class Chip8:
screen: Screen
keyboard: Keyboard
sound: Sound
cpu: CPU
cycles_per_frame: int
def __init__(self, scaling_factor: int, cycles_per_frame: int,
starting_address: int):
pygame.init()
self.screen = Screen(scaling_factor)
self.keyboard = Keyboard()
self.sound = Sound()
self.cpu = CPU(self.screen, self.keyboard, starting_address)
self.cycles_per_frame = cycles_per_frame
sixty_hertz_ms = round(1000 / SIXTY_HERTZ)
pygame.time.set_timer(SIXTY_HERTZ_CLOCK, sixty_hertz_ms)
print(
f"Target CPU speed: {cycles_per_frame * SIXTY_HERTZ} instructions per second"
)
print(f"Screen scaling factor: {scaling_factor}")
def load(self, rom: bytes):
self.cpu.load(rom)
def run(self):
while True:
self._handle_events()
def _handle_events(self):
for event in pygame.event.get():
if event.type == pygame.KEYDOWN:
self.keyboard.keydown(event)
elif event.type == pygame.KEYUP:
key = self.keyboard.keyup(event)
if self.cpu.waiting_for_keypress and key is not None:
self.cpu.key_was_pressed(key)
elif event.type == SIXTY_HERTZ_CLOCK:
self.tick()
elif event.type == pygame.QUIT:
pygame.quit()
sys.exit()
def tick(self):
if self.cpu.waiting_for_keypress:
return
has_screen_changed = False
self.cpu.decrease_timers()
for _ in range(self.cycles_per_frame):
try:
self.cpu.step()
except UpdateScreen:
has_screen_changed = True
except WaitForKeypress:
break
self.sound.update(self.cpu.sound_timer)
if has_screen_changed:
self.screen.update()
class TestCPU(unittest.TestCase):
def setUp(self):
self.screen = Screen()
self.keyboard = Keyboard()
self.cpu = CPU(self.screen, self.keyboard)
def test_init(self):
self.assertEqual(cpu.MEMORY_SIZE, len(self.cpu.memory))
self.assertEqual(bytearray(cpu.font_sprites),
self.cpu.memory[0:len(cpu.font_sprites)])
self.assertEqual([], self.cpu.stack)
self.assertEqual(0x200, self.cpu.pc)
self.assertEqual(0x600,
CPU(Screen(), Keyboard(), starting_address=0x600).pc)
self.assertEqual([0x00] * 16, self.cpu.V)
self.assertEqual(0x000, self.cpu.I)
self.assertEqual(0x000, self.cpu.I)
self.assertEqual(0x00, self.cpu.delay_timer)
self.assertEqual(0x00, self.cpu.sound_timer)
self.assertEqual(0x042,
CPU(Screen(), Keyboard(), starting_address=0x042).pc)
def test_decrease_timers(self):
self.cpu.delay_timer = 0x01
self.cpu.sound_timer = 0x01
self.cpu.decrease_timers()
self.assertEqual(0x00, self.cpu.delay_timer)
self.assertEqual(0x00, self.cpu.sound_timer)
self.cpu.decrease_timers()
self.assertEqual(0x00, self.cpu.delay_timer)
self.assertEqual(0x00, self.cpu.sound_timer)
def test_CLS(self): # 00E0
for row in self.screen.buffer:
for x, _ in enumerate(row):
row[x] = True
self.cpu._CLS()
for row in self.screen.buffer:
self.assertTrue(not any(row))
def test_RET(self): # 00EE
self.cpu.stack.append(0x42)
self.cpu._RET()
self.assertEqual(0x42, self.cpu.pc)
self.assertEqual([], self.cpu.stack)
def test_JP_nnn(self): # 1nnn
