Adding rtl and tb for the csprng part of the trng.

2 files changed, 1047 insertions, 0 deletions

diff --git a/src/rtl/trng_csprng.v b/src/rtl/trng_csprng.v
new file mode 100644
index 0000000..4d472d2
--- /dev/null
+++ b/src/rtl/trng_csprng.v
@@ -0,0 +1,497 @@
+//======================================================================
+//
+// trng_csprng.v
+// -------------
+// CSPRNG for the TRNG.
+//
+//
+// Author: Joachim Strombergson
+// Copyright (c) 2014, 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 trng_csprng(
+                   // Clock and reset.
+                   input wire           clk,
+                   input wire           reset_n,
+
+                   // Control, config and status.
+                   input                debug_mode,
+                   input wire [4 : 0]   num_rounds,
+                   input wire [63 : 0]  num_blocks,
+                   input wire           seed,
+                   input wire           enable,
+                   output wire          more_seed,
+                   output wire          ready,
+                   output wire          error,
+
+                   // Seed input
+                   input wire           seed_syn,
+                   input [511 : 0]      seed_data,
+                   output wire          seed_ack,
+
+                   // Random data output
+                   output wire          rnd_syn,
+                   output wire [31 : 0] rnd_data,
+                   input wire           rnd_ack
+                  );
+
+
+  //----------------------------------------------------------------
+  // Internal constant and parameter definitions.
+  //----------------------------------------------------------------
+  parameter CIPHER_KEYLEN256  = 1'b1; // 256 bit key.
+  parameter CIPHER_MAX_BLOCKS = 64'h1000000000000000;
+
+  parameter CTRL_IDLE      = 4'h0;
+  parameter CTRL_SEED0     = 4'h1;
+  parameter CTRL_SEED1     = 4'h2;
+  parameter CTRL_INIT0     = 4'h3;
+  parameter CTRL_INIT1     = 4'h4;
+  parameter CTRL_NEXT0     = 4'h5;
+  parameter CTRL_NEXT1     = 4'h6;
+  parameter CTRL_MORE      = 4'h7;
+  parameter CTRL_CANCEL    = 4'hf;
+
+
+  //----------------------------------------------------------------
+  // Registers including update variables and write enable.
+  //----------------------------------------------------------------
+  reg [255 : 0] cipher_key_reg;
+  reg [255 : 0] cipher_key_new;
+  reg           cipher_key_we;
+
+  reg [63 : 0]  cipher_iv_reg;
+  reg [63 : 0]  cipher_iv_new;
+  reg           cipher_iv_we;
+
+  reg [63 : 0]  cipher_ctr_reg;
+  reg [63 : 0]  cipher_ctr_new;
+  reg           cipher_ctr_we;
+
+  reg [511 : 0] cipher_block_reg;
+  reg [511 : 0] cipher_block_new;
+  reg           cipher_block_we;
+
+  reg [63 : 0]  block_ctr_reg;
+  reg [63 : 0]  block_ctr_new;
+  reg           block_ctr_inc;
+  reg           block_ctr_rst;
+  reg           block_ctr_we;
+  reg           block_ctr_max;
+
+  reg           error_reg;
+  reg           error_new;
+  reg           error_we;
+
+  reg [3 : 0]   csprng_ctrl_reg;
+  reg [3 : 0]   csprng_ctrl_new;
+  reg           csprng_ctrl_we;
+
+  reg           ready_reg;
+  reg           ready_new;
+  reg           ready_we;
+
+  reg           more_seed_reg;
+  reg           more_seed_new;
+
+  reg           seed_ack_reg;
+  reg           seed_ack_new;
+
+
+  //----------------------------------------------------------------
+  // Wires.
+  //----------------------------------------------------------------
+  reg            cipher_init;
+  reg            cipher_next;
+
+  wire [511 : 0] cipher_data_out;
+  wire           cipher_data_out_valid;
+
+  reg            discard_outputs;
+
+  wire           fifo_more_data;
+  reg            fifo_discard;
+  wire           fifo_rnd_syn;
+  wire [31 : 0]  fifo_rnd_data;
+  reg            fifo_cipher_data_valid;
+
+
+  //----------------------------------------------------------------
+  // Concurrent connectivity for ports etc.
