Restructured Verilator libraries

1 files changed, 69 insertions, 0 deletions

diff --git a/library/tlv/pseudo_rand.m4out.tlv b/library/tlv/pseudo_rand.m4out.tlv
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+\m4_TLV_version 1b: tl-x.org
+\SV
+/*
+Copyright (c) 2014, Steven F. Hoover
+
+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.
+    * The name of Steven F. Hoover
+      may not 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 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.
+*/
+
+module pseudo_rand
+  #(parameter WIDTH=257)  // Random vector width, to a max of 257.
+  (input  logic clk,
+   input  logic reset,
+   output logic [WIDTH-1:0] rand_vect
+  );
+
+// Currently, this implements a Galois LFSR.
+// TODO: It should be XORed with something else so it doesn't just shift.
+//       Using polynomials with maximal number of taps would have less regular shifting behavior.
+
+// Bits are numbered in the reverse of the traditional order.  This puts the taps in the lower bit positions.
+
+// Choose optimal parameters for given WIDTH.
+localparam LFSR_WIDTH =
+  (WIDTH <= 64)   ? 64   :
+  (WIDTH <= 128)  ? 128  :
+  (WIDTH <= 257)  ? 257  : 0;   // 257 enables a large non-power of two for replication on an irregular boundary.
+// Polynomial source: http://www.eej.ulst.ac.uk/~ian/modules/EEE515/files/old_files/lfsr/lfsr_table.pdf
+localparam [LFSR_WIDTH-1:0] LFSR_POLY = {{(LFSR_WIDTH-8){1'b0}},
+  (LFSR_WIDTH == 64)   ? 8'b00011011 :
+  (LFSR_WIDTH == 128)  ? 8'b10000111 :
+  (LFSR_WIDTH == 257)  ? 8'b11000101 : 8'b0};
+
+bit [256:0] SEED = 257'h0_7163e168_713d5431_6684e132_5cd84848_f3048b46_76874654_0c45f864_04e4684a;
+
+
+
+\TLV
+   |default
+      @0
+         $reset = reset;
+      @1
+         $lfsr[LFSR_WIDTH-1:0] = $reset ? *SEED : {$lfsr#+1[LFSR_WIDTH-2:0], 1'b0} ^ ({LFSR_WIDTH{$lfsr#+1[LFSR_WIDTH-1]}} & *LFSR_POLY);
+      @2
+         *rand_vect = $lfsr[WIDTH-1:0];
+
+\SV
+
+endmodule