def test_program_counter_latches():
pc = ProgramCounter()
pc.clock()
pc.clock(data=0x0D, con=['lp'])
assert pc.data(['ep']) == 0x0D
pc.clock(con=['cp'])
assert pc.data(['ep']) == 0x0E
def test_program_counter_needs_ep():
pc = ProgramCounter()
pc.clock(con=['cp'])
assert pc.data() == None
pc.reset()
assert pc.data() == None
def test_program_counter_resets():
pc = ProgramCounter()
pc.clock(con=['cp'])
assert pc.data(['ep']) == 0x01
pc.reset()
assert pc.data(['ep']) == 0x00
def test_clock_fails_if_multi_data_accessed():
# pull data from connected components from data bus
clock = Clock()
reg_a = RegisterA()
pc = ProgramCounter()
clock.add_component(reg_a)
clock.add_component(pc)
reg_a.clock(data=0xCD, con=['la'])
pc.clock(data=0xAE, con=['ep'])
control_word = ['ea', 'ep']
with pytest.raises(RuntimeError):
clock.data_bus(control_word)
def test_t0_increments_pc():
clock = Clock()
pc = ProgramCounter()
clock.add_component(pc)
# reset CPU
clock.reset()
# contrive for test
pc.clock(data=0x0C, con=['lp'])
clock.t_state = 0
# apply single clock cycle
clock.step()
assert pc.value == 0x0D
def test_t0_transfers_pc_to_mar():
clock = Clock()
pc = ProgramCounter()
mar = MemoryAddressRegister()
clock.add_component(pc)
clock.add_component(mar)
# reset CPU
clock.reset()
# contrive for test
pc.clock(data=0x0C, con=['lp'])
clock.t_state = 0
# apply single clock cycle
clock.step()
assert mar.value == 0x0C
def test_program_counter_increments():
pc = ProgramCounter()
pc.clock()
assert pc.data(['ep']) == 0x00
pc.clock(con=['cp'])
assert pc.data(['ep']) == 0x01
pc.clock(con=['cp'])
assert pc.data(['ep']) == 0x02
def test_clock_add_component():
clock = Clock()
pc = ProgramCounter()
clock.add_component(pc)