[Cryptech-Commits] [core/trng] 02/02: Reworked the csprng output fifo to really take advantage of the fact that the csprng delivers blocks of 512 bits. Removed trailing whitespaces and linted code.

git at cryptech.is git at cryptech.is
Thu Nov 20 11:04:38 UTC 2014


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joachim at secworks.se pushed a commit to branch master
in repository core/trng.

commit 376be260fba6b04a1552d9be4b53bfa4274a6911
Author: Joachim Strömbergson <joachim at secworks.se>
Date:   Thu Nov 20 12:04:29 2014 +0100

    Reworked the csprng output fifo to really take advantage of the fact that the csprng delivers blocks of 512 bits. Removed trailing whitespaces and linted code.
---
 src/rtl/trng_csprng_fifo.v | 417 ++++++++++++++++++++-------------------------
 1 file changed, 187 insertions(+), 230 deletions(-)

diff --git a/src/rtl/trng_csprng_fifo.v b/src/rtl/trng_csprng_fifo.v
index f71a152..b6ff2c1 100644
--- a/src/rtl/trng_csprng_fifo.v
+++ b/src/rtl/trng_csprng_fifo.v
@@ -6,33 +6,33 @@
 //
 //
 // Author: Joachim Strombergson
-// Copyright (c) 2014, NORDUnet A/S All rights reserved.
+// Copyright (c) 2014, SUNET
+// 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.
+// Redistribution and use in source and binary forms, with or
+// without modification, are permitted provided that the following
+// conditions are met:
 //
-// - 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.
+// 1. Redistributions of source code must retain the above copyright
+//    notice, this list of conditions and the following disclaimer.
 //
-// - 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.
+// 2. 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.
 //
-// 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.
+// 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 OWNER 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.
 //
 //======================================================================
 
@@ -55,8 +55,8 @@ module trng_csprng_fifo(
   //----------------------------------------------------------------
   // Internal constant and parameter definitions.
   //----------------------------------------------------------------
-  parameter FIFO_DEPTH = 32;
-  parameter FIFO_MAX = FIFO_DEPTH - 1;
+  parameter FIFO_DEPTH = 4;
+  parameter FIFO_MAX   = FIFO_DEPTH - 1;
 
   parameter WR_IDLE    = 0;
   parameter WR_WAIT    = 1;
@@ -71,53 +71,52 @@ module trng_csprng_fifo(
   //----------------------------------------------------------------
   // 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;
+  reg [511 : 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 [2 : 0]   wr_ptr_reg;
+  reg [2 : 0]   wr_ptr_new;
+  reg           wr_ptr_inc;
+  reg           wr_ptr_rst;
+  reg           wr_ptr_we;
+
+  reg [2 : 0]   rd_ptr_reg;
+  reg [2 : 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 [2 : 0]   fifo_ctr_reg;
+  reg [2 : 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;
 
 
   //----------------------------------------------------------------
@@ -129,73 +128,47 @@ module trng_csprng_fifo(
   //----------------------------------------------------------------
   // Concurrent connectivity for ports etc.
   //----------------------------------------------------------------
-  assign rnd_data = rnd_data_reg;
-  assign rnd_syn  = rnd_syn_reg;
+  assign rnd_data  = rnd_data_reg;
+  assign rnd_syn   = rnd_syn_reg;
   assign more_data = more_data_reg;
 
 
   //----------------------------------------------------------------
   // reg_update
+  //
+  // Register update. All registers have asynchronous reset.
   //----------------------------------------------------------------
   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;
-
+          fifo_mem[00]     <= {16{32'h00000000}};
+          fifo_mem[01]     <= {16{32'h00000000}};
+          fifo_mem[02]     <= {16{32'h00000000}};
+          fifo_mem[03]     <= {16{32'h00000000}};
           mux_data_ptr_reg <= 4'h0;
-          wr_ptr_reg       <= 8'h00;
-          rd_ptr_reg       <= 8'h00;
-          fifo_ctr_reg     <= 6'h00;
+          wr_ptr_reg       <= 3'h0;
+          rd_ptr_reg       <= 3'h0;
+          fifo_ctr_reg     <= 3'h0;
           rnd_data_reg     <= 32'h00000000;
           rnd_syn_reg      <= 0;
           more_data_reg    <= 0;
-          wr_ctrl_reg      <= 3'h0;
-          rd_ctrl_reg      <= 3'h0;
+          wr_ctrl_reg      <= WR_IDLE;
+          rd_ctrl_reg      <= RD_IDLE;
         end
       else
         begin
-          rnd_data_reg <= fifo_mem[rd_ptr_reg];
+          rnd_data_reg  <= muxed_data;
+          more_data_reg <= more_data_new;
 
           if (rnd_syn_we)
             begin
-              rnd_syn_reg  <= rnd_syn_new;
+              rnd_syn_reg <= rnd_syn_new;
             end
 
           if (fifo_mem_we)
             begin
-              fifo_mem[wr_ptr_reg] <= muxed_data;
+              fifo_mem[wr_ptr_reg] <= csprng_data;
             end
 
           if (mux_data_ptr_we)
@@ -218,52 +191,57 @@ module trng_csprng_fifo(
               fifo_ctr_reg <= fifo_ctr_new;
             end
 