self.cpu.instruction = 0x1042
self.cpu._JP_nnn()
self.assertEqual(0x42, self.cpu.pc)
def test_CALL_nnn(self): # 2nnn
self.cpu.instruction = 0x2042
self.cpu.pc = 0x1234
self.cpu._CALL_nnn()
self.assertEqual(0x42, self.cpu.pc)
self.assertEqual([0x1234], self.cpu.stack)
def test_SE_Vx_nn(self): # 3xnn
addr = self.cpu.pc
self.cpu.V[0x1] = 0x42
self.cpu.instruction = 0x3042
self.cpu._SE_Vx_nn()
self.assertEqual(addr, self.cpu.pc)
self.cpu.instruction = 0x3141
self.cpu._SE_Vx_nn()
self.assertEqual(addr, self.cpu.pc)
self.cpu.instruction = 0x3142
self.cpu._SE_Vx_nn()
self.assertEqual(addr + 2, self.cpu.pc)
def test_SNE_Vx_nn(self): # 4xnn
addr = self.cpu.pc
self.cpu.V[0x1] = 0x42
self.cpu.instruction = 0x4142
self.cpu._SNE_Vx_nn()
self.assertEqual(addr, self.cpu.pc)
self.cpu.instruction = 0x4042
self.cpu._SNE_Vx_nn()
self.assertEqual(addr + 2, self.cpu.pc)
self.cpu.instruction = 0x4141
self.cpu._SNE_Vx_nn()
self.assertEqual(addr + 4, self.cpu.pc)
def test_SE_Vx_Vy(self): # 5xy0
self.cpu.instruction = 0x5120
addr = self.cpu.pc
self.cpu.V[0x1] = 0x41
self.cpu.V[0x2] = 0x42
self.cpu._SE_Vx_Vy()
self.assertEqual(addr, self.cpu.pc)
self.cpu.V[0x1] = 0x42
self.cpu._SE_Vx_Vy()
self.assertEqual(addr + 2, self.cpu.pc)
def test_LD_Vx_nn(self): # 6xnn
self.cpu.instruction = 0x6142
self.cpu._LD_Vx_nn()
self.assertEqual(0x42, self.cpu.V[0x1])
self.cpu._LD_Vx_nn()
self.assertEqual(0x42, self.cpu.V[0x1])
def test_ADD_Vx_nn(self): # 7xnn
self.cpu.instruction = 0x7101
self.cpu.V[0x1] = 0xfe
self.cpu._ADD_Vx_nn()
self.assertEqual(0xff, self.cpu.V[0x1])
self.assertEqual(0x00, self.cpu.V[0xf])
self.cpu._ADD_Vx_nn()
self.assertEqual(0x00, self.cpu.V[0x1])
self.assertEqual(0x00, self.cpu.V[0xf])
def test_LD_Vx_Vy(self): # 8xy0
self.cpu.instruction = 0x8010
self.cpu.V[0x1] = 0x42
self.cpu._LD_Vx_Vy()
self.assertEqual(0x42, self.cpu.V[0x0])
def test_OR_Vx_Vy(self): # 8xy1
self.cpu.instruction = 0x8121
self.cpu.V[0x1] = 0b01010101
self.cpu.V[0x2] = 0b00001111
self.cpu._OR_Vx_Vy()
self.assertEqual(0b01011111, self.cpu.V[0x1])
def test_AND_Vx_Vy(self): # 8xy2
self.cpu.instruction = 0x8122
self.cpu.V[0x1] = 0b01010101
self.cpu.V[0x2] = 0b00001111
self.cpu._AND_Vx_Vy()
self.assertEqual(0b00000101, self.cpu.V[0x1])
def test_XOR_Vx_Vy(self): # 8xy3
self.cpu.instruction = 0x8123
self.cpu.V[0x1] = 0b01010101
self.cpu.V[0x2] = 0b00001111
self.cpu._XOR_Vx_Vy()
self.assertEqual(0b01011010, self.cpu.V[0x1])
def test_ADD_Vx_Vy(self): # 8xy4
self.cpu.instruction = 0x8124
self.cpu.V[0x1] = 0xfe
self.cpu.V[0x2] = 0x01
self.cpu._ADD_Vx_Vy()
self.assertEqual(0xff, self.cpu.V[0x1])
self.assertEqual(0x00, self.cpu.V[0xf])
self.cpu._ADD_Vx_Vy()
self.assertEqual(0x00, self.cpu.V[0x1])
self.assertEqual(0x01, self.cpu.V[0xf])
def test_SUB_Vx_Vy(self): # 8xy5
self.cpu.instruction = 0x8125
self.cpu.V[0x1] = 0x01
self.cpu.V[0x2] = 0x01