+  //----------------------------------------------------------------
+  assign seed_ack  = seed_ack_reg;
+  assign more_seed = more_seed_reg;
+
+  assign ready     = ready_reg;
+  assign error     = error_reg;
+
+  assign rnd_syn   = fifo_rnd_syn;
+  assign rnd_data  = fifo_rnd_data;
+
+
+  //----------------------------------------------------------------
+  // core instantiation.
+  //----------------------------------------------------------------
+  chacha_core cipher(
+                     .clk(clk),
+                     .reset_n(reset_n),
+
+                     .init(cipher_init),
+                     .next(cipher_next),
+
+                     .key(cipher_key_reg),
+                     .keylen(CIPHER_KEYLEN256),
+                     .iv(cipher_iv_reg),
+                     .ctr(cipher_ctr_reg),
+                     .rounds(num_rounds),
+
+                     .data_in(cipher_block_reg),
+                     .ready(cipher_ready),
+
+                     .data_out(cipher_data_out),
+                     .data_out_valid(cipher_data_out_valid)
+                    );
+
+
+  trng_csprng_fifo fifo(
+                        .clk(clk),
+                        .reset_n(reset_n),
+
+                        .csprng_data(cipher_data_out),
+                        .csprng_data_valid(fifo_cipher_data_valid),
+                        .discard(fifo_discard),
+                        .more_data(fifo_more_data),
+
+                        .rnd_syn(fifo_rnd_syn),
+                        .rnd_data(fifo_rnd_data),
+                        .rnd_ack(rnd_ack)
+                       );
+
+
+  //----------------------------------------------------------------
+  // reg_update
+  //
+  // Update functionality for all registers in the core.
+  // All registers are positive edge triggered with synchronous
+  // active low reset. All registers have write enable.
+  //----------------------------------------------------------------
+  always @ (posedge clk or negedge reset_n)
+    begin
+      if (!reset_n)
+        begin
+          cipher_key_reg   <= {8{32'h00000000}};
+          cipher_iv_reg    <= {2{32'h00000000}};
+          cipher_ctr_reg   <= {2{32'h00000000}};
+          cipher_block_reg <= {16{32'h00000000}};
+          block_ctr_reg    <= {2{32'h00000000}};
+          more_seed_reg    <= 0;
+          seed_ack_reg     <= 0;
+          ready_reg        <= 0;
+          error_reg        <= 0;
+          csprng_ctrl_reg  <= CTRL_IDLE;
+        end
+      else
+        begin
+          more_seed_reg <= more_seed_new;
+          seed_ack_reg  <= seed_ack_new;
+
+          if (cipher_key_we)
+            begin
+              cipher_key_reg <= cipher_key_new;
+            end
+
+          if (cipher_iv_we)
+            begin
+              cipher_iv_reg <= cipher_iv_new;
+            end
+
+          if (cipher_ctr_we)
+            begin
+              cipher_ctr_reg <= cipher_ctr_new;
+            end
+
+          if (cipher_block_we)
+            begin
+              cipher_block_reg <= cipher_block_new;
+            end
+
+          if (block_ctr_we)
+            begin
+              block_ctr_reg <= block_ctr_new;
+            end
+
+          if (ready_we)
+            begin
+              ready_reg <= ready_new;
+            end
+
+          if (error_we)
+            begin
+              error_reg <= error_new;
+            end
+
+          if (csprng_ctrl_we)
+            begin
+              csprng_ctrl_reg <= csprng_ctrl_new;
+            end
+        end
+    end // reg_update
+
+
+  //----------------------------------------------------------------
+  // block_ctr
+  //
+  // Logic to implement the block counter. This includes the
+  // ability to detect that maximum allowed number of blocks
+  // has been reached. Either as defined by the application
+  // or the hard coded CIPHER_MAX_BLOCKS value.
