rtl: add gen_dff.v

Signed-off-by: liangkangnan <liangkangnan@163.com>

rtl/utils/gen_dff.v

@@ -0,0 +1,43 @@
+ /*                                                                      
+ Copyright 2020 Blue Liang, liangkangnan@163.com
+                                                                         
+ Licensed under the Apache License, Version 2.0 (the "License");         
+ you may not use this file except in compliance with the License.        
+ You may obtain a copy of the License at                                 
+                                                                         
+     http://www.apache.org/licenses/LICENSE-2.0                          
+                                                                         
+ Unless required by applicable law or agreed to in writing, software    
+ 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 gen_pipe_dff #(
+    parameter DW = 32)(
+
+    input wire clk,
+    input wire rst,
+    input wire hold_en,
+
+    input wire[DW-1:0] def_val,
+    input wire[DW-1:0] din,
+    output wire[DW-1:0] qout
+
+    );
+
+    reg[DW-1:0] qout_r;
+
+    always @ (posedge clk) begin
+        if (!rst | hold_en) begin
+            qout_r <= def_val;
+        end else begin
+            qout_r <= din;
+        end
+    end
+
+    assign qout = qout_r;
+
+endmodule