minor update

hw/rtl/libs/VX_shift_register.v

@@ -0,0 +1,50 @@
+`include "VX_define.vh"
+
+module VX_shift_register #( 
+    parameter DATAW = 1, 
+    parameter DEPTH = 0
+) (
+    input wire              clk,
+    input wire              reset,
+    input wire              enable,
+    input wire [DATAW-1:0]  in,
+    output wire [DATAW-1:0] out
+);
+    if (0 == DEPTH) begin
+
+        assign out = in;
+
+    end if (1 == DEPTH) begin
+
+        reg [DATAW-1:0] ram;
+
+        always @(posedge clk) begin
+            if (reset) begin
+                ram <= '0;
+            end else begin
+                if (enable) begin                    
+                    ram <= in;
+                end
+            end
+        end
+
+        assign out = ram;
+
+    end else begin        
+        
+        reg [DEPTH-1:0][DATAW-1:0] ram;
+        
+        always @(posedge clk) begin
+            if (reset) begin
+                ram <= '0;
+            end else begin
+                if (enable) begin                    
+                    ram <= {ram[DEPTH-2:0], in};
+                end
+            end
+        end
+
+        assign out = ram [DEPTH-1];
+    end    
+
+endmodule