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lib.fifo.AsyncFFSynchronizer: check input and output signal width #517

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merged 1 commit into from
Oct 28, 2020
Merged

lib.fifo.AsyncFFSynchronizer: check input and output signal width #517

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16 changes: 12 additions & 4 deletions nmigen/lib/cdc.py
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Original file line number Diff line number Diff line change
Expand Up @@ -128,16 +128,24 @@ class AsyncFFSynchronizer(Elaboratable):
def __init__(self, i, o, *, o_domain="sync", stages=2, async_edge="pos", max_input_delay=None):
_check_stages(stages)

if len(i) != 1:
raise ValueError("AsyncFFSynchronizer input width must be 1, not {}"
.format(len(i)))
if len(o) != 1:
raise ValueError("AsyncFFSynchronizer output width must be 1, not {}"
.format(len(o)))

if async_edge not in ("pos", "neg"):
raise ValueError("AsyncFFSynchronizer async edge must be one of 'pos' or 'neg', "
"not {!r}"
.format(async_edge))

self.i = i
self.o = o

self._o_domain = o_domain
self._stages = stages

if async_edge not in ("pos", "neg"):
raise ValueError("AsyncFFSynchronizer async edge must be one of 'pos' or 'neg', "
"not {!r}"
.format(async_edge))
self._edge = async_edge

self._max_input_delay = max_input_delay
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8 changes: 8 additions & 0 deletions tests/test_lib_cdc.py
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,14 @@ def test_edge_wrong(self):
r"^AsyncFFSynchronizer async edge must be one of 'pos' or 'neg', not 'xxx'$"):
AsyncFFSynchronizer(Signal(), Signal(), o_domain="sync", async_edge="xxx")

def test_width_wrong(self):
with self.assertRaisesRegex(ValueError,
r"^AsyncFFSynchronizer input width must be 1, not 2$"):
AsyncFFSynchronizer(Signal(2), Signal(), o_domain="sync")
with self.assertRaisesRegex(ValueError,
r"^AsyncFFSynchronizer output width must be 1, not 2$"):
AsyncFFSynchronizer(Signal(), Signal(2), o_domain="sync")

def test_pos_edge(self):
i = Signal()
o = Signal()
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