// JN
+		if ((state->reg[2] & MSP430_SR_N) == MSP430_SR_N)
+			msp430_jump_to_offset(state, opcode);
+		break;
+	case 5: {
+		// JGE
+		uint16_t flags = state->reg[2] & (MSP430_SR_N | MSP430_SR_V);
+		if (flags == 0 || flags == (MSP430_SR_N | MSP430_SR_V))
+			msp430_jump_to_offset(state, opcode);
+		break; }
+	case 6: {
+		// JL
+		uint16_t flags = state->reg[2] & (MSP430_SR_N | MSP430_SR_V);
+		if (flags == MSP430_SR_N || flags == MSP430_SR_V)
+			msp430_jump_to_offset(state, opcode);
+		break; }
+	case 7:
+		// JMP
+		msp430_jump_to_offset(state, opcode);
+		break;
+	default:
+		return -1;
+	}
+
+	return 0;
+}
+
+uint16_t *msp430_do_cycle_get_operand(msp430_t *state, int AS, int BW, int SOURCE)
+{
+	static uint16_t constants[6] = {
+		0, 1, 2, -1, 4, 8
+	};
+
+	if (SOURCE == 0) {
+		if (AS == 1) {
+			// Operand at PC + X
+			// X = word after PC
+			uint16_t offset = *((uint16_t *)(state->mem + state->reg[0]));
+			uint16_t *ret = (uint16_t *)(state->mem + state->reg[0] + offset);
+			state->reg[0] += 2;
+			return ret;
+		} else if (AS == 3) {
+			// Operand is X
+			uint16_t *ret = (uint16_t *)(state->mem + state->reg[0]);
+			state->reg[0] += 2;
+			return ret;
+		}
+	}
+
+	if (SOURCE == 2) {
+		switch (AS) {
+		case 0:
+			// R2
+			return &state->reg[2];
+			break;
+		case 1: {
+			// Operand at X
+			uint16_t offset = *((uint16_t *)(state->mem + state->reg[0]));
+			uint16_t *ret = (uint16_t *)(state->mem + offset);
+			state->reg[0] += 2;
+			return ret;
+			break; }
+		case 2:
+			return &constants[4];
+			break;
+		case 3:
+			return &constants[5];
+			break;
+		}
+	} else if (SOURCE == 3) {
+		// Constants
+		return &constants[AS];
+	} else {
+		switch (AS) {
+		case 0:
+			// Register
+			return &state->reg[SOURCE];
+			break;
+		case 1: {
+			// Operand at Rn + X
+			uint16_t offset = *((uint16_t *)(state->mem + state->reg[0]));
+			uint16_t *ret = (uint16_t *)(state->mem + state->reg[SOURCE] + offset);
+			state->reg[0] += 2;
+			return ret;
+			break; }
+		case 2:
+			// Operand at Rn
+			return (uint16_t *)(state->mem + state->reg[SOURCE]);
+			break;
+		case 3: {
+			// Operand at Rn, increment Rn
+			uint16_t *ret = (uint16_t *)(state->mem + state->reg[SOURCE]);
+			state->reg[SOURCE] += BW ? 1 : 2;
+			return ret;
+			break; }
+		}
+	}
+
+	return 0; // Failed...
+}
+
+inline int msp430_get_opcode_bw(uint16_t opcode)
+{
+	return opcode & (1 << 6);
+}
+
+uint16_t *msp430_do_cycle_get_single_operand(msp430_t *state, uint16_t opcode)
+{
+	return msp430_do_cycle_get_operand(state,
+		/* AS */     (opcode & 0x30) >> 4,
+		/* BW */     msp430_get_opcode_bw(opcode),
+		/* SOURCE */ (opcode & 0xF));
+}
+
+uint16_t *msp430_do_cycle_get_source_operand(msp430_t *state, uint16_t opcode)
+{
+	return msp430_do_cycle_get_operand(state,
+		/* AS */     (opcode & 0x30) >> 4,
+		/* BW */     msp430_get_opcode_bw(opcode),
+		/* SOURCE */ (opcode & 0xF00) >> 8);
+}
+uint16_t *msp430_do_cycle_get_dest_operand(msp430_t *state, uint16_t opcode)
+{
+	int AD = opcode & 0x80;
+	int DEST = opcode & 0xF;
+
+	if (AD == 0) {
+		// Byte operation? Clear MSB.
