Changed modexp core to use explicit exponent length to allow removal of padding of exponent and improving performance. Updated testbenches to match the changed lengths inside the device under test.

3 files changed, 66 insertions, 13 deletions

diff --git a/src/rtl/modexp_core.v b/src/rtl/modexp_core.v
index 45d1aa9..c1a88d1 100644
--- a/src/rtl/modexp_core.v
+++ b/src/rtl/modexp_core.v
@@ -236,7 +236,8 @@ module modexp_core #(parameter OPW = 32, parameter ADW = 8)
   reg           residue_valid_new;
   reg           residue_valid_int_validated;
 
-  wire [7 : 0]  length_m1;
+  wire [7 : 0]  modulus_length_m1;
+  wire [7 : 0]  exponent_length_m1;
 
 
   //----------------------------------------------------------------
@@ -245,7 +246,8 @@ module modexp_core #(parameter OPW = 32, parameter ADW = 8)
   assign ready  = ready_reg;
   assign cycles = {cycle_ctr_high_reg, cycle_ctr_low_reg};
 
-  assign length_m1 = modulus_length - 8'h1;
+  assign modulus_length_m1  = modulus_length - 8'h1;
+  assign exponent_length_m1 = exponent_length - 8'h1;
 
 
   //----------------------------------------------------------------
@@ -495,10 +497,10 @@ module modexp_core #(parameter OPW = 32, parameter ADW = 8)
       one_new   = 32'h00000000;
       b_one_new = 32'h00000000;
 
-      if (montprod_opa_addr == length_m1)
+      if (montprod_opa_addr == modulus_length_m1)
         one_new = 32'h00000001;
 
-      if (montprod_opb_addr == length_m1)
+      if (montprod_opb_addr == modulus_length_m1)
         b_one_new = 32'h00000001;
     end
 
@@ -644,7 +646,7 @@ module modexp_core #(parameter OPW = 32, parameter ADW = 8)
       loop_counter_new = 13'b0;
       loop_counter_we  = 1'b0;
 
-      if (loop_counter_reg == {length_m1, 5'b11111})
+      if (loop_counter_reg == {exponent_length_m1, 5'b11111})
         last_iteration = 1'b1;
       else
         last_iteration = 1'b0;
@@ -678,7 +680,7 @@ module modexp_core #(parameter OPW = 32, parameter ADW = 8)
     begin : exponent_process
       // Accessing new instead of reg - pick up update at
       // CTRL_ITERATE_NEW to remove a pipeline stall.
-      E_word_index  = length_m1 - loop_counter_new[ 12 : 5 ];
+      E_word_index  = exponent_length_m1 - loop_counter_new[ 12 : 5 ];
 
       E_bit_index   = loop_counter_reg[ 04 : 0 ];
 
diff --git a/src/tb/tb_modexp.v b/src/tb/tb_modexp.v
index fe22662..363b4ed 100644
--- a/src/tb/tb_modexp.v
+++ b/src/tb/tb_modexp.v
@@ -256,8 +256,8 @@ module tb_modexp();
                dut.core_inst.ready_reg, dut.start_reg, dut.start_new);
       $display("residue_valid = 0x%01x", dut.core_inst.residue_valid_reg);
       $display("loop_counter_reg = 0x%08x", dut.core_inst.loop_counter_reg);
-      $display("exponent_length_reg = 0x%02x, modulus_length_reg = 0x%02x length_m1 = 0x%02x",
-               dut.exponent_length_reg, dut.modulus_length_reg, dut.core_inst.length_m1);
+      $display("exponent_length_reg = 0x%02x exponent_length_m1 = 0x%02x modulus_length_reg = 0x%02x modulus_length_m1 = 0x%02x",
+               dut.exponent_length_reg,  dut.core_inst.exponent_length_m1, dut.modulus_length_reg, dut.core_inst.modulus_length_m1);
       $display("ctrl_reg = 0x%04x", dut.core_inst.modexp_ctrl_reg);
       $display("");
     end
@@ -885,6 +885,56 @@ module tb_modexp();
 