-          if (more_data_we)
+          if (rd_ctrl_we)
             begin
-              more_data_reg <= more_data_new;
+              rd_ctrl_reg <= rd_ctrl_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
+  // output_data_mux
+  //
+  // Logic that reads out a 512 bit word from the fifo memory
+  // and then selects a 32-bit word as output data.
   //----------------------------------------------------------------
   always @*
-    begin : data_mux
+    begin : output_data_mux
+      reg [511 : 0] fifo_rd_data;
+
+      fifo_rd_data = fifo_mem[rd_ptr_reg];
+
       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 : 352];
-        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];
+        00: muxed_data = fifo_rd_data[031 : 000];
+        01: muxed_data = fifo_rd_data[063 : 032];
+        02: muxed_data = fifo_rd_data[095 : 064];
+        03: muxed_data = fifo_rd_data[127 : 096];
+        04: muxed_data = fifo_rd_data[159 : 128];
+        05: muxed_data = fifo_rd_data[191 : 160];
+        06: muxed_data = fifo_rd_data[223 : 192];
+        07: muxed_data = fifo_rd_data[255 : 224];
+        08: muxed_data = fifo_rd_data[287 : 256];
+        09: muxed_data = fifo_rd_data[313 : 282];
+        10: muxed_data = fifo_rd_data[351 : 320];
+        11: muxed_data = fifo_rd_data[383 : 352];
+        12: muxed_data = fifo_rd_data[415 : 384];
+        13: muxed_data = fifo_rd_data[447 : 416];
+        14: muxed_data = fifo_rd_data[479 : 448];
+        15: muxed_data = fifo_rd_data[511 : 480];
       endcase // case (mux_data_ptr_reg)
-    end // data_mux
+    end // output_data_mux
 
 
   //----------------------------------------------------------------
   // mux_data_ptr
+  //
+  // Pointer for selecting output data word from the 512 bit
+  // word currently being read in the FIFO.
   //----------------------------------------------------------------
   always @*
     begin : mux_data_ptr
@@ -286,23 +264,28 @@ module trng_csprng_fifo(
 
   //----------------------------------------------------------------
   // fifo_rd_ptr
+  //
+  // Pointer that selects the current 512 bit word in the FIFO
+  // to extract data from.
   //----------------------------------------------------------------
   always @*
     begin : fifo_rd_ptr
-      rd_ptr_new = 8'h00;
-      rd_ptr_we  = 0;
+      rd_ptr_new   = 3'h0;
+      rd_ptr_we    = 0;
+      fifo_ctr_dec = 0;
 
       if (rd_ptr_rst)
         begin
-          rd_ptr_new = 8'h00;
+          rd_ptr_new = 3'h0;
           rd_ptr_we  = 1;
         end
 
       if (rd_ptr_inc)
         begin
+          fifo_ctr_dec  = 1;
           if (rd_ptr_reg == FIFO_MAX)
             begin
-              rd_ptr_new = 8'h00;
+              rd_ptr_new = 3'h0;
               rd_ptr_we  = 1;
             end
           else
@@ -316,23 +299,25 @@ module trng_csprng_fifo(
 
   //----------------------------------------------------------------
   // fifo_wr_ptr
+  //
+  // Pointer to where to store a new 512 bit word in the FIFO.
   //----------------------------------------------------------------
   always @*
     begin : fifo_wr_ptr
-      wr_ptr_new = 8'h00;
-      wr_ptr_we  = 0;
+      wr_ptr_new   = 3'h0;
+      wr_ptr_we    = 0;
 
       if (wr_ptr_rst)
         begin
-          wr_ptr_new = 8'h00;
-          wr_ptr_we  = 1;
+          wr_ptr_new   = 3'h0;
+          wr_ptr_we    = 1;
         end
 
