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diff --git a/src/tb/tb_toggle.v b/src/tb/tb_toggle.v
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+//======================================================================
+//
+// tb_toggle
+// ---------
+// Testbench for the gpio pin toggler.
+//
+//
+// Author: Joachim Strombergson
+// Copyright (c) 2018, NORDUnet A/S
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+// - Redistributions of source code must retain the above copyright notice,
+//   this list of conditions and the following disclaimer.
+//
+// - Redistributions in binary form must reproduce the above copyright
+//   notice, this list of conditions and the following disclaimer in the
+//   documentation and/or other materials provided with the distribution.
+//
+// - Neither the name of the NORDUnet nor the names of its contributors may
+//   be used to endorse or promote products derived from this software
+//   without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+//======================================================================
+
+module tb_toggle();
+
+  parameter CLK_HALF_PERIOD = 1;
+  parameter CLK_PERIOD      = 2 * CLK_HALF_PERIOD;
+
+  reg tb_sys_clk;
+  reg tb_reset_n;
+  wire [7 : 0] tb_gpio_b;
+  reg [31 : 0]  cycle_ctr;
+
+  toggle dut(
+           .sys_clk(tb_sys_clk),
+           .reset_n(tb_reset_n),
+           .gpio_b(tb_gpio_b)
+          );
+
+
+  //----------------------------------------------------------------
+  // clk_gen
+  //
+  // Always running clock generator process.
+  //----------------------------------------------------------------
+  always
+    begin : clk_gen
+      #CLK_HALF_PERIOD;
+      tb_sys_clk = !tb_sys_clk;
+    end // clk_gen
+
+
+  //----------------------------------------------------------------
+  // sys_monitor()
+  //
+  // An always running process that creates a cycle counter and
+  // conditionally displays information about the DUT.
+  //----------------------------------------------------------------
+  always
+    begin : sys_monitor
+      cycle_ctr = cycle_ctr + 1;
+
+      #(CLK_PERIOD);
+
+      $display("cycle: 0x%016x gpio_b: 0x%08x  toggle_ctr: 0x%08x  toggle_reg: 0x%01x",
+               cycle_ctr, tb_gpio_b, dut.toggle_ctr_reg, dut.toggle_reg);
+    end
+
+
+  //----------------------------------------------------------------
+  // init_sim()
+  //
+  // Initialize all counters and testbed functionality as well
+  // as setting the DUT inputs to defined values.
+  //----------------------------------------------------------------
+  initial
+    begin
+      cycle_ctr     = 0;
+      tb_sys_clk    = 0;
+      tb_reset_n    = 0;
+
+      #(CLK_PERIOD * 10);
+
+      tb_reset_n    = 1;
+
+      #(CLK_PERIOD * 10000);
+      $finish;
+    end
+
+endmodule // tb_toggle
+
+//======================================================================
+// EOF tb_toggle.v
+//======================================================================