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lib.cdc: avoid modifying synchronizers in their elaborate() method.

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This commit is contained in:
whitequark 2019-09-23 16:42:44 +00:00
parent 51f03bb509
commit 86f0f12b58
3 changed files with 34 additions and 22 deletions
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24
nmigen/lib/cdc.py
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@ -57,19 +57,22 @@ class FFSynchronizer(Elaboratable):
self.i = i
self.o = o
self._o_domain = o_domain
self._stages = [Signal(self.i.shape(), name="stage{}".format(index),
reset=reset, reset_less=reset_less)
for index in range(stages)]
self._reset = reset
self._reset_less = reset_less
self._o_domain = o_domain
self._stages = stages
def elaborate(self, platform):
if hasattr(platform, "get_ff_sync"):
return platform.get_ff_sync(self)
m = Module()
for i, o in zip((self.i, *self._stages), self._stages):
flops = [Signal(self.i.shape(), name="stage{}".format(index),
reset=self._reset, reset_less=self._reset_less)
for index in range(self._stages)]
for i, o in zip((self.i, *flops), flops):
m.d[self._o_domain] += o.eq(i)
m.d.comb += self.o.eq(self._stages[-1])
m.d.comb += self.o.eq(flops[-1])
return m
@ -82,8 +85,7 @@ class ResetSynchronizer(Elaboratable):
self.arst = arst
self._domain = domain
self._stages = [Signal(1, name="stage{}".format(i), reset=1)
for i in range(stages)]
self._stages = stages
def elaborate(self, platform):
if hasattr(platform, "get_reset_sync"):
@ -91,11 +93,13 @@ class ResetSynchronizer(Elaboratable):
m = Module()
m.domains += ClockDomain("reset_sync", async_reset=True, local=True)
for i, o in zip((0, *self._stages), self._stages):
flops = [Signal(1, name="stage{}".format(index), reset=1)
for index in range(self._stages)]
for i, o in zip((0, *flops), flops):
m.d.reset_sync += o.eq(i)
m.d.comb += [
ClockSignal("reset_sync").eq(ClockSignal(self._domain)),
ResetSignal("reset_sync").eq(self.arst),
ResetSignal(self._domain).eq(self._stages[-1])
ResetSignal(self._domain).eq(flops[-1])
]
return m