+		if (msp430_get_opcode_bw(opcode) == 0) {
+			return &state->reg[DEST];
+		} else {
+			uint16_t *ret = &state->reg[DEST];
+			*ret &= 0xFF;
+			return ret;
+		}
+	} else {
+		if (DEST == 0) {
+			// dest at PC + X
+			uint16_t offset = *((uint16_t *)(state->mem + state->reg[0]));
+			uint16_t *ret = (uint16_t *)(state->mem + state->reg[0] + offset);
+			state->reg[0] += 2;
+			return ret;
+		} else if (DEST == 2) {
+			// dest at X
+			uint16_t offset = *((uint16_t *)(state->mem + state->reg[0]));
+			uint16_t *ret = (uint16_t *)(state->mem + offset);
+			state->reg[0] += 2;
+			return ret;
+		} else {
+			// dest at Rn + X
+			uint16_t offset = *((uint16_t *)(state->mem + state->reg[0]));
+			uint16_t *ret = (uint16_t *)(state->mem + state->reg[DEST] + offset);
+			state->reg[0] += 2;
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
diff --git a/src/core.h b/src/core.h
new file mode 100644
index 0000000..2a320a1
--- /dev/null
+++ b/src/core.h
@@ -0,0 +1,15 @@
+#ifndef CORE_H
+#define CORE_H
+
+#include <stdint.h>
+
+typedef struct {
+	uint16_t reg[16];
+	uint8_t *mem;
+} msp430_t;
+
+void msp430_init_state(msp430_t *state, void *mem);
+int msp430_do_cycle(msp430_t *state);
+
+#endif // CORE_H
+
diff --git a/src/do_cycle_byte.c b/src/do_cycle_byte.c
new file mode 100644
index 0000000..247d3b4
--- /dev/null
+++ b/src/do_cycle_byte.c
@@ -0,0 +1,214 @@
+#include <stdint.h>
+
+#define MSP430_SR_C (1 << 0)
+#define MSP430_SR_Z (1 << 1)
+#define MSP430_SR_N (1 << 2)
+#define MSP430_SR_V (1 << 8)
+
+// r0 = pc
+// r1 = sp
+// r2 = sr
+typedef struct {
+	uint16_t reg[16];
+	uint8_t *mem;
+} msp430_t;
+
+extern uint16_t *msp430_do_cycle_get_single_operand(msp430_t *state, uint16_t opcode);
+extern uint16_t *msp430_do_cycle_get_source_operand(msp430_t *state, uint16_t opcode);
+extern uint16_t *msp430_do_cycle_get_dest_operand(msp430_t *state, uint16_t opcode);
+
+int msp430_do_cycle_single_operand_byte(msp430_t *state, uint16_t opcode)
+{
+	uint8_t *operand = (uint8_t *)msp430_do_cycle_get_single_operand(state, opcode);
+	if (operand == 0)
+		return -1;
+
+	switch ((opcode & 0x0380) >> 7) {
+	case 0: {
+		// RRC
+		uint8_t res = *operand;
+		uint16_t sr = 0;
+		if (res & 1)
+			sr |= MSP430_SR_C;
+		res >>= 1;
+		if (state->reg[2] & MSP430_SR_C)
+			res |= 0x80;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((int8_t)res < 0)
+			sr |= MSP430_SR_N;
+		*operand = res;
+		state->reg[2] = sr;
+		break; }
+	case 2: {
+		// RRA
+		uint8_t res = *operand;
+		uint16_t sr = 0;
+		if (res & 1)
+			sr |= MSP430_SR_C;
+		res >>= 1;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((int8_t)res < 0)
+			sr |= MSP430_SR_N;
+		*operand = res;
+		state->reg[2] = sr;
+		break; }
+	case 4: {
+		// PUSH
+		uint16_t sp = state->reg[1] - 2;
+		*((uint16_t *)(state->mem + sp)) = *operand;
+		state->reg[1] = sp;
+		break; }
+	default:
+		return -1;
+		break;
+	}
+
+	return 0;
+}
+
+int msp430_do_cycle_dual_operand_byte(msp430_t *state, uint16_t opcode)