self.cpu._SUB_Vx_Vy()
self.assertEqual(0x00, self.cpu.V[0x1])
self.assertEqual(0x01, self.cpu.V[0xf])
self.cpu._SUB_Vx_Vy()
self.assertEqual(0xff, self.cpu.V[0x1])
self.assertEqual(0x00, self.cpu.V[0xf])
def test_SHR_Vx_Vy(self): # 8xy6
self.cpu.instruction = 0x8126
self.cpu.V[0x2] = 0b11110000
self.cpu._SHR_Vx_Vy()
self.assertEqual(0b01111000, self.cpu.V[0x1])
self.assertEqual(0b00000000, self.cpu.V[0xf])
self.cpu.V[0x2] = 0b00001111
self.cpu._SHR_Vx_Vy()
self.assertEqual(0b00000111, self.cpu.V[0x1])
self.assertEqual(0b00000001, self.cpu.V[0xf])
def test_SUBN_Vx_Vy(self): # 8xy7
self.cpu.instruction = 0x8127
self.cpu.V[0x1] = 0x01
self.cpu.V[0x2] = 0x01
self.cpu._SUBN_Vx_Vy()
self.assertEqual(0x00, self.cpu.V[0x1])
self.assertEqual(0x01, self.cpu.V[0xf])
self.cpu.V[0x1] = 0x02
self.cpu._SUBN_Vx_Vy()
self.assertEqual(0xff, self.cpu.V[0x1])
self.assertEqual(0x00, self.cpu.V[0xf])
def test_SHL_Vx_Vy(self): # 8xyE
self.cpu.instruction = 0x812E
self.cpu.V[0x2] = 0b11110000
self.cpu._SHL_Vx_Vy()
self.assertEqual(0b11100000, self.cpu.V[0x1])
self.assertEqual(0b00000001, self.cpu.V[0xf])
self.cpu.V[0x2] = 0b00001111
self.cpu._SHL_Vx_Vy()
self.assertEqual(0b00011110, self.cpu.V[0x1])
self.assertEqual(0b00000000, self.cpu.V[0xf])
def test_SNE_Vx_Vy(self): # 9xy0
self.cpu.instruction = 0x9120
addr = self.cpu.pc
self.cpu.V[0x1] = 0x42
self.cpu.V[0x2] = 0x42
self.cpu._SNE_Vx_Vy()
self.assertEqual(addr, self.cpu.pc)
self.cpu.V[0x1] = 0x41
self.cpu._SNE_Vx_Vy()
self.assertEqual(addr + 2, self.cpu.pc)
def test_LD_I_nnn(self): # Annn
self.cpu.instruction = 0xA042
self.cpu._LD_I_nnn()
self.assertEqual(0x42, self.cpu.I)
def test_JP_V0_nnn(self): # Bnnn
self.cpu.instruction = 0xB042
self.cpu.V[0x0] = 0x42
self.cpu._JP_V0_nnn()
self.assertEqual(0x42 + 0x42, self.cpu.pc)
def test_RND_Vx_nn(self): # Cxnn
numbers = set()
for mask in range(0xff + 1):
self.cpu.instruction = 0xC100 | mask
self.cpu._RND_Vx_nn()
rnd = self.cpu.V[0x1]
self.assertEqual(rnd & mask, rnd)
numbers.add(rnd)
self.assertGreater(len(numbers), 50)
def test_DRW_Vx_Vy_n(self): # Dxyn
to_int = lambda bool_list: sum(
[val << (7 - pos) for pos, val in enumerate(bool_list)])
x = 4
y = 2
digit = 7
self.cpu.instruction = 0xD125
self.cpu.I = digit * 5
self.cpu.V[0x1] = x
self.cpu.V[0x2] = y
with self.assertRaises(UpdateScreen):
self.cpu._DRW_Vx_Vy_n()
for line in range(5):
self.assertEqual(cpu.font_sprites[digit * 5 + line],
to_int(self.screen.buffer[y + line][x:x + 8]))
self.assertEqual(0x00, self.cpu.V[0xf])
with self.assertRaises(UpdateScreen):
self.cpu._DRW_Vx_Vy_n()
for line in range(5):
self.assertEqual(0x00,
to_int(self.screen.buffer[y + line][x:x + 8]))
self.assertEqual(0x01, self.cpu.V[0xf])
self.cpu.V[0x1] = 62
self.cpu.V[0x2] = 30
with self.assertRaises(UpdateScreen):
self.cpu._DRW_Vx_Vy_n()
self.assertEqual([True, True], self.screen.buffer[30][62:64])