+  //----------------------------------------------------------------
+  always @*
+    begin : block_ctr
+      block_ctr_new = 64'h0000000000000000;
+      block_ctr_we  = 0;
+      block_ctr_max = 0;
+
+      if (block_ctr_rst)
+        begin
+          block_ctr_new = 64'h0000000000000000;
+          block_ctr_we  = 1;
+        end
+
+      if (block_ctr_inc)
+        begin
+          block_ctr_new = block_ctr_reg + 1'b1;
+          block_ctr_we  = 1;
+        end
+
+      if ((block_ctr_reg == num_blocks) || (block_ctr_reg == CIPHER_MAX_BLOCKS))
+        begin
+          block_ctr_max = 1;
+        end
+    end // block_ctr
+
+
+  //----------------------------------------------------------------
+  // csprng_ctrl_fsm
+  //
+  // Control FSM for the CSPRNG.
+  //----------------------------------------------------------------
+  always @*
+    begin : csprng_ctrl_fsm
+      cipher_key_new         = {8{32'h00000000}};
+      cipher_key_we          = 0;
+      cipher_iv_new          = {2{32'h00000000}};
+      cipher_iv_we           = 0;
+      cipher_ctr_new         = {2{32'h00000000}};
+      cipher_ctr_we          = 0;
+      cipher_block_new       = {16{32'h00000000}};
+      cipher_block_we        = 0;
+      cipher_init            = 0;
+      cipher_next            = 0;
+      block_ctr_rst          = 0;
+      block_ctr_inc          = 0;
+      ready_new              = 0;
+      ready_we               = 0;
+      error_new              = 0;
+      error_we               = 0;
+      discard_outputs        = 0;
+      seed_ack_new           = 0;
+      more_seed_new          = 0;
+      fifo_discard           = 0;
+      fifo_cipher_data_valid = 0;
+      csprng_ctrl_new        = CTRL_IDLE;
+      csprng_ctrl_we         = 0;
+
+      case (csprng_ctrl_reg)
+        CTRL_IDLE:
+          begin
+            if (!enable)
+              begin
+                csprng_ctrl_new = CTRL_CANCEL;
+                csprng_ctrl_we  = 1;
+              end
+            else if (fifo_more_data)
+              begin
+                more_seed_new   = 1;
+                csprng_ctrl_new = CTRL_SEED0;
+                csprng_ctrl_we  = 1;
+              end
+          end
+
+        CTRL_SEED0:
+          begin
+            if ((!enable) || (seed))
+              begin
+                csprng_ctrl_new = CTRL_CANCEL;
+                csprng_ctrl_we  = 1;
+              end
+            else if (seed_syn)
+              begin
+                more_seed_new    = 1;
+                seed_ack_new     = 1;
+                cipher_block_new = seed_data;
+                cipher_block_we  = 1;
+                csprng_ctrl_new  = CTRL_SEED1;
+                csprng_ctrl_we   = 1;
+              end
+          end
+
+        CTRL_SEED1:
+          begin
+            if ((!enable) || (seed))
+              begin
+                csprng_ctrl_new = CTRL_CANCEL;
+                csprng_ctrl_we  = 1;
+              end
+            else if (seed_syn)
+              begin
+                seed_ack_new    = 1;
+                cipher_key_new  = seed_data[255 : 0];
+                cipher_key_we   = 1;
+                cipher_iv_new   = seed_data[319 : 256];
+                cipher_iv_we    = 1;
+                cipher_ctr_new  = seed_data[383 : 320];
+                cipher_ctr_we   = 1;
+                csprng_ctrl_new = CTRL_INIT0;
+                csprng_ctrl_we  = 1;
+              end
+            else
+              begin
+                more_seed_new = 1;
+              end
+          end
+
+        CTRL_INIT0:
+          begin
+            if ((!enable) || (seed))
+              begin
+                csprng_ctrl_new = CTRL_CANCEL;
+                csprng_ctrl_we  = 1;
+              end
+            else
+              begin
+                cipher_init     = 1;
+                block_ctr_rst   = 1;
+                csprng_ctrl_new = CTRL_INIT1;
+                csprng_ctrl_we  = 1;
+              end