+{
+	uint8_t *src = (uint8_t *)msp430_do_cycle_get_source_operand(state, opcode);
+	uint8_t *dst = (uint8_t *)msp430_do_cycle_get_dest_operand(state, opcode);
+	if (src == 0 || dst == 0)
+		return -1;
+
+	switch ((opcode & 0xF000) >> 12) {
+	case 4:
+		// MOV
+		*dst = *src;
+		break;
+	case 5: {
+		// ADD
+		uint16_t res = *src + *dst;
+		uint16_t sr = 0;
+		if ((int8_t)res < 0)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((res & 0xFF00) != 0)
+			sr |= MSP430_SR_C;
+		if (((*src & 0x80) ^ (*src & 0x80)) == 0 && (*src & 0x80) != (res & 0x80))
+			sr |= MSP430_SR_V;
+		*dst = res & 0xFF;
+		state->reg[2] =	sr;
+		break; }
+	case 6: {
+		// ADDC
+		uint16_t res = *src + *dst + (state->reg[2] & MSP430_SR_C);
+		uint16_t sr = 0;
+		if ((int8_t)res < 0)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((res & 0xFF00) != 0)
+			sr |= MSP430_SR_C;
+		if (((*src & 0x80) ^ (*src & 0x80)) == 0 && (*src & 0x80) != (res & 0x80))
+			sr |= MSP430_SR_V;
+		*dst = res & 0xFF;
+		state->reg[2] =	sr;
+		break; }
+	case 7: {
+		// SUBC
+		uint16_t res = *dst + ~(*src) + (state->reg[2] & MSP430_SR_C);
+		uint16_t sr = 0;
+		if ((int8_t)res < 0)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((res & 0xFF00) != 0)
+			sr |= MSP430_SR_C;
+		if (((*src & 0x80) ^ (*src & 0x80)) == 0 && (*src & 0x80) != (res & 0x80))
+			sr |= MSP430_SR_V;
+		*dst = res & 0xFF;
+		state->reg[2] =	sr;
+		break; }
+	case 8: {
+		// SUB
+		uint16_t res = *dst + ~(*src) + 1;
+		uint16_t sr = 0;
+		if ((int8_t)res < 0)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((res & 0xFF00) != 0) // TODO confirm
+			sr |= MSP430_SR_C;
+		if (((*src & 0x80) ^ (*src & 0x80)) == 0 && (*src & 0x80) != (res & 0x80))
+			sr |= MSP430_SR_V;
+		*dst = res & 0xFF;
+		state->reg[2] =	sr;
+		break; }
+	case 9: {
+		// CMP
+		uint16_t res = *dst + ~(*src) + 1;
+		uint16_t sr = 0;
+		if ((int8_t)res < 0)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((res & 0xFF00) != 0)
+			sr |= MSP430_SR_C;
+		if (((*src & 0x80) ^ (*src & 0x80)) == 0 && (*src & 0x80) != (res & 0x80))
+			sr |= MSP430_SR_V;
+		state->reg[2] =	sr;
+		break; }
+	case 10:
+		// DADD TODO
+		break;
+	case 11: {
+		// BIT
+		uint8_t res = *dst & *src;
+		uint16_t sr = 0;
+		if (res & 0x80)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if (res != 0)
+			sr |= MSP430_SR_C;
+		state->reg[2] =	sr;
+		break; }
+	case 12:
+		// BIC
+		*dst &= ~(*src);
+		break;
+	case 13:
+		// BIS
+		*dst |= *src;
+		break;
+	case 14: {
+		// XOR
+		uint8_t res = *dst ^ *src;
+		uint16_t sr = 0;
+		if (res & 0x80)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if (res != 0)
+			sr |= MSP430_SR_C;
+		if ((*dst & 0x80) && (*src & 0x80))
+			sr |= MSP430_SR_V;
+		*dst = res;
+		state->reg[2] =	sr;
+		break; }
+	case 15: {
+		// AND
+		uint8_t res = *dst & *src;
+		uint16_t sr = 0;
+		if (res & 0x80)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if (res != 0)
+			sr |= MSP430_SR_C;
+		*dst = res;
