class Sweep:
def __init__(self):
self.is_enabled = False
self.reload = False
self.divider = Divider()
self.negative_flag = False
self.shift = 0
def reset(self):
self.is_enabled = False
self.reload = False
self.divider = Divider()
def step(self):
"""Returns true if pulse period needs to be adjusted"""
return_value = False
if self.reload:
if self.divider.counter == 0 and self.is_enabled:
return_value = True
self.divider.reload()
self.reload = False # Done reloading
elif self.divider.step() and self.is_enabled:
self.divider.reload()
return_value = True
return return_value
class Envelope:
def __init__(self):
self.start = False
self.loop = False
self.divider = Divider()
self.counter = 0x00 # 1 byte
def reset(self):
self.start = False
self.loop = False
self.divider.reset()
self.counter = 0x00
def step(self):
if self.start:
self.start = False
self.counter = 0x0F
self.divider.reload()
elif self.divider.step():
if self.counter > 0:
self.counter = (self.counter - 1) & 0xFF
elif self.loop:
self.counter = 0x0F
class Noise:
LENGTH_COUNTER_DATA = [
10, 254, 20, 2, 40, 4, 80, 6, 160, 8, 60, 10, 14, 12, 26, 14, 12, 16,
24, 18, 48, 20, 96, 22, 192, 24, 72, 26, 16, 28, 32, 30
]
PERIOD_DATA = [
4,
8,
16,
32,
64,
96,
128,
160,
202,
254,
380,
508,
762,
1016,
2034,
4068,
]
def __init__(self):
self.envelope = Envelope()
self.divider = Divider()
self.shift = 0x0000
self.length_counter = 0x00
self.is_enabled = False
self.registers = [0x00, 0x00, 0x00]
def reset(self):
self.is_enabled = False
self.registers = [0x00, 0x00, 0x00]
self.divider.reset()
self.length_counter = 0x00
self.envelope.reset()
self.shift = 0x0000
def enable(self):
self.is_enabled = True
def disable(self):
self.is_enabled = False
self.length_counter = 0x00
def read_register(self, address):
if address == 0x400c:
return self.registers[0]
elif address == 0x400e:
return self.registers[1]
elif address == 0x400f:
return self.registers[2]
else:
raise NoiseError("Invalid read access to register {}".format(
hex(address)))
def write_register(self, address, value):
if address == 0x400c:
# --lc.vvvv, length counter halt, constant volume/envelope flag, volume/envelope divider period
self.registers[0] = value
self.envelope.loop = ((value >> 5) & 1) == 1
self.envelope.divider.period = value & 0x0F
elif address == 0x400e:
# M---.PPPP Mode, period
self.registers[1] = value
self.divider.period = self.PERIOD_DATA[value & 0x0F]
self.divider.reload()
elif address == 0x400F:
# llll.l--- Length counter load and envelope restart
self.registers[2] = value
self.envelope.start = True
if self.is_enabled:
self.length_counter = self.LENGTH_COUNTER_DATA[value >> 3]
else:
raise NoiseError("Invalid write access to register {}".format(
hex(address)))
def output(self):
if not self.is_enabled:
return 0
if self.shift & 0x0001 != 0:
return 0
if self.length_counter == 0:
return 0
if (self.registers[0] >> 4) & 0x01: # Constant volume flag
return self.envelope.counter
else:
return self.registers[0] & 0x0F