self.assertEqual([False, False], self.screen.buffer[31][62:64])
self.assertEqual([False, False], self.screen.buffer[0][62:64])
self.assertEqual([False, True], self.screen.buffer[1][62:64])
self.assertEqual([False, True], self.screen.buffer[2][62:64])
self.assertEqual([True, True], self.screen.buffer[30][0:2])
self.assertEqual([False, True], self.screen.buffer[31][0:2])
self.assertEqual([True, False], self.screen.buffer[0][0:2])
self.assertEqual([False, False], self.screen.buffer[1][0:2])
self.assertEqual([False, False], self.screen.buffer[2][0:2])
def test_SKP_Vx(self): # Ex9E
self.cpu.instruction = 0xE19E
addr = self.cpu.pc
self.cpu.V[0x1] = 0x1
self.cpu._SKP_Vx()
self.assertEqual(addr, self.cpu.pc)
self.keyboard.pressed_keys.add(0x1)
self.cpu._SKP_Vx()
self.assertEqual(addr + 2, self.cpu.pc)
def test_SKNP_Vx(self): # ExA1
self.cpu.instruction = 0xE1A1
addr = self.cpu.pc
self.cpu.V[0x1] = 0x1
self.keyboard.pressed_keys.add(0x1)
self.cpu._SKNP_Vx()
self.assertEqual(addr, self.cpu.pc)
self.keyboard.pressed_keys.remove(0x1)
self.cpu._SKNP_Vx()
self.assertEqual(addr + 2, self.cpu.pc)
def test_LD_Vx_DT(self): # Fx07
self.cpu.instruction = 0xF107
self.cpu.delay_timer = 0x42
self.cpu._LD_Vx_DT()
self.assertEqual(0x42, self.cpu.V[0x1])
def test_LD_Vx_K(self): # Fx0A
self.cpu.instruction = 0xF10A
with self.assertRaises(WaitForKeypress):
self.cpu._LD_Vx_K()
self.assertTrue(self.cpu.waiting_for_keypress)
self.cpu.key_was_pressed(0x1)
self.assertFalse(self.cpu.waiting_for_keypress)
self.assertEqual(0x1, self.cpu.V[0x1])
def test_LD_DT_Vx(self): # Fx15
self.cpu.instruction = 0xF115
self.cpu.V[0x1] = 0x42
self.cpu._LD_DT_Vx()
self.assertEqual(0x42, self.cpu.delay_timer)
def test_LD_ST_Vx(self): # Fx18
self.cpu.instruction = 0xF118
self.cpu.V[0x1] = 0x42
self.cpu._LD_ST_Vx()
self.assertEqual(0x42, self.cpu.sound_timer)
def test_ADD_I_Vx(self): # Fx1E
self.cpu.instruction = 0xF11E
self.cpu.V[0x1] = 0x1
self.cpu.I = 0xffe
self.cpu._ADD_I_Vx()
self.assertEqual(0xfff, self.cpu.I)
self.cpu._ADD_I_Vx()
self.assertEqual(0x000, self.cpu.I)
def test_LD_F_Vx(self): # Fx29
self.cpu.instruction = 0xF129
self.cpu.V[0x1] = 7
self.cpu._LD_F_Vx()
self.assertEqual(7 * 5, self.cpu.I)
def test_LD_B_Vx(self): # Fx33
self.cpu.instruction = 0xF133
self.cpu._LD_B_Vx()
def test_LD_I_Vx(self): # Fx55
self.cpu.instruction = 0xF755
self.cpu.I = 0x123
for reg in range(0x7 + 1):
self.cpu.V[reg] = reg * 2
self.cpu._LD_I_Vx()
for reg in range(0x7 + 1):
self.assertEqual(reg * 2, self.cpu.memory[0x123 + reg])
self.assertEqual(0x123 + 0x7 + 1, self.cpu.I)
def test_LD_Vx_I(self): # Fx65
self.cpu.instruction = 0xF765
self.cpu.I = 0x123
for reg in range(0x7 + 1):
self.cpu.memory[0x123 + reg] = reg * 2
self.cpu._LD_Vx_I()
for reg in range(0x7 + 1):
self.assertEqual(reg * 2, self.cpu.V[reg])
self.assertEqual(0x123 + 0x7 + 1, self.cpu.I)