+          end
+
+        CTRL_INIT1:
+          begin
+            if ((!enable) || (seed))
+              begin
+                csprng_ctrl_new = CTRL_CANCEL;
+                csprng_ctrl_we  = 1;
+              end
+            else if (cipher_ready)
+              begin
+                csprng_ctrl_new = CTRL_NEXT0;
+                csprng_ctrl_we  = 1;
+              end
+          end
+
+        CTRL_NEXT0:
+          begin
+            if ((!enable) || (seed))
+              begin
+                csprng_ctrl_new = CTRL_CANCEL;
+                csprng_ctrl_we  = 1;
+              end
+            else
+              begin
+                cipher_next     = 1;
+                csprng_ctrl_new = CTRL_NEXT1;
+                csprng_ctrl_we  = 1;
+              end
+          end
+
+        CTRL_NEXT1:
+            if ((!enable) || (seed))
+              begin
+                csprng_ctrl_new = CTRL_CANCEL;
+                csprng_ctrl_we  = 1;
+              end
+            else if (cipher_ready)
+              begin
+                block_ctr_inc          = 1;
+                fifo_cipher_data_valid = 1;
+                csprng_ctrl_new        = CTRL_MORE;
+                csprng_ctrl_we         = 1;
+              end
+
+        CTRL_MORE:
+          begin
+            if ((!enable) || (seed))
+              begin
+                csprng_ctrl_new = CTRL_CANCEL;
+                csprng_ctrl_we  = 1;
+              end
+            else if (fifo_more_data)
+              begin
+                if (block_ctr_max)
+                  begin
+                    more_seed_new   = 1;
+                    csprng_ctrl_new = CTRL_SEED0;
+                    csprng_ctrl_we  = 1;
+                  end
+                else
+                  begin
+                    csprng_ctrl_new = CTRL_NEXT0;
+                    csprng_ctrl_we  = 1;
+                  end
+              end
+          end
+
+        CTRL_CANCEL:
+          begin
+            fifo_discard     = 1;
+            cipher_key_new   = {8{32'h00000000}};
+            cipher_key_we    = 1;
+            cipher_iv_new    = {2{32'h00000000}};
+            cipher_iv_we     = 1;
+            cipher_ctr_new   = {2{32'h00000000}};
+            cipher_ctr_we    = 1;
+            cipher_block_new = {16{32'h00000000}};
+            cipher_block_we  = 1;
+            block_ctr_rst    = 1;
+            discard_outputs  = 1;
+            csprng_ctrl_new  = CTRL_IDLE;
+            csprng_ctrl_we   = 1;
+          end
+
+      endcase // case (cspng_ctrl_reg)
+    end // csprng_ctrl_fsm
+
+endmodule // trng_csprng
+
+//======================================================================
+// EOF trng_csprng.v
+//======================================================================
diff --git a/src/rtl/trng_csprng_fifo.v b/src/rtl/trng_csprng_fifo.v
new file mode 100644
index 0000000..4d908f9
--- /dev/null
+++ b/src/rtl/trng_csprng_fifo.v
@@ -0,0 +1,550 @@
+//======================================================================
+//
+// trng_csprng_fifo.v
+// ------------------
+// Output FIFO for the CSPRNG in the TRNG.
+//
+//
+// Author: Joachim Strombergson
+// Copyright (c) 2014, 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 trng_csprng_fifo(
+                        // Clock and reset.
+                        input wire           clk,
+                        input wire           reset_n,
+
+                        input wire [511 : 0] csprng_data,
+                        input wire           csprng_data_valid,
+                        input wire           discard,
+                        output wire          more_data,
+
+                        output wire          rnd_syn,
+                        output wire [31 : 0] rnd_data,
+                        input wire           rnd_ack
+                       );
+
+
+  //----------------------------------------------------------------
+  // Internal constant and parameter definitions.
