litex/examples/basic/fsm.py

from migen.fhdl.std import *
from migen.fhdl import verilog
from migen.genlib.fsm import FSM, NextState, NextValue

class Example(Module):
	def __init__(self):
		self.s = Signal()
		self.counter = Signal(8)

		myfsm = FSM()
		self.submodules += myfsm

		myfsm.act("FOO",
			self.s.eq(1),
			NextState("BAR")
		)
		myfsm.act("BAR",
			self.s.eq(0),
			NextValue(self.counter, self.counter + 1),
			NextState("FOO")
		)

		self.be = myfsm.before_entering("FOO")
		self.ae = myfsm.after_entering("FOO")
		self.bl = myfsm.before_leaving("FOO")
		self.al = myfsm.after_leaving("FOO")

example = Example()
print(verilog.convert(example, {example.s, example.counter, example.be, example.ae, example.bl, example.al}))