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lib.fifo.AsyncFIFOBuffered: fix FFSynchronizer latency

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Robin Ole Heinemann 2021-01-03 00:14:26 +01:00 committed by whitequark
parent d15705cf4f
commit 2a7a3aef87
2 changed files with 5 additions and 1 deletions
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2
nmigen/lib/fifo.py
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@ -513,7 +513,7 @@ class AsyncFIFOBuffered(Elaboratable, FIFOInterface):
m.d[self._r_domain] += self.r_level.eq(fifo.r_level + r_consume_buffered)
w_consume_buffered = Signal()
m.submodules.consume_buffered_cdc = FFSynchronizer(r_consume_buffered, w_consume_buffered, o_domain=self._w_domain)
m.submodules.consume_buffered_cdc = FFSynchronizer(r_consume_buffered, w_consume_buffered, o_domain=self._w_domain, stages=4)
m.d.comb += self.w_level.eq(fifo.w_level + w_consume_buffered)
with m.If(self.r_en | ~self.r_rdy):

4
tests/test_lib_fifo.py
View file

@ -344,6 +344,10 @@ class AsyncFIFOSimCase(FHDLTestCase):
fifo = AsyncFIFOBuffered(width=32, depth=9, r_domain="read", w_domain="write")
self.check_async_fifo_level(fifo, fill_in=5, expected_level=5)
def test_async_buffered_fifo_level_only_three(self):
fifo = AsyncFIFOBuffered(width=32, depth=9, r_domain="read", w_domain="write")
self.check_async_fifo_level(fifo, fill_in=3, expected_level=3)
def test_async_buffered_fifo_level_full(self):
fifo = AsyncFIFOBuffered(width=32, depth=9, r_domain="read", w_domain="write")
self.check_async_fifo_level(fifo, fill_in=10, expected_level=9)