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Correctly handle resets in AsyncFIFO.

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This commit improves handling of resets in AsyncFIFO in two ways:
  * First, resets no longer violate Gray counter CDC invariants.
  * Second, write domain reset now empties the entire FIFO.
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awygle 2020-03-14 16:26:07 -07:00 • committed by GitHub
parent 12c79025f3
commit 4601dd0a69
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3 changed files with 41 additions and 5 deletions
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3
nmigen/test/test_lib_fifo.py
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@ -220,6 +220,9 @@ class FIFOContractSpec(Elaboratable):
with m.If(Past(Initial(), self.bound - 1)):
m.d.comb += Assert(read_fsm.ongoing("DONE"))
with m.If(ResetSignal(domain=self.w_domain)):
m.d.comb += Assert(~fifo.r_rdy)
if self.w_domain != "sync" or self.r_domain != "sync":
m.d.comb += Assume(Rose(ClockSignal(self.w_domain)) |
Rose(ClockSignal(self.r_domain)))