+		state->reg[2] =	sr;
+		break; }
+	default:
+		return -1;
+	}
+
+	return 0;
+}
+
diff --git a/src/do_cycle_word.c b/src/do_cycle_word.c
new file mode 100644
index 0000000..2599d13
--- /dev/null
+++ b/src/do_cycle_word.c
@@ -0,0 +1,246 @@
+#include <stdint.h>
+
+#define MSP430_SR_C (1 << 0)
+#define MSP430_SR_Z (1 << 1)
+#define MSP430_SR_N (1 << 2)
+#define MSP430_SR_V (1 << 8)
+
+// r0 = pc
+// r1 = sp
+// r2 = sr
+typedef struct {
+	uint16_t reg[16];
+	uint8_t *mem;
+} msp430_t;
+
+extern uint16_t *msp430_do_cycle_get_single_operand(msp430_t *state, uint16_t opcode);
+extern uint16_t *msp430_do_cycle_get_source_operand(msp430_t *state, uint16_t opcode);
+extern uint16_t *msp430_do_cycle_get_dest_operand(msp430_t *state, uint16_t opcode);
+
+int msp430_do_cycle_single_operand(msp430_t *state, uint16_t opcode)
+{
+	uint16_t *operand = msp430_do_cycle_get_single_operand(state, opcode);
+	if (operand == 0)
+		return -1;
+
+	switch ((opcode & 0x0380) >> 7) {
+	case 0: {
+		// RRC
+		uint16_t res = *operand;
+		uint16_t sr = 0;
+		if (res & 1)
+			sr |= MSP430_SR_C;
+		res >>= 1;
+		if (state->reg[2] & MSP430_SR_C)
+			res |= 0x8000;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((int16_t)res < 0)
+			sr |= MSP430_SR_N;
+		*operand = res;
+		state->reg[2] = sr;
+		break; }
+	case 1: {
+		// SWPB
+		uint16_t swapped = ((*operand & 0xFF00) >> 8) | ((*operand & 0x00FF) << 8);
+		*operand = swapped;
+		break; }
+	case 2: {
+		// RRA
+		uint16_t res = *operand;
+		uint16_t sr = 0;
+		if (res & 1)
+			sr |= MSP430_SR_C;
+		res >>= 1;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((int16_t)res < 0)
+			sr |= MSP430_SR_N;
+		*operand = res;
+		state->reg[2] = sr;
+		break; }
+	case 3: {
+		// SXT
+		uint16_t sr = 0;
+		uint16_t res = (*operand & 0x80) ? (*operand | 0xFF00) : *operand;
+		if ((int16_t)res < 0)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if (res != 0)
+			sr |= MSP430_SR_C;
+		*operand = res;
+		state->reg[2] = sr;
+		break; }
+	case 4: {
+		// PUSH
+		uint16_t sp = state->reg[1] - 2;
+		*((uint16_t *)(state->mem + sp)) = *operand;
+		state->reg[1] = sp;
+		break; }
+	case 5: {
+		// CALL
+		uint16_t sp = state->reg[1] - 2;
+		*((uint16_t *)(state->mem + sp)) = state->reg[0];
+		state->reg[0] = *operand;
+		state->reg[1] = sp;
+		break; }
+	case 6: {
+		// RETI
+		uint16_t sp = state->reg[1];
+		state->reg[2] = *((uint16_t *)(state->mem + sp));
+		state->reg[0] = *((uint16_t *)(state->mem + sp + 2));
+		state->reg[1] = sp + 4;
+		break; }
+	default:
+		return -1;
+		break;
+	}
+
+	return 0;
+}
+
+int msp430_do_cycle_dual_operand(msp430_t *state, uint16_t opcode)
+{
+	uint16_t *src = msp430_do_cycle_get_source_operand(state, opcode);
+	uint16_t *dst = msp430_do_cycle_get_dest_operand(state, opcode);
+	if (src == 0 || dst == 0)
+		return -1;
+
+	switch ((opcode & 0xF000) >> 12) {
+	case 4:
+		// MOV
+		*dst = *src;
+		break;
+	case 5: {
+		// ADD
+		uint32_t res = *src + *dst;
+		uint16_t sr = 0;