+  //----------------------------------------------------------------
+  parameter FIFO_DEPTH = 32;
+  parameter FIFO_MAX = FIFO_DEPTH - 1;
+
+  parameter WR_IDLE    = 0;
+  parameter WR_WAIT    = 1;
+  parameter WR_WRITE   = 2;
+  parameter WR_DISCARD = 7;
+
+  parameter RD_IDLE    = 0;
+  parameter RD_ACK     = 1;
+  parameter RD_DISCARD = 7;
+
+
+  //----------------------------------------------------------------
+  // Registers including update variables and write enable.
+  //----------------------------------------------------------------
+  reg [31 : 0] fifo_mem [0 : FIFO_MAX];
+  reg          fifo_mem_we;
+
+  reg [3 : 0] mux_data_ptr_reg;
+  reg [3 : 0] mux_data_ptr_new;
+  reg         mux_data_ptr_inc;
+  reg         mux_data_ptr_rst;
+  reg         mux_data_ptr_we;
+
+  reg [7 : 0] wr_ptr_reg;
+  reg [7 : 0] wr_ptr_new;
+  reg         wr_ptr_inc;
+  reg         wr_ptr_rst;
+  reg         wr_ptr_we;
+
+  reg [7 : 0] rd_ptr_reg;
+  reg [7 : 0] rd_ptr_new;
+  reg         rd_ptr_inc;
+  reg         rd_ptr_rst;
+  reg         rd_ptr_we;
+
+  reg [31 : 0] rnd_data_reg;
+
+  reg          rnd_syn_reg;
+  reg          rnd_syn_new;
+  reg          rnd_syn_we;
+
+  reg [2 : 0]  wr_ctrl_reg;
+  reg [2 : 0]  wr_ctrl_new;
+  reg          wr_ctrl_we;
+
+  reg [2 : 0]  rd_ctrl_reg;
+  reg [2 : 0]  rd_ctrl_new;
+  reg          rd_ctrl_we;
+
+  reg [5 : 0]  fifo_ctr_reg;
+  reg [5 : 0]  fifo_ctr_new;
+  reg          fifo_ctr_inc;
+  reg          fifo_ctr_dec;
+  reg          fifo_ctr_rst;
+  reg          fifo_ctr_we;
+  reg          fifo_empty;
+  reg          fifo_full;
+
+  reg          more_data_reg;
+  reg          more_data_new;
+  reg          more_data_we;
+
+
+  //----------------------------------------------------------------
+  // Wires.
+  //----------------------------------------------------------------
+  reg [31 : 0] muxed_data;
+
+
+  //----------------------------------------------------------------
+  // Concurrent connectivity for ports etc.
+  //----------------------------------------------------------------
+  assign rnd_data = rnd_data_reg;
+  assign rnd_syn  = rnd_syn_reg;
+  assign more_data = more_data_reg;
+
+
+  //----------------------------------------------------------------
+  // reg_update
+  //----------------------------------------------------------------
+  always @ (posedge clk or negedge reset_n)
+    begin
+      if (!reset_n)
+        begin
+          fifo_mem[00]     <= 32'h00000000;
+          fifo_mem[01]     <= 32'h00000000;
+          fifo_mem[02]     <= 32'h00000000;
+          fifo_mem[03]     <= 32'h00000000;
+          fifo_mem[04]     <= 32'h00000000;
+          fifo_mem[05]     <= 32'h00000000;
+          fifo_mem[06]     <= 32'h00000000;
+          fifo_mem[07]     <= 32'h00000000;
+          fifo_mem[08]     <= 32'h00000000;
+          fifo_mem[09]     <= 32'h00000000;
+          fifo_mem[10]     <= 32'h00000000;
+          fifo_mem[11]     <= 32'h00000000;
+          fifo_mem[12]     <= 32'h00000000;
+          fifo_mem[13]     <= 32'h00000000;
+          fifo_mem[14]     <= 32'h00000000;
+          fifo_mem[15]     <= 32'h00000000;
+          fifo_mem[16]     <= 32'h00000000;
+          fifo_mem[17]     <= 32'h00000000;
+          fifo_mem[18]     <= 32'h00000000;
+          fifo_mem[19]     <= 32'h00000000;
+          fifo_mem[20]     <= 32'h00000000;
+          fifo_mem[21]     <= 32'h00000000;
+          fifo_mem[22]     <= 32'h00000000;