 
   //----------------------------------------------------------------
+  // e65537_64bit_modulus_elength()
+  //----------------------------------------------------------------
+  task e65537_64bit_modulus_elength();
+    reg [31 : 0] read_data;
+    begin
+      success = 32'h1;
+      tc_ctr = tc_ctr + 1;
+      $display("Test with e = 65537 and 64 bit modulus, explicit exponent length.");
+
+      write_word({GENERAL_PREFIX, ADDR_EXPONENT_PTR_RST}, 32'h00000000);
+      write_word({GENERAL_PREFIX, ADDR_EXPONENT_DATA}, 32'h00010001);
+
+      write_word({GENERAL_PREFIX, ADDR_MODULUS_PTR_RST}, 32'h00000000);
+      write_word({GENERAL_PREFIX, ADDR_MODULUS_DATA}, 32'h00000000);
+      write_word({GENERAL_PREFIX, ADDR_MODULUS_DATA}, 32'hf077656f);
+      write_word({GENERAL_PREFIX, ADDR_MODULUS_DATA}, 32'h3bf9e69b);
+
+      write_word({GENERAL_PREFIX, ADDR_MESSAGE_PTR_RST}, 32'h00000000);
+      write_word({GENERAL_PREFIX, ADDR_MESSAGE_DATA}, 32'h00000000);
+      write_word({GENERAL_PREFIX, ADDR_MESSAGE_DATA}, 32'hb6684dc3);
+      write_word({GENERAL_PREFIX, ADDR_MESSAGE_DATA}, 32'h79a5824b);
+
+      write_word({GENERAL_PREFIX, ADDR_EXPONENT_LENGTH}, 32'h00000001);
+      write_word({GENERAL_PREFIX, ADDR_MODULUS_LENGTH}, 32'h00000003);
+
+      start_test_cycle_ctr();
+
+      // Start processing and wait for ready.
+      write_word({GENERAL_PREFIX, ADDR_CTRL}, 32'h00000001);
+      wait_ready();
+
+      stop_test_cycle_ctr();
+
+      write_word({GENERAL_PREFIX, ADDR_RESULT_PTR_RST}, 32'h00000000);
+      read_word({GENERAL_PREFIX, ADDR_RESULT_DATA}); read_data = tb_read_data; success = success & assertEquals(32'h00000000, read_data);
+      read_word({GENERAL_PREFIX, ADDR_RESULT_DATA}); read_data = tb_read_data; success = success & assertEquals(32'h132d8e17, read_data);
+      read_word({GENERAL_PREFIX, ADDR_RESULT_DATA}); read_data = tb_read_data; success = success & assertEquals(32'hdd4d85a4, read_data);
+
+      if (success !== 1)
+        begin
+          $display("*** ERROR: e65537_64bit_modulus with explicit elength was NOT successful.");
+          error_ctr = error_ctr + 1;
+        end
+      else
+        $display("*** e65537_64bit_modulus success.");
+    end
+  endtask // e65537_64bit_modulus_elength
+
+
+  //----------------------------------------------------------------
   // e65537_128bit_modulus()
   //----------------------------------------------------------------
   task e65537_128bit_modulus();
@@ -1398,10 +1448,11 @@ module tb_modexp();
 //      tc1();
 //      tc2();
 //      tc3();
-      autogenerated_BASIC_33bit();
-      autogenerated_BASIC_128bit();
+//      autogenerated_BASIC_33bit();
+//      autogenerated_BASIC_128bit();
       e65537_64bit_modulus();
-//      e65537_128bit_modulus();
+      e65537_64bit_modulus_elength();
+  //      e65537_128bit_modulus();
 //      e65537_256bit_modulus();
 
 //      rob_dec_1024();
diff --git a/src/tb/tb_modexp_autogenerated.v b/src/tb/tb_modexp_autogenerated.v
index 1eb80d5..0bb9432 100644
--- a/src/tb/tb_modexp_autogenerated.v
+++ b/src/tb/tb_modexp_autogenerated.v
@@ -174,8 +174,8 @@ module tb_modexp_autogenerated();
                dut.core_inst.ready_reg, dut.start_reg, dut.start_new);
       $display("residue_valid = 0x%01x", dut.core_inst.residue_valid_reg);
       $display("loop_counter_reg = 0x%08x", dut.core_inst.loop_counter_reg);
-      $display("exponent_length_reg = 0x%02x, modulus_length_reg = 0x%02x length_m1 = 0x%02x",
-               dut.exponent_length_reg, dut.modulus_length_reg, dut.core_inst.length_m1);
+      $display("exponent_length_reg = 0x%02x, modulus_length_reg = 0x%02x modulus_length_m1 = 0x%02x",
+               dut.exponent_length_reg, dut.modulus_length_reg, dut.core_inst.modulus_length_m1);
       $display("ctrl_reg = 0x%04x", dut.core_inst.modexp_ctrl_reg);
       $display("");
     end