corelogic: round-robin module

migen/corelogic/roundrobin.py

@@ -0,0 +1,22 @@
+from migen.fhdl import structure as f
+
+class Inst:
+	def __init__(self, n):
+		self.n = n
+		self.bn = f.BitsFor(self.n-1)
+		f.Declare(self, "request", f.BV(self.n))
+		f.Declare(self, "grant", f.BV(self.bn))
+	
+	def GetFragment(self):
+		cases = []
+		for i in range(self.n):
+			switch = []
+			for j in reversed(range(i+1,i+self.n)):
+				t = j % self.n
+				switch = [f.If(self.request[t],
+					[f.Assign(self.grant, f.Constant(t, f.BV(self.bn)))],
+					switch)]
+			case = f.If(~self.request[i], switch)
+			cases.append((f.Constant(i, f.BV(self.bn)), case))
+		statement = f.Case(self.grant, cases)
+		return f.Fragment(sync=[statement])