+          fifo_mem[23]     <= 32'h00000000;
+          fifo_mem[24]     <= 32'h00000000;
+          fifo_mem[25]     <= 32'h00000000;
+          fifo_mem[26]     <= 32'h00000000;
+          fifo_mem[27]     <= 32'h00000000;
+          fifo_mem[28]     <= 32'h00000000;
+          fifo_mem[29]     <= 32'h00000000;
+          fifo_mem[30]     <= 32'h00000000;
+          fifo_mem[31]     <= 32'h00000000;
+
+          mux_data_ptr_reg <= 4'h0;
+          wr_ptr_reg       <= 8'h00;
+          rd_ptr_reg       <= 8'h00;
+          fifo_ctr_reg     <= 6'h00;
+          rnd_data_reg     <= 32'h00000000;
+          rnd_syn_reg      <= 0;
+          more_data_reg    <= 0;
+          wr_ctrl_reg      <= 3'h0;
+          rd_ctrl_reg      <= 3'h0;
+        end
+      else
+        begin
+          rnd_data_reg <= fifo_mem[rd_ptr_reg];
+
+          if (rnd_syn_we)
+            begin
+              rnd_syn_reg  <= rnd_syn_new;
+            end
+
+          if (fifo_mem_we)
+            begin
+              fifo_mem[wr_ptr_reg] <= muxed_data;
+            end
+
+          if (mux_data_ptr_we)
+            begin
+              mux_data_ptr_reg <= mux_data_ptr_new;
+            end
+
+          if (wr_ptr_we)
+            begin
+              wr_ptr_reg <= wr_ptr_new;
+            end
+
+          if (rd_ptr_we)
+            begin
+              rd_ptr_reg <= rd_ptr_new;
+            end
+
+          if (fifo_ctr_we)
+            begin
+              fifo_ctr_reg <= fifo_ctr_new;
+            end
+
+          if (more_data_we)
+            begin
+              more_data_reg <= more_data_new;
+            end
+
+          if (wr_ctrl_we)
+            begin
+              wr_ctrl_reg <= wr_ctrl_new;
+            end
+
+          if (rd_ctrl_we)
+            begin
+              rd_ctrl_reg <= rd_ctrl_new;
+            end
+        end
+    end // reg_update
+
+
+  //----------------------------------------------------------------
+  // data_mux
+  //----------------------------------------------------------------
+  always @*
+    begin : data_mux
+      case(mux_data_ptr_reg)
+        00: muxed_data = csprng_data[031 : 000];
+        01: muxed_data = csprng_data[063 : 032];
+        02: muxed_data = csprng_data[095 : 064];
+        03: muxed_data = csprng_data[127 : 096];
+        04: muxed_data = csprng_data[159 : 128];
+        05: muxed_data = csprng_data[191 : 160];
+        06: muxed_data = csprng_data[223 : 192];
+        07: muxed_data = csprng_data[255 : 224];
+        08: muxed_data = csprng_data[287 : 256];
+        09: muxed_data = csprng_data[313 : 282];
+        10: muxed_data = csprng_data[351 : 320];
+        11: muxed_data = csprng_data[383 : 351];
+        12: muxed_data = csprng_data[415 : 384];
+        13: muxed_data = csprng_data[447 : 416];
+        14: muxed_data = csprng_data[479 : 448];
+        15: muxed_data = csprng_data[511 : 480];
+      endcase // case (mux_data_ptr_reg)
+    end // data_mux
+
+
+  //----------------------------------------------------------------
+  // mux_data_ptr
+  //----------------------------------------------------------------
+  always @*
+    begin : mux_data_ptr
+      mux_data_ptr_new = 4'h0;
+      mux_data_ptr_we  = 0;
+
+      if (mux_data_ptr_rst)
+        begin
+          mux_data_ptr_new = 4'h0;
+          mux_data_ptr_we  = 1;
+        end
+
+      if (mux_data_ptr_inc)
+        begin
