LFSR

src/lfsr/lfsr_galois.veryl

@@ -0,0 +1,112 @@
+pub module lfsr_galois #(
+    /// Size of the LFSR in bits
+    parameter  SIZE  : u32  = 64         ,
+    localparam tapvec: type = logic<SIZE>,
+    /// Bit-vector representing the taps of the LFSR.
+    /// Default values provided for `SIZE` in range [2, 64]
+    parameter TAPVEC: tapvec = case SIZE {
+        2      : 2'h3,
+        3      : 3'h5,
+        4      : 4'h9,
+        5      : 5'h12,
+        6      : 6'h21,
+        7      : 7'h41,
+        8      : 8'h8e,
+        9      : 9'h108,
+        10     : 10'h204,
+        11     : 11'h402,
+        12     : 12'h829,
+        13     : 13'h100d,
+        14     : 14'h2015,
+        15     : 15'h4001,
+        16     : 16'h8016,
+        17     : 17'h10004,
+        18     : 18'h20013,
+        19     : 19'h40013,
+        20     : 20'h80004,
+        21     : 21'h100002,
+        22     : 22'h200001,
+        23     : 23'h400010,
+        24     : 24'h80000d,
+        25     : 25'h1000004,
+        26     : 26'h2000023,
+        27     : 27'h4000013,
+        28     : 28'h8000004,
+        29     : 29'h10000002,
+        30     : 30'h20000029,
+        31     : 31'h40000004,
+        32     : 32'h80000057,
+        33     : 33'h100000029,
+        34     : 34'h200000073,
+        35     : 35'h400000002,
+        36     : 36'h80000003b,
+        37     : 37'h100000001f,
+        38     : 38'h2000000031,
+        39     : 39'h4000000008,
+        40     : 40'h800000001c,
+        41     : 41'h10000000004,
+        42     : 42'h2000000001f,
+        43     : 43'h4000000002c,
+        44     : 44'h80000000032,
+        45     : 45'h10000000000d,
+        46     : 46'h200000000097,
+        47     : 47'h400000000010,
+        48     : 48'h80000000005b,
+        49     : 49'h1000000000038,
+        50     : 50'h200000000000e,
+        51     : 51'h4000000000025,
+        52     : 52'h8000000000004,
+        53     : 53'h10000000000023,
+        54     : 54'h2000000000003e,
+        55     : 55'h40000000000023,
+        56     : 56'h8000000000004a,
+        57     : 57'h100000000000016,
+        58     : 58'h200000000000031,
+        59     : 59'h40000000000003d,
+        60     : 60'h800000000000001,
+        61     : 61'h1000000000000013,
+        62     : 62'h2000000000000034,
+        63     : 63'h4000000000000001,
+        64     : 64'h800000000000000d,
+        default       : '0,
+    },
+
+) (
+    /// Clock
+    i_clk: input logic,
+    /// Enable - LFSR shifts only when enabled.  Active high.
+    i_en: input logic,
+    /// Flag to set value of LFSR.  Active High.
+    i_set: input logic,
+    /// Value which LFSR is set to when `i_set` is set.
+    i_setval: input logic<SIZE>,
+    /// LFSR value.
+    o_val: output logic<SIZE>,
+) {
+
+    var val_next: logic<SIZE>;
+
+    assign val_next[SIZE - 1] = o_val[0];
+    for i in 0..(SIZE - 1) :g_taps {
+        localparam k: u32 = SIZE - 2 - i;
+        if TAPVEC[k] :g_tap {
+            assign val_next[k] = if i_set {
+                i_setval[k]
+            } else {
+                o_val[k + 1] ^ o_val[0]
+            };
+        } else :g_notap {
+            assign val_next[k] = if i_set {
+                i_setval[k]
+            } else {
+                o_val[k + 1]
+            };
+        }
+    }
+
+    always_ff (i_clk) {
+        if i_en {
+            o_val = val_next;
+        }
+    }
+}

testbench/lfsr_galois_bench.sv

@@ -0,0 +1,83 @@
+module testbench;
+    parameter MAXSIZE = 24;
+    parameter MINSIZE = 2;
+
+    logic [MAXSIZE-1:MINSIZE] done;
+    logic [MAXSIZE-1:MINSIZE] working;
+    logic i_clk;
+
+    for (genvar i = MINSIZE; i < MAXSIZE; ++i) begin
+        initial $display ("Spawning LFSR of Size %d", i);
+        lfsr_galois_bench #(.SIZE(i)) u_lfsr(.i_clk, .done(done[i]), .working(working[i]));
+    end
+    default clocking
+      @(posedge i_clk);
+    endclocking
+
+    initial forever begin
+        ##4
+        if (&done) begin
+            if (|working) begin
+                $display("Finishing Simulations with \033[32m100%% Success\033[0m");
+            end else begin
+                $display("Finishing Simulations with \033[31mErrors\033[0m");
+            end
+            $finish;
+        end
+    end
+
+  initial begin
+    i_clk = 1'b0;
+    forever #5 i_clk = ~i_clk;
+  end
+endmodule
+
+module lfsr_galois_bench #(parameter SIZE=64) (input i_clk, output logic done, output logic working);
+  logic [SIZE:0] limit;
+
+
+  logic i_en, i_set;
+  logic [SIZE-1:0] i_setval;
+  logic [SIZE-1:0] o_val;
+
+  std_lfsr_galois #(.SIZE(SIZE)) dut (.*);
+
+
+  default clocking
+    @(posedge i_clk);
+  endclocking
+
+
+  initial begin
+    int outvecs [logic[SIZE-1:0]];
+    working = 1'b1;
+    $display("Begining LFSR of Size %d", SIZE);
+    done = 1'b0;
+    i_en = 1'b1;
+    i_set = 1'b1;
+    i_setval = 16'h0001;
+
+    ##2;
+
+    i_set = 1'b0;
+    limit = '1;
+    limit[0] = 1'b0; 
+    limit[SIZE] = 1'b0;
+
+    for (int i = 0; i < limit; i += 1) begin
+      ##1;
+      assert(0 == outvecs.exists(o_val));
+      working &= !outvecs.exists(o_val);
+      outvecs[o_val] = 1'b1;
+    end
+
+    done = 1'b1;
+
+    if (working) 
+        $display("Succesfully Ending LFSR of Size %0d", SIZE);
+    else
+        $display("Failure Detecing in LFSR of size %0d", SIZE);
+
+  end
+
+endmodule