cordic: make interior registers reset_less

* the understanding is that the CORDIC does not hold a state that should or could be reset. the internal registers are all fully defined by the inputs and will be reset (with the pipeline delay) by resetting the inputs. * the stage counter in the iterative implementation retains its reset * significantly reduces reset congestion due to reset net in big designs
m-labs · Jun 28, 2017 · 1d3fbc4 · 1d3fbc4
1 parent 58666ae
commit 1d3fbc4
Showing 1 changed file with 8 additions and 5 deletions.
diff --git a/misoc/cores/cordic.py b/misoc/cores/cordic.py
@@ -209,9 +209,12 @@ def __init__(self, width=16, widthz=None, stages=None, guard=0,
                 self.latency = 0
 
         # inter-stage signals
-        x = [Signal((width + guard, True)) for i in range(num_sig)]
-        y = [Signal((width + guard, True)) for i in range(num_sig)]
-        z = [Signal((widthz + guard, True)) for i in range(num_sig)]
+        x = [Signal((width + guard, True), reset_less=True)
+                for i in range(num_sig)]
+        y = [Signal((width + guard, True), reset_less=True)
+                for i in range(num_sig)]
+        z = [Signal((widthz + guard, True), reset_less=True)
+                for i in range(num_sig)]
 
         # hook up inputs and outputs to the first and last inter-stage
         # signals
@@ -231,12 +234,12 @@ def __init__(self, width=16, widthz=None, stages=None, guard=0,
                 self.new_in.eq(i == stages),
                 self.new_out.eq(i == 1),
             ]
-            ai = Signal((widthz + guard, True))
+            ai = Signal((widthz + guard, True), reset_less=True)
             self.sync += ai.eq(Array(a)[i])
             if range(stages) == s:
                 si = i - 1  # shortcut if no stage repetitions
             else:
-                si = Signal(max=stages + 1)
+                si = Signal(max=stages + 1, reset_less=True)
                 self.sync += si.eq(Array(s)[i])
             xi, yi, zi = x[1], y[1], z[1]
             self.sync += [