+          mux_data_ptr_new = mux_data_ptr_reg + 1'b1;
+          mux_data_ptr_we  = 1;
+        end
+    end // mux_data_ptr
+
+
+  //----------------------------------------------------------------
+  // fifo_rd_ptr
+  //----------------------------------------------------------------
+  always @*
+    begin : fifo_rd_ptr
+      rd_ptr_new = 8'h00;
+      rd_ptr_we  = 0;
+
+      if (rd_ptr_rst)
+        begin
+          rd_ptr_new = 8'h00;
+          rd_ptr_we  = 1;
+        end
+
+      if (rd_ptr_inc)
+        begin
+          if (rd_ptr_reg == FIFO_MAX)
+            begin
+              rd_ptr_new = 8'h00;
+              rd_ptr_we  = 1;
+            end
+          else
+            begin
+              rd_ptr_new = rd_ptr_reg + 1'b1;
+              rd_ptr_we  = 1;
+            end
+        end
+    end // fifo_rd_ptr
+
+
+  //----------------------------------------------------------------
+  // fifo_wr_ptr
+  //----------------------------------------------------------------
+  always @*
+    begin : fifo_wr_ptr
+      wr_ptr_new = 8'h00;
+      wr_ptr_we  = 0;
+
+      if (wr_ptr_rst)
+        begin
+          wr_ptr_new = 8'h00;
+          wr_ptr_we  = 1;
+        end
+
+      if (wr_ptr_inc)
+        begin
+          if (wr_ptr_reg == FIFO_MAX)
+            begin
+              wr_ptr_new = 8'h00;
+              wr_ptr_we  = 1;
+            end
+          else
+            begin
+              wr_ptr_new = wr_ptr_reg + 1'b1;
+              wr_ptr_we  = 1;
+            end
+        end
+    end // fifo_wr_ptr
+
+
+  //----------------------------------------------------------------
+  // fifo_ctr
+  //
+  // fifo counter tracks the number of elements and provides
+  // signals for full and empty fifo.
+  //----------------------------------------------------------------
+  always @*
+    begin : fifo_ctr
+      fifo_empty = 0;
+      fifo_full = 0;
+      fifo_ctr_new = 6'h00;
+      fifo_ctr_we  = 0;
+
+      if (fifo_ctr_reg == FIFO_DEPTH)
+        begin
+          fifo_full = 1;
+        end
+
+      if (fifo_ctr_reg < 6'h0f)
+        begin
+          fifo_empty = 1;
+        end
+
+      if (fifo_ctr_inc)
+        begin
+          fifo_ctr_new = fifo_ctr_reg + 1'b1;
+          fifo_ctr_we  = 1;
+        end
+
+      if (fifo_ctr_dec)
+        begin
+          fifo_ctr_new = fifo_ctr_reg - 1'b1;
+          fifo_ctr_we  = 1;
+        end
+
+      if (fifo_ctr_rst)
+        begin
+          fifo_ctr_new = 6'h00;
+          fifo_ctr_we  = 1;
+        end
+    end // fifo_ctr
+
+
+  //----------------------------------------------------------------
+  // rd_ctrl
+  //----------------------------------------------------------------
+  always @*
+    begin : rd_ctrl
+      fifo_ctr_dec = 0;
+      rnd_syn_new  = 0;
+      rnd_syn_we   = 0;
+      rd_ptr_inc   = 0;
+      rd_ptr_rst   = 0;
+      rd_ctrl_new  = RD_IDLE;
+      rd_ctrl_we   = 0;
+
+      case (rd_ctrl_reg)
+        RD_IDLE:
+          begin
+            if (discard)
+              begin
+                rd_ctrl_new = RD_DISCARD;
+                rd_ctrl_we  = 1;
+              end
+            else
+              begin
+                if (!fifo_empty)
+                  begin
+                    rnd_syn_new = 1;
+                    rnd_syn_we  = 1;
+                    rd_ctrl_new = RD_ACK;
+                    rd_ctrl_we  = 1;
+                  end
+              end
+          end
+
+        RD_ACK:
+          begin
