add flopenrs back

src/generic/flop/flopenrs.sv

@@ -0,0 +1,52 @@
+///////////////////////////////////////////
+// flopenrs.sv
+//
+// Written: matthew.n.otto@okstate.edu 15 April 2024
+// Modified: 
+//
+// Purpose: Scannable D flip-flop with enable, synchronous reset
+// 
+// A component of the CORE-V-WALLY configurable RISC-V project.
+// https://github.com/openhwgroup/cvw
+// 
+// Copyright (C) 2021-24 Harvey Mudd College & Oklahoma State University
+//
+// SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1
+//
+// Licensed under the Solderpad Hardware License v 2.1 (the “License”); you may not use this file 
+// except in compliance with the License, or, at your option, the Apache License Version 2.0. You 
+// may obtain a copy of the License at
+//
+// https://solderpad.org/licenses/SHL-2.1/
+//
+// Unless required by applicable law or agreed to in writing, any work distributed under the 
+// License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
+// either express or implied. See the License for the specific language governing permissions 
+// and limitations under the License.
+////////////////////////////////////////////////////////////////////////////////////////////////
+
+module flopenrs #(parameter WIDTH = 8) (
+  input  logic clk, reset, en,
+  input  logic [WIDTH-1:0] d,
+  output logic [WIDTH-1:0] q,
+  input  logic scan, // scan enable
+  input  logic scanin,
+  output logic scanout
+);
+  logic [WIDTH-1:0] dmux;
+
+  assign dmux[WIDTH-1] = scan ? scanin : d[WIDTH-1];
+  assign scanout = q[0];
+
+  genvar i;
+  for (i=0; i<WIDTH-1; i=i+1) begin
+    assign dmux[i] = scan ? q[i+1] : d[i];
+  end
+
+  always_ff @(posedge clk)
+    if (reset)
+      q <= '0;
+    else if (en || scan)
+      q <= dmux;
+
+endmodule