       if (wr_ptr_inc)
         begin
           if (wr_ptr_reg == FIFO_MAX)
             begin
-              wr_ptr_new = 8'h00;
+              wr_ptr_new = 3'h0;
               wr_ptr_we  = 1;
             end
           else
@@ -347,33 +332,34 @@ module trng_csprng_fifo(
   //----------------------------------------------------------------
   // fifo_ctr
   //
-  // fifo counter tracks the number of elements and provides
-  // signals for full and empty fifo.
+  // fifo counter tracks the number of elements and also signals
+  // the csprng when more data is needed as well as applications
+  // that random numbers are available.
   //----------------------------------------------------------------
   always @*
     begin : fifo_ctr
-      fifo_empty = 0;
-      fifo_full = 0;
-      fifo_ctr_new = 6'h00;
-      fifo_ctr_we  = 0;
+      fifo_ctr_new  = 3'h0;
+      fifo_ctr_we   = 0;
+      fifo_empty    = 0;
+      fifo_full     = 0;
 
-      if (fifo_ctr_reg == FIFO_DEPTH)
+      if (fifo_ctr_reg == 3'h0)
         begin
-          fifo_full = 1;
+          fifo_empty = 1;
         end
 
-      if (fifo_ctr_reg < 6'h0f)
+      if (fifo_ctr_reg == FIFO_MAX)
         begin
-          fifo_empty = 1;
+          fifo_full = 1;
         end
 
-      if (fifo_ctr_inc)
+      if ((fifo_ctr_inc) && (fifo_ctr_reg < FIFO_MAX))
         begin
           fifo_ctr_new = fifo_ctr_reg + 1'b1;
           fifo_ctr_we  = 1;
         end
 
-      if (fifo_ctr_dec)
+      if ((fifo_ctr_dec)  && (fifo_ctr_reg > 3'h0))
         begin
           fifo_ctr_new = fifo_ctr_reg - 1'b1;
           fifo_ctr_we  = 1;
@@ -381,7 +367,7 @@ module trng_csprng_fifo(
 
       if (fifo_ctr_rst)
         begin
-          fifo_ctr_new = 6'h00;
+          fifo_ctr_new = 3'h0;
           fifo_ctr_we  = 1;
         end
     end // fifo_ctr
@@ -389,16 +375,19 @@ module trng_csprng_fifo(
 
   //----------------------------------------------------------------
   // rd_ctrl
+  //
+  // Control FSM for reading data as requested by the consumers.
   //----------------------------------------------------------------
   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;
+      mux_data_ptr_rst = 0;
+      mux_data_ptr_inc = 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:
@@ -431,8 +420,15 @@ module trng_csprng_fifo(
               begin
                 if (rnd_ack)
                   begin
-                    fifo_ctr_dec = 1;
-                    rd_ptr_inc   = 1;
+                    if (mux_data_ptr_reg == 4'hf)
+                      begin
+                        rd_ptr_inc       = 1;
+                        mux_data_ptr_rst = 1;
+                      end
+                    else
+                      begin
+                        mux_data_ptr_inc = 1;
+                      end
                     rnd_syn_new  = 0;
                     rnd_syn_we   = 1;
                     rd_ctrl_new  = RD_IDLE;
@@ -448,30 +444,27 @@ module trng_csprng_fifo(
             rd_ptr_rst  = 1;
             rd_ctrl_new = RD_IDLE;
             rd_ctrl_we  = 1;
-
           end
 
       endcase // case (rd_ctrl_reg)
-
     end // rd_ctrl
 
 
   //----------------------------------------------------------------
   // wr_ctrl
+  //
+  // FSM for requesting data and writing new data to the fifo.
   //----------------------------------------------------------------
   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;
+      wr_ptr_inc    = 0;
+      wr_ptr_rst    = 0;
+      fifo_mem_we   = 0;
+      fifo_ctr_inc  = 0;
+      fifo_ctr_rst  = 0;
+      more_data_new = 0;
+      wr_ctrl_new   = WR_IDLE;
+      wr_ctrl_we    = 0;
 
       case (wr_ctrl_reg)
         WR_IDLE:
@@ -481,50 +474,18 @@ module trng_csprng_fifo(
                 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)
+            else
               begin
-                fifo_mem_we      = 1;
-                wr_ptr_inc       = 1;
-                mux_data_ptr_inc = 1;
-                fifo_ctr_inc     = 1;
+                if (!fifo_full)
+                  begin
+                    more_data_new = 1;
+                  end
 
-                if (mux_data_ptr_new == 4'h0)
+                if (csprng_data_valid)
                   begin
-                    wr_ctrl_new = WR_IDLE;
-                    wr_ctrl_we  = 1;
+                    fifo_mem_we      = 1;
+                    wr_ptr_inc       = 1;
+                    fifo_ctr_inc     = 1;
                   end
               end
           end
@@ -532,15 +493,11 @@ module trng_csprng_fifo(
         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



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