+            if (discard)
+              begin
+                rd_ctrl_new = RD_DISCARD;
+                rd_ctrl_we  = 1;
+              end
+            else
+              begin
+                if (rnd_ack)
+                  begin
+                    fifo_ctr_dec = 1;
+                    rd_ptr_inc   = 1;
+                    rnd_syn_new  = 0;
+                    rnd_syn_we   = 1;
+                    rd_ctrl_new  = RD_IDLE;
+                    rd_ctrl_we   = 1;
+                  end
+              end
+          end
+
+        RD_DISCARD:
+          begin
+            rnd_syn_new = 0;
+            rnd_syn_we  = 1;
+            rd_ptr_rst  = 1;
+            rd_ctrl_new = RD_IDLE;
+            rd_ctrl_we  = 1;
+
+          end
+
+      endcase // case (rd_ctrl_reg)
+
+    end // rd_ctrl
+
+
+  //----------------------------------------------------------------
+  // wr_ctrl
+  //----------------------------------------------------------------
+  always @*
+    begin : wr_ctrl
+      more_data_new    = 0;
+      more_data_we     = 0;
+      mux_data_ptr_rst = 0;
+      mux_data_ptr_inc = 0;
+      wr_ptr_inc       = 0;
+      wr_ptr_rst       = 0;
+      fifo_mem_we      = 0;
+      fifo_ctr_inc     = 0;
+      fifo_ctr_rst     = 0;
+      wr_ctrl_new      = WR_IDLE;
+      wr_ctrl_we       = 0;
+
+      case (wr_ctrl_reg)
+        WR_IDLE:
+          begin
+            if (discard)
+              begin
+                wr_ctrl_new = WR_DISCARD;
+                wr_ctrl_we  = 1;
+              end
+            else if (!fifo_full)
+              begin
+                more_data_new = 1;
+                more_data_we  = 1;
+                wr_ctrl_new   = WR_WAIT;
+                wr_ctrl_we    = 1;
+              end
+          end
+
+        WR_WAIT:
+          begin
+            if (discard)
+              begin
+                wr_ctrl_new      = WR_DISCARD;
+                wr_ctrl_we       = 1;
+              end
+            else if (csprng_data_valid)
+              begin
+                more_data_new    = 0;
+                more_data_we     = 1;
+                mux_data_ptr_rst = 1;
+                wr_ctrl_new      = WR_WRITE;
+                wr_ctrl_we       = 1;
+              end
+          end
+
+        WR_WRITE:
+          begin
+            if (discard)
+              begin
+                wr_ctrl_new      = WR_DISCARD;
+                wr_ctrl_we       = 1;
+              end
+            else if (!fifo_full)
+              begin
+                fifo_mem_we      = 1;
+                wr_ptr_inc       = 1;
+                mux_data_ptr_inc = 1;
+                fifo_ctr_inc     = 1;
+
+                if (mux_data_ptr_new == 4'h0)
+                  begin
+                    wr_ctrl_new = WR_IDLE;
+                    wr_ctrl_we  = 1;
+                  end
+              end
+          end
+
+        WR_DISCARD:
+          begin
+            fifo_ctr_rst     = 1;
+            more_data_new    = 0;
+            more_data_we     = 1;
+            mux_data_ptr_rst = 1;
+            wr_ptr_rst       = 1;
+            wr_ctrl_new      = WR_IDLE;
+            wr_ctrl_we       = 1;
+          end
+      endcase // case (wr_ctrl_reg)
+
+    end // wr_ctrl
+
+endmodule // trng_csprng_fifo
+
+//======================================================================
+// EOF trng_csprng_fifo.v
+//======================================================================