From 478179fd21ec7147208f071260b887e866b3a5c9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Joachim=20Stro=CC=88mbergson?= <joachim@secworks.se>
Date: Thu, 14 Jun 2018 13:42:19 +0200
Subject: Adding toggle design including testbench and Makefile to run
 simulation.

---
 src/rtl/toggle.v | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 src/rtl/toggle.v

(limited to 'src/rtl/toggle.v')

diff --git a/src/rtl/toggle.v b/src/rtl/toggle.v
new file mode 100644
index 0000000..548b85e
--- /dev/null
+++ b/src/rtl/toggle.v
@@ -0,0 +1,92 @@
+//======================================================================
+//
+// toggle
+// ------
+// 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 toggle
+
+  (
+   input wire          sys_clk,
+   input wire          reset_n,
+   output wire [7 : 0] gpio_b
+  );
+
+  localparam TOGGLE_DELAY_CYCLES = 100;
+
+  reg [7 : 0] toggle_ctr_reg;
+  reg [7 : 0] toggle_ctr_new;
+
+  reg toggle_reg;
+  reg toggle_we;
+
+  assign gpio_b = {7'b1010101, toggle_reg};
+
+  always @(posedge sys_clk)
+    begin: sys_clk_toggle_reg_update
+      if (!reset_n)
+        begin
+          toggle_ctr_reg <= 32'h0;
+          toggle_reg     <= 1'b0;
+        end
+      else
+        begin
+          toggle_ctr_reg <= toggle_ctr_new;
+
+          if (toggle_we)
+            toggle_reg <= ~toggle_reg;
+        end
+    end
+
+  always @*
+    begin : sys_clk_toggle
+      if (toggle_ctr_reg == TOGGLE_DELAY_CYCLES)
+        begin
+          toggle_ctr_new = 32'h0;
+          toggle_we      = 1'b1;
+        end
+      else
+        begin
+          toggle_ctr_new = toggle_ctr_reg + 1'b1;
+          toggle_we      = 1'b0;
+        end
+    end
+
+endmodule // toggle
+
+//======================================================================
+// EOF toggle.v
+//======================================================================
-- 
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