cdc: reset GrayCounter gray output early

* this is not a binary-to-gray encoder, i.e. no pipeline * binary and gray would otherwise be out-of-sync for one cycle, even and especially in the same clock domain * appears to be standard practice to ensure their synchronization (http://www.sunburst-design.com/papers/CummingsSNUG2008Boston_CDC.pdf) * causes problems in artiq
m-labs · Jun 30, 2017 · 68c1af4 · 68c1af4
1 parent 991edb6
commit 68c1af4
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/migen/genlib/cdc.py b/migen/genlib/cdc.py
@@ -120,7 +120,7 @@ def __init__(self, width, idomain, odomain, timeout=128):
 class GrayCounter(Module):
     def __init__(self, width):
         self.ce = Signal()
-        self.q = Signal(width, reset_less=True)
+        self.q = Signal(width)
         self.q_next = Signal(width)
         self.q_binary = Signal(width)
         self.q_next_binary = Signal(width)