22. Shared Line using wor

module alarm_siren(
  input  wire alarm1, alarm2,
  output wor  siren           // wor = wired-OR resolution
);
  // Two independent drivers onto the same 'siren' net
  assign siren = alarm1;
  assign siren = alarm2;
endmodule
💡 Remember
wor resolves multiple drivers by bitwise OR—avoids x on 0/1 conflicts.
Default wire with multiple conflicting drivers can go unknown (x), but wor defines resolution.
Net resolution behaviour is part of the standard’s wired nets semantics.

Please login to run the code.

Testbench Code

`timescale 1ns/1ps
module tb_alarm_siren;
  reg  alarm1, alarm2;
  wire siren;
  wire expected_siren;
  wire mismatch;

  alarm_siren dut(.alarm1(alarm1), .alarm2(alarm2), .siren(siren));

  assign expected_siren = alarm1 | alarm2;
  assign mismatch       = (siren !== expected_siren);

  integer TOTAL_TEST_CASES, TOTAL_PASSED_TEST_CASES, TOTAL_FAILED_TEST_CASES;
  reg [8*20-1:0] tc_name;

  initial begin
    $dumpfile("tb_alarm_siren.vcd");
    $dumpvars(0, alarm1, alarm2, siren, expected_siren, mismatch);
  end

  task run_case;
    input a1, a2;
    input [8*20-1:0] name;
    begin
      alarm1 = a1; alarm2 = a2; tc_name = name; #1;
      $display("CASE=%s : a1=%0b a2=%0b | siren=%0b expected_siren=%0b %s",
               tc_name, alarm1, alarm2, siren, expected_siren,
               mismatch ? "MISMATCH" : "OK");
      TOTAL_TEST_CASES = TOTAL_TEST_CASES + 1;
      if (!mismatch) TOTAL_PASSED_TEST_CASES = TOTAL_PASSED_TEST_CASES + 1;
      else begin
        TOTAL_FAILED_TEST_CASES = TOTAL_FAILED_TEST_CASES + 1;
        $display("  FAILED INPUTS: a1=%0b a2=%0b  EXPECTED: expected_siren=%0b",
                 alarm1, alarm2, expected_siren);
      end
      #4;
    end
  endtask

  initial begin
    TOTAL_TEST_CASES = 0; TOTAL_PASSED_TEST_CASES = 0; TOTAL_FAILED_TEST_CASES = 0;

    run_case(0,0,"both_idle");
    run_case(1,0,"alarm1_only");
    run_case(0,1,"alarm2_only");
    run_case(1,1,"both_active");

    $display("TOTAL_TEST_CASES=%0d", TOTAL_TEST_CASES);
    $display("TOTAL_PASSED_TEST_CASES=%0d", TOTAL_PASSED_TEST_CASES);
    $display("TOTAL_FAILED_TEST_CASES=%0d", TOTAL_FAILED_TEST_CASES);
    $display("ALL_TEST_CASES_PASSED=%s", (TOTAL_FAILED_TEST_CASES==0) ? "true" : "false");

    $finish;
  end
endmodule