/********************************************************************** * unique case statements with incomplete case items (run-time error) * * Author: Stuart Sutherland * * (c) Copyright 2003, Sutherland HDL, Inc. *** ALL RIGHTS RESERVED *** * www.sutherland-hdl.com * * Used with permission in the book, "SystemVerilog for Design" *  By Stuart Sutherland, Simon Davidmann, and Peter Flake. *  Book copyright: 2003, Kluwer Academic Publishers, Norwell, MA, USA *  www.wkap.il, ISBN: 0-4020-7530-8 * * Revision History: *   1.00 15 Dec 2003 -- original code, as included in book *   1.01 10 Jul 2004 -- cleaned up comments, added expected results *                       to output messages * * Caveat: Expected results displayed for this code example are based * on an interpretation of the SystemVerilog 3.1 standard by the code * author or authors.  At the time of writing, official SystemVerilog * validation suites were not available to validate the example. * * RIGHT TO USE: This code example, or any portion thereof, may be * used and distributed without restriction, provided that this entire * comment block is included with the example. * * DISCLAIMER: THIS CODE EXAMPLE IS PROVIDED "AS IS" WITHOUT WARRANTY * OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED * TO WARRANTIES OF MERCHANTABILITY, FITNESS OR CORRECTNESS. IN NO * EVENT SHALL THE AUTHOR OR AUTHORS BE LIABLE FOR ANY DAMAGES, * INCLUDING INCIDENTAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF THE * USE OF THIS CODE. *********************************************************************/module chip (output logic [15:0] y,             input        [15:0] a, b,             input        [ 2:0] opcode);  always_comb    unique case (opcode)      3'b000:   y = a + b;      3'b001:   y = a - b;      3'b010:   y = a * b;      3'b100:   y = a / b;    endcaseendmodulemodule test;  bit   [ 2:0] opcode;  logic [15:0] a, b;  wire  [15:0] y;  chip chip (y, a, b, opcode);  initial begin    $display("\nSetting different values of opcode: ");    $display("expect run-time warnings for values of 011 and 101 (binary)");    $monitor("  opcode=%b  a=%0d  b=%0d  y=%0d", opcode, a, b, y);    a = 5; b = 2;    #1 opcode = 3'b001;    #1 opcode = 3'b011;    #1 opcode = 3'b101;    #1 $display("");    $finish;  endendmodule