+		if ((int16_t)res < 0)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((res & 0xFFFF0000) != 0)
+			sr |= MSP430_SR_C;
+		if (((*src & 0x8000) ^ (*src & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
+			sr |= MSP430_SR_V;
+		*dst = (uint16_t)res;
+		state->reg[2] =	sr;
+		break; }
+	case 6: {
+		// ADDC
+		uint32_t res = *src + *dst + (state->reg[2] & MSP430_SR_C);
+		uint16_t sr = 0;
+		if ((int16_t)res < 0)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((res & 0xFFFF0000) != 0)
+			sr |= MSP430_SR_C;
+		if (((*src & 0x8000) ^ (*src & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
+			sr |= MSP430_SR_V;
+		*dst = (uint16_t)res;
+		state->reg[2] =	sr;
+		break; }
+	case 7: {
+		// SUBC
+		uint32_t res = *dst + ~(*src) + (state->reg[2] & MSP430_SR_C);
+		uint16_t sr = 0;
+		if ((int16_t)res < 0)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((res & 0xFFFF0000) != 0)
+			sr |= MSP430_SR_C;
+		if (((*src & 0x8000) ^ (*src & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
+			sr |= MSP430_SR_V;
+		*dst = (uint16_t)res;
+		state->reg[2] =	sr;
+		break; }
+	case 8: {
+		// SUB
+		uint32_t res = *dst + ~(*src) + 1;
+		uint16_t sr = 0;
+		if ((int16_t)res < 0)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((res & 0xFFFF0000) != 0) // TODO confirm
+			sr |= MSP430_SR_C;
+		if (((*src & 0x8000) ^ (*src & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
+			sr |= MSP430_SR_V;
+		*dst = (uint16_t)res;
+		state->reg[2] =	sr;
+		break; }
+	case 9: {
+		// CMP
+		uint32_t res = *dst + ~(*src) + 1;
+		uint16_t sr = 0;
+		if ((int16_t)res < 0)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if ((res & 0xFFFF0000) != 0)
+			sr |= MSP430_SR_C;
+		if (((*src & 0x8000) ^ (*src & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
+			sr |= MSP430_SR_V;
+		state->reg[2] =	sr;
+		break; }
+	case 10:
+		// DADD TODO
+		break;
+	case 11: {
+		// BIT
+		uint16_t res = *dst & *src;
+		uint16_t sr = 0;
+		if (res & 0x8000)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if (res != 0)
+			sr |= MSP430_SR_C;
+		state->reg[2] =	sr;
+		break; }
+	case 12:
+		// BIC
+		*dst &= ~(*src);
+		break;
+	case 13:
+		// BIS
+		*dst |= *src;
+		break;
+	case 14: {
+		// XOR
+		uint16_t res = *dst ^ *src;
+		uint16_t sr = 0;
+		if (res & 0x8000)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if (res != 0)
+			sr |= MSP430_SR_C;
+		if ((*dst & 0x8000) && (*src & 0x8000))
+			sr |= MSP430_SR_V;
+		*dst = res;
+		state->reg[2] =	sr;
+		break; }
+	case 15: {
+		// AND
+		uint16_t res = *dst & *src;
+		uint16_t sr = 0;
+		if (res & 0x8000)
+			sr |= MSP430_SR_N;
+		if (res == 0)
+			sr |= MSP430_SR_Z;
+		if (res != 0)
+			sr |= MSP430_SR_C;
+		*dst = res;
+		state->reg[2] =	sr;
+		break; }
+	default:
+		return -1;
+	}
+
+	return 0;
+}
+
diff --git a/tests/Makefile b/tests/Makefile
new file mode 100644
index 0000000..43d4134
--- /dev/null
+++ b/tests/Makefile
@@ -0,0 +1,24 @@
+DEBUG := #-DDEBUG
+
+LIB430COREDIR = ..
