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genlib/fsm: add entering/ongoing/leaving methods

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commit 4fb3e970b130e9dad74c452d4c306fe5fdfc7e60 1 parent 9142278
@sbourdeauducq sbourdeauducq authored
Showing with 42 additions and 4 deletions.
  1. +3 −1 examples/basic/fsm.py
  2. +39 −3 migen/genlib/fsm.py
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4 examples/basic/fsm.py
@@ -9,6 +9,8 @@ def __init__(self):
self.submodules += myfsm
myfsm.act("FOO", self.s.eq(1), NextState("BAR"))
myfsm.act("BAR", self.s.eq(0), NextState("FOO"))
+ self.entering_foo = myfsm.entering("FOO")
+ self.leaving_bar = myfsm.leaving("BAR")
example = Example()
-print(verilog.convert(example, {example.s}))
+print(verilog.convert(example, {example.s, example.entering_foo, example.leaving_bar}))
View
42 migen/genlib/fsm.py
@@ -35,6 +35,9 @@ def __init__(self, reset_state=None):
self.state_aliases = dict()
self.reset_state = reset_state
+ self.entering_signals = OrderedDict()
+ self.leaving_signals = OrderedDict()
+
def act(self, state, *statements):
if self.finalized:
raise FinalizeError
@@ -56,14 +59,37 @@ def delayed_enter(self, name, target, delay):
state = next_state
else:
self.state_aliases[name] = target
+
+ def ongoing(self, state):
+ is_ongoing = Signal()
+ self.act(state, is_ongoing.eq(1))
+ return is_ongoing
+
+ def _entering_leaving(self, d, state):
+ if state not in self.actions:
+ self.actions[state] = []
+ try:
+ return d[state]
+ except KeyError:
+ is_el = Signal()
+ d[state] = is_el
+ return is_el
+
+ def entering(self, state):
+ return self._entering_leaving(self.entering_signals, state)
+
+ def leaving(self, state):
+ return self._entering_leaving(self.leaving_signals, state)
def do_finalize(self):
nstates = len(self.actions)
+ if self.reset_state is None:
+ reset_state = next(iter(self.actions.keys()))
+ else:
+ reset_state = self.reset_state
self.encoding = dict((s, n) for n, s in enumerate(self.actions.keys()))
- self.state = Signal(max=nstates)
- if self.reset_state is not None:
- self.state.reset = self.encoding[self.reset_state]
+ self.state = Signal(max=nstates, reset=self.encoding[reset_state])
self.next_state = Signal(max=nstates)
lns = _LowerNextState(self.next_state, self.encoding, self.state_aliases)
@@ -73,3 +99,13 @@ def do_finalize(self):
Case(self.state, cases)
]
self.sync += self.state.eq(self.next_state)
+
+ # drive entering/leaving signals
+ for state, is_entering in self.entering_signals.items():
+ encoded = self.encoding[state]
+ self.sync += is_entering.eq((self.next_state == encoded) & (self.state != encoded))
+ if reset_state in self.entering_signals:
+ self.entering_signals[reset_state].reset = 1
+ for state, is_leaving in self.leaving_signals.items():
+ encoded = self.encoding[state]
+ self.sync += is_leaving.eq((self.next_state != encoded) & (self.state == encoded))
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