//======================================================================
//
// avalanche_entropy.v
// -------------------
// Top level wrapper of the entropy provider core based on an external
// avalanche noise based source. (or any other source that can
// toggle a single bit input).
//
// Currently the design consists of a free running counter. At every
// positive flank detected the LSB of the counter is pushed into
// a 32bit shift register.
//
//
// 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 avalanche_entropy(
input wire clk,
input wire reset_n,
input wire noise,
input wire cs,
input wire we,
input wire [7 : 0] address,
input wire [31 : 0] write_data,
output wire [31 : 0] read_data,
output wire error,
input wire discard,
input wire test_mode,
output wire security_error,
output wire entropy_enabled,
output wire [31 : 0] entropy_data,
output wire entropy_valid,
input wire entropy_ack,
output wire [7 : 0] debug,
input wire debug_update
);
//----------------------------------------------------------------
// Internal constant and parameter definitions.
//----------------------------------------------------------------
localparam ADDR_NAME0 = 8'h00;
localparam ADDR_NAME1 = 8'h01;
localparam ADDR_VERSION = 8'h02;
localparam ADDR_CTRL = 8'h08;
localparam CTRL_ENABLE_BIT = 0;
localparam ADDR_STATUS = 8'h09;
localparam STATUS_VALID_BIT = 1;
localparam ADDR_ENTROPY = 8'h20;
localparam ADDR_DELTA = 8'h30;
localparam CORE_NAME0 = 32'h6578746e; // "extn"
localparam CORE_NAME1 = 32'h6f697365; // "oise"
localparam CORE_VERSION = 32'h302e3130; // "0.10"
//----------------------------------------------------------------
// Registers including update variables and write enable.
//----------------------------------------------------------------
reg enable_reg;
reg enable_new;
reg enable_we;
//----------------------------------------------------------------
// Wires.
//----------------------------------------------------------------
reg [31 : 0] tmp_read_data;
reg tmp_error;
wire [31 : 0] delta;
//----------------------------------------------------------------
// Concurrent connectivity for ports etc.
//----------------------------------------------------------------
assign read_data = tmp_read_data;
assign error = tmp_error;
assign security_error = 0;
//----------------------------------------------------------------
// Core instantiation.
//----------------------------------------------------------------
avalanche_entropy_core core(
.clk(clk),
.reset_n(reset_n),
.noise(noise),
.enable(enable_reg),
.entropy_data(entropy_data),
.entropy_enabled(entropy_enabled),
.entropy_valid(entropy_valid),
.entropy_ack(entropy_ack),
.delta(delta),
.debug(debug),
.debug_update(debug_update)
);
//----------------------------------------------------------------
// reg_update
//----------------------------------------------------------------
always @ (posedge clk or negedge reset_n)
begin
if (!reset_n)
begin
enable_reg <= 1'h1;
end
else
begin
if (enable_we)
enable_reg <= enable_new;
end
end // reg_update
//----------------------------------------------------------------
// api_logic
//----------------------------------------------------------------
always @*
begin : api_logic
tmp_read_data = 32'h00000000;
tmp_error = 1'b0;
enable_new = 0;
enable_we = 0;
if (cs)
begin
if (we)
begin
case (address)
// Write operations.
ADDR_CTRL:
begin
enable_new = write_data[CTRL_ENABLE_BIT];
enable_we = 1;
end
default:
begin
tmp_error = 1;
end
endcase // case (address)
end // if (we)
else
begin
case (address)
ADDR_NAME0:
begin
tmp_read_data = CORE_NAME0;
end
ADDR_NAME1:
begin
tmp_read_data = CORE_NAME1;
end
ADDR_VERSION:
begin
tmp_read_data = CORE_VERSION;
end
ADDR_CTRL:
begin
tmp_read_data[CTRL_ENABLE_BIT] = enable_reg;
end
ADDR_STATUS:
begin
tmp_read_data[STATUS_VALID_BIT] = entropy_valid;
end
ADDR_ENTROPY:
begin
tmp_read_data = entropy_data;
end
ADDR_DELTA:
begin
tmp_read_data = delta;
end
default:
begin
tmp_error = 1;
end
endcase // case (address)
end // else: !if(we)
end // if (cs)
end // api_logic
endmodule // avalanche_entropy
//======================================================================
// EOF avalanche_entropy.v
//======================================================================