+
+TEST_CSRC = test.c
+TEST_OUT = $(patsubst %.c,%.o,$(TEST_CSRC))
+
+all: $(LIB430COREDIR)/lib430core.a $(TEST_OUT)
+
+$(LIB430COREDIR)/lib430core.a:
+	@$(MAKE) -C ..
+
+.c.o:
+	@echo "Testing" $< "..."
+	@msp430-elf32-gcc -T../link.ld $< -o tmp.elf -nostdlib -lgcc -lc
+	@msp430-elf32-objcopy -Obinary tmp.elf tmp.bin
+	@echo "#define TESTBIN \\" > test.h
+	@od -t x1 tmp.bin | awk '{for (i=2; i<=NF; i++) printf "0x" $$i ", "}' >> test.h
+	@printf "\n#define TESTSIZE %u \n" $$(msp430-elf32-objdump tmp.elf -Dj .text | grep -E "^\s+[0-9a-fA-F]+:" | wc -l) >> test.h
+	@echo >> test.h
+	@gcc -Os -ggdb -g3 -Wall -W -pedantic $(DEBUG) -I../src -o tmp \
+		core_test.c -L$(LIB430COREDIR) -l430core
+	@./tmp > log
+	@rm log tmp.elf tmp.bin tmp test.h
diff --git a/tests/core_test.c b/tests/core_test.c
new file mode 100644
index 0000000..08e2650
--- /dev/null
+++ b/tests/core_test.c
@@ -0,0 +1,52 @@
+#include "core.h"
+#include "test.h"
+
+#include <stdio.h>
+
+//#define DEBUG
+
+#ifdef DEBUG
+static void dump_state(msp430_t *state)
+{
+	puts("MSP430 dump state:");
+	printf("R0/PC: 0x%04x R1/SP: 0x%04x R2/SR: 0x%04x R3:  0x%04x\n",
+		state->reg[0], state->reg[1], state->reg[2], state->reg[3]);
+	printf("R4:    0x%04x R5:    0x%04x R6:    0x%04x R7:  0x%04x\n",
+		state->reg[4], state->reg[5], state->reg[6], state->reg[7]);
+	printf("R8:    0x%04x R9:    0x%04x R10:   0x%04x R11: 0x%04x\n",
+		state->reg[8], state->reg[9], state->reg[10], state->reg[11]);
+	printf("R12:   0x%04x R13:   0x%04x R14:   0x%04x R15: 0x%04x\n\n",
+		state->reg[12], state->reg[13], state->reg[14], state->reg[15]);
+}
+#endif // DEBUG
+
+static uint8_t mem[0x10000] = {
+	TESTBIN
+};
+
+int main()
+{
+	msp430_t state;
+
+	msp430_init_state(&state, mem);
+
+#ifdef DEBUG
+	dump_state(&state);
+#endif // DEBUG
+	int r;
+	do {
+		r = msp430_do_cycle(&state);
+		if (r < 0) {
+			printf("Failed to execute near PC=0x%04x!\n", state.reg[0]);
+			return 1;
+			//break;
+		}
+
+#ifdef DEBUG
+		dump_state(&state);
+#endif // DEBUG
+	} while (r != 1);
+
+	return 0;
+}
+
diff --git a/tests/test.c b/tests/test.c
new file mode 100644
index 0000000..8eb344a
--- /dev/null
+++ b/tests/test.c
@@ -0,0 +1,8 @@
+int main()
+{
+	volatile int *mem = (int *)0x200;
+	*mem = 24;
+	for (int i = 0; i < 8; ++i)
+		*mem += 2;
+	return *mem;
+}