ma = Signal()
mb = Signal()

def process_a():
  v = 0
  while True:
    yield Tick("a")
    v = 1-v
    yield ma.eq(v)

def process_b():
  v = 0
  while True:
    yield Tick("b")
    v = 1-v
    yield mb.eq(v)

def test():
  while True:
    yield Tick("a")
    print(yield ma)
    print(yield mb)
    yield Tick("b")
    print(yield ma)
    print(yield mb)