//======================================================================
//
// rosc_entropy.v
// --------------
// Top level wrapper for the ring oscillator entropy core.
//
//
// 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 rosc_entropy(
input wire clk,
input wire reset_n,
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
);
//----------------------------------------------------------------
// Parameters.
//----------------------------------------------------------------
parameter ADDR_CTRL = 8'h00;
parameter CTRL_ENABLE_BIT = 0;
parameter ADDR_STATUS = 8'h01;
parameter STATUS_ENTROPY_VALID_BIT = 0;
parameter ADDR_OP_A = 8'h08;
parameter ADDR_OP_B = 8'h09;
parameter ADDR_ENTROPY = 8'h10;
parameter ADDR_RAW = 8'h20;
parameter ADDR_ROSC_OUTPUTS = 8'h21;
parameter DEFAULT_OP_A = 32'haaaaaaaa;
parameter DEFAULT_OP_B = ~DEFAULT_OP_A;
//----------------------------------------------------------------
// Registers including update variables and write enable.
//----------------------------------------------------------------
reg enable_reg;
reg enable_new;
reg enable_we;
reg [31 : 0] op_a_reg;
reg [31 : 0] op_a_new;
reg op_a_we;
reg [31 : 0] op_b_reg;
reg [31 : 0] op_b_new;
reg op_b_we;
//----------------------------------------------------------------
// Wires.
//----------------------------------------------------------------
wire [31 : 0] raw_entropy;
wire [31 : 0] rosc_outputs;
wire [31 : 0] internal_entropy_data;
wire internal_entropy_valid;
wire internal_entropy_ack;
reg api_entropy_ack;
reg [31 : 0] tmp_read_data;
reg tmp_error;
//----------------------------------------------------------------
// Concurrent connectivity for ports etc.
//----------------------------------------------------------------
assign read_data = tmp_read_data;
assign error = tmp_error;
assign security_error = 0;
assign entropy_enabled = enable_reg;
assign entropy_data = internal_entropy_data;
assign entropy_valid = internal_entropy_valid;
assign internal_entropy_ack = api_entropy_ack | entropy_ack;
//----------------------------------------------------------------
// module instantiations.
//----------------------------------------------------------------
rosc_entropy_core core(
.clk(clk),
.reset_n(reset_n),
.en(enable_reg),
.opa(op_a_reg),
.opb(op_b_reg),
.raw_entropy(raw_entropy),
.rosc_outputs(rosc_outputs),
.entropy_data(internal_entropy_data),
.entropy_valid(internal_entropy_valid),
.entropy_ack(internal_entropy_ack),
.debug(debug),
.debug_update(debug_update)
);
//----------------------------------------------------------------
// reg_update
//
// Update functionality for all registers in the core.
// All registers are positive edge triggered with asynchronous
// active low reset.
//----------------------------------------------------------------
always @ (posedge clk or negedge reset_n)
begin
if (!reset_n)
begin
enable_reg <= 1;
op_a_reg <= DEFAULT_OP_A;
op_b_reg <= DEFAULT_OP_B;
end
else
begin
if (enable_we)
begin
enable_reg <= enable_new;
end
if (op_a_we)
begin
op_a_reg <= op_a_new;
end
if (op_b_we)
begin
op_b_reg <= op_b_new;
end
end
end // reg_update
//----------------------------------------------------------------
// api_logic
//
// Implementation of the api logic. If cs is enabled will either
// try to write to or read from the internal registers.
//----------------------------------------------------------------
always @*
begin : api_logic
enable_new = 0;
enable_we = 0;
op_a_new = 0;
op_a_we = 0;
op_b_new = 0;
op_b_we = 0;
api_entropy_ack = 0;
tmp_read_data = 32'h00000000;
tmp_error = 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
ADDR_OP_A:
begin
op_a_new = write_data;
op_a_we = 1;
end
ADDR_OP_B:
begin
op_b_new = write_data;
op_b_we = 1;
end
default:
begin
tmp_error = 1;
end
endcase // case (address)
end
else
begin
case (address)
ADDR_CTRL:
begin
tmp_read_data[CTRL_ENABLE_BIT] = enable_reg;
end
ADDR_STATUS:
begin
tmp_read_data[STATUS_ENTROPY_VALID_BIT] = internal_entropy_valid;
end
ADDR_OP_A:
begin
tmp_read_data = op_a_reg;
end
ADDR_OP_B:
begin
tmp_read_data = op_b_reg;
end
ADDR_ENTROPY:
begin
tmp_read_data = entropy_data;
api_entropy_ack = 1;
end
ADDR_RAW:
begin
tmp_read_data = raw_entropy;
end
ADDR_ROSC_OUTPUTS:
begin
tmp_read_data = rosc_outputs;
end
default:
begin
tmp_error = 1;
end
endcase // case (address)
end
end
end
endmodule // rosc_entropy_core
//======================================================================
// EOF rosc_entropy_core.v
//======================================================================
