Adding first iteration of FPGA test design.

1 files changed, 174 insertions, 0 deletions

diff --git a/src/rtl/external_avalanche_entropy.v b/src/rtl/external_avalanche_entropy.v
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+++ b/src/rtl/external_avalanche_entropy.v
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+//======================================================================
+//
+// external_avalanche_entropy.v
+// ----------------------------
+// Entropy provider for an external entropy source based on
+// avalanche noise. (or any other source that ca toggle a single
+// bit input).
+//
+// Currently the design consists of a free running counter. At every
+// positive flank detected the LSB of the counter is pushed into
+// a 32bit shift register.
+//
+//
+// Author: Joachim Strombergson
+// Copyright (c) 2011, 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 external_avalanche_entropy(
+                                  input wire          clk,
+                                  input wire          reset_n,
+
+                                  input wire          noise,
+  
+                                  output wire [7 : 0] debug
+                                  );
+
+  //----------------------------------------------------------------
+  // Internal constant and parameter definitions.
+  //----------------------------------------------------------------
+  parameter DEBUG_RATE = 32'h00300000;
+  
+  
+  //----------------------------------------------------------------
+  // Registers including update variables and write enable.
+  //----------------------------------------------------------------
+  reg noise_sample_reg;
+
+  reg flank0_reg;
+  reg flank1_reg;
+
+  reg [31 : 0] cycle_ctr_reg;
+
+  reg [31 : 0] entropy_reg;
+  reg [31 : 0] entropy_new;
+  reg          entropy_we;
+  
+  reg [31 : 0] debug_ctr_reg;
+  reg [31 : 0] debug_ctr_new;
+  reg          debug_ctr_we;
+  
+  reg [7 : 0] debug_reg;
+  reg [7 : 0] debug_new;
+  reg         debug_we;
+
+  
+  //----------------------------------------------------------------
+  // Concurrent connectivity for ports etc.
+  //----------------------------------------------------------------
+  assign debug = debug_reg;
+  
+  
+  //----------------------------------------------------------------
+  // reg_update
+  //----------------------------------------------------------------
+  always @ (posedge clk or negedge reset_n)
+    begin
+      if (!reset_n)
+        begin
+          noise_sample_reg <= 1'b0;
+          flank0_reg       <= 1'b0;
+          flank1_reg       <= 1'b0;
+          cycle_ctr_reg    <= 32'h00000000;
+          debug_ctr_reg    <= 32'h00000000;
+          entropy_reg      <= 32'h00000000;
+          debug_reg        <= 8'h00;
+        end
+      else
+        begin
+          noise_sample_reg <= noise;
+
+          flank0_reg <= noise_sample_reg;
+          flank1_reg <= flank0_reg;
+
+          cycle_ctr_reg <= cycle_ctr_reg + 1'b1;
+          debug_ctr_reg <= debug_ctr_new;
+          
+          if (entropy_we)
+            begin
+              entropy_reg <= entropy_new;
+            end
+
+          if (debug_we)
+            begin
+              debug_reg <= debug_new;
+            end
+        end
+    end // reg_update
+
+
+  //----------------------------------------------------------------
+  // entropy_collect
+  //
+  // This is where we collect entropy by adding the LSB of the
+  // cycle counter to the entropy shift register every time
+  // we detect a positive flank at the noise source.
+  //----------------------------------------------------------------
+  always @*
+    begin : entropy_collect
+      entropy_new = 32'h00000000;
+      entropy_we  = 1'b0;
+
+      // Update the entropy shift register every positive flank.
+      if ((flank0_reg) && (flank1_reg))
+        begin
+          entropy_new = {entropy_reg[30 : 0], cycle_ctr_reg[0]};
+          entropy_we  = 1'b1;
+        end
+    end // entropy_collect
+  
+
+  //----------------------------------------------------------------
+  // debug_update
+  //
+  // Sample the entropy register as debug value at the given
+  // DEBUG_RATE.
+  //----------------------------------------------------------------
+  always @*
+    begin : debug_update
+      debug_ctr_new = debug_ctr_reg + 1'b1;
+      debug_new     = entropy_reg[7 : 0];
+      debug_we      = 1'b0;
+
+      if (debug_ctr_reg == DEBUG_RATE)
+        begin
+          debug_ctr_new = 32'h00000000;
+          debug_we = 1'b1;
+        end
+    end // debug_update
+  
+endmodule // external_avalanche_entropy
+
+//======================================================================
+// EOF external_avalanche_entropy.v
+//======================================================================