initial import

tests/asicworld/code_hdl_models_lfsr_updown.v

@@ -0,0 +1,35 @@
+`define WIDTH 8 
+module lfsr_updown (
+clk       ,   // Clock input
+reset     ,   // Reset input
+enable    ,   // Enable input
+up_down   ,   // Up Down input
+count     ,   // Count output
+overflow      // Overflow output
+);
+
+ input clk;
+ input reset;
+ input enable; 
+ input up_down;
+
+ output [`WIDTH-1 : 0] count;
+ output overflow;
+
+ reg [`WIDTH-1 : 0] count;
+
+ assign overflow = (up_down) ? (count == {{`WIDTH-1{1'b0}}, 1'b1}) : 
+                               (count == {1'b1, {`WIDTH-1{1'b0}}}) ;
+
+ always @(posedge clk)
+ if (reset) 
+    count <= {`WIDTH{1'b0}};
+ else if (enable) begin
+    if (up_down) begin
+      count <= {~(^(count & `WIDTH'b01100011)),count[`WIDTH-1:1]};
+    end else begin
+      count <= {count[`WIDTH-2:0],~(^(count &  `WIDTH'b10110001))};
+    end
+ end
+
+endmodule