Adding a generic ring oscillator

lambdalib/analoglib/__init__.py

@@ -1,3 +1,6 @@
 from .la_pll.la_pll import PLL
+from .la_ring.la_ring import Ring
 
-__all__ = ['PLL']
+__all__ = ['PLL',
+           'Ring'
+           ]

lambdalib/analoglib/la_ring/la_ring.py

@@ -0,0 +1,17 @@
+from lambdalib.lambdalib import Lambda
+from lambdalib.stdlib import Inv
+from lambdalib.stdlib import Nand2
+
+class Ring(Lambda):
+    def __init__(self):
+        name = 'la_ring'
+        super().__init__(name, __file__)
+
+        # deps
+        self.add_depfileset(Inv(), depfileset='rtl', fileset='rtl')
+        self.add_depfileset(Nand2(), depfileset='rtl', fileset='rtl')
+
+
+if __name__ == "__main__":
+    d = Ring()
+    d.write_fileset(f"{d.name}.f", fileset="rtl")

lambdalib/analoglib/la_ring/rtl/la_ring.v

@@ -0,0 +1,37 @@
+/**************************************************************************
+ * Function: Generic Ring Oscillator
+ * Copyright: Lambda Project Authors. All rights Reserved.
+ * License:  MIT (see LICENSE file in Lambda repository)
+ *************************************************************************/
+module la_ring  #(parameter PROP = "", // cell property (vt, strength, ..)
+                  parameter N = 7      // number of stages (must be odd #)
+                  )
+   (
+    input  en,
+    output out
+    );
+
+   wire [N-1:0] stage;
+
+   genvar       i;
+   generate
+      for (i = 0; i < N; i = i + 1) begin : gen_stages
+         if (i == 0)
+           la_nand2 #(.PROP(PROP)) i0 (.a(stage[N-1]), .b(en), .z(stage[i]));
+         else
+           la_inv #(.PROP(PROP)) i0 (.a(stage[i-1]), .z(stage[i]));
+      end
+   endgenerate
+
+   assign out = stage[N-1];
+
+   // ERROR CHECKING
+   initial begin
+      if (N % 2 == 0) begin
+         $display("ERROR: Ring oscillator stages set to %0d. Must be odd for oscillation.", N);
+         $finish;
+      end
+    end
+
+
+endmodule