//======================================================================
//
// montprod.v
// ---------
// Montgomery product calculator for the modular exponentiantion core.
//
// parameter OPW is operand word width in bits.
// parameter ADW is address width in bits.
//
//
// Author: Peter Magnusson, Joachim Strombergson
// Copyright (c) 2015, 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 montprod #(parameter OPW = 32, parameter ADW = 8)
(
input wire clk,
input wire reset_n,
input wire calculate,
output wire ready,
input [(ADW - 1) : 0] length,
output wire [(ADW - 1) : 0] opa_addr,
input wire [(OPW - 1) : 0] opa_data,
output wire [(ADW - 1) : 0] opb_addr,
input wire [(OPW - 1) : 0] opb_data,
output wire [(ADW - 1) : 0] opm_addr,
input wire [(OPW - 1) : 0] opm_data,
output wire [(ADW - 1) : 0] result_addr,
output wire [(OPW - 1) : 0] result_data,
output wire result_we
);
//----------------------------------------------------------------
// Internal constant and parameter definitions.
//----------------------------------------------------------------
localparam CTRL_IDLE = 4'h0;
localparam CTRL_LOOP_ITER = 4'h1;
localparam CTRL_LOOP_BQ = 4'h2;
localparam CTRL_CALC_ADD = 4'h3;
localparam CTRL_STALLPIPE_ADD = 4'h4;
localparam CTRL_CALC_SDIV2 = 4'h5;
localparam CTRL_STALLPIPE_SDIV2 = 4'h6;
localparam CTRL_L_STALLPIPE_ES = 4'h7;
localparam CTRL_EMIT_S = 4'h8;
localparam SMUX_ZERO = 2'h0;
localparam SMUX_ADD = 2'h1;
localparam SMUX_SHR = 2'h2;
//----------------------------------------------------------------
// Registers including update variables and write enable.
//----------------------------------------------------------------
reg ready_reg;
reg ready_new;
reg ready_we;
reg [3 : 0] montprod_ctrl_reg;
reg [3 : 0] montprod_ctrl_new;
reg montprod_ctrl_we;
reg [1 : 0] s_mux_new;
reg [1 : 0] s_mux_reg;
reg s_mem_we_reg;
reg s_mem_we_new;
reg [(ADW - 1) : 0] s_mem_read_addr_reg;
reg [(ADW - 1) : 0] s_mem_write_addr_reg;
reg q_new;
reg q_reg;
reg b_new;
reg b_reg;
reg bq_we;
reg [12 : 0] loop_ctr_reg;
reg [12 : 0] loop_ctr_new;
reg loop_ctr_we;
reg loop_ctr_set;
reg loop_ctr_dec;
reg [(13 - ADW - 1) : 0] b_bit_index_reg;
reg [(13 - ADW - 1) : 0] b_bit_index_new;
reg b_bit_index_we;
reg [(ADW - 1) : 0] word_index_reg;
reg [(ADW - 1) : 0] word_index_new;
reg word_index_we;
reg [(ADW - 1) : 0] word_index_prev_reg;
reg reset_word_index_lsw;
reg reset_word_index_msw;
reg inc_word_index;
reg dec_word_index;
reg add_carry_in_sa_reg;
reg add_carry_in_sa_new;
reg add_carry_in_sm_reg;
reg add_carry_in_sm_new;
reg shr_carry_in_reg;
reg shr_carry_in_new;
reg first_iteration_reg;
reg first_iteration_new;
reg first_iteration_we;
//----------------------------------------------------------------
// Wires.
//----------------------------------------------------------------
wire [(OPW - 1) : 0] add_result_sa;
wire add_carry_out_sa;
wire [(OPW - 1) : 0] add_result_sm;
wire add_carry_out_sm;
reg [(ADW - 1) : 0] b_word_index; //loop counter as a word index
reg [(OPW - 1) : 0] shr_data_in;
wire shr_carry_out;
wire [(OPW - 1) : 0] shr_data_out;
reg [(ADW - 1) : 0] tmp_opa_addr;
reg tmp_result_we;
reg [(ADW - 1) : 0] s_mem_read_addr;
wire [(OPW - 1) : 0] s_mem_read_data;
reg [(ADW - 1) : 0] s_mem_write_addr;
reg [(OPW - 1) : 0] s_mem_write_data;
reg [(OPW - 1) : 0] sa_adder_data_in;
reg [(OPW - 1) : 0] muxed_s_mem_read_data;
wire [(ADW - 1) : 0] length_m1;
// Temporary debug wires.
reg b_js;
reg pr_tt;
reg s_mem_we;
//----------------------------------------------------------------
// Concurrent connectivity for ports etc.
//----------------------------------------------------------------
assign length_m1 = length - 1'b1;
assign opa_addr = tmp_opa_addr;
assign opb_addr = b_word_index;
assign opm_addr = word_index_reg;
assign result_addr = word_index_prev_reg;
assign result_data = s_mem_read_data;
assign result_we = tmp_result_we;
assign ready = ready_reg;
//----------------------------------------------------------------
// Instantions
//----------------------------------------------------------------
blockmem1r1w #(.OPW(OPW), .ADW(ADW)) s_mem(
.clk(clk),
.read_addr(s_mem_read_addr),
.read_data(s_mem_read_data),
.wr(s_mem_we_reg | s_mem_we),
.write_addr(s_mem_write_addr),
.write_data(s_mem_write_data)
);
adder #(.OPW(OPW)) s_adder_sm(
.a(muxed_s_mem_read_data),
.b(opm_data),
.carry_in(add_carry_in_sm_reg),
.sum(add_result_sm),
.carry_out(add_carry_out_sm)
);
adder #(.OPW(OPW)) s_adder_sa(
.a(sa_adder_data_in),
.b(opa_data),
.carry_in(add_carry_in_sa_reg),
.sum(add_result_sa),
.carry_out(add_carry_out_sa)
);
shr #(.OPW(OPW)) shifter(
.a(s_mem_read_data),
.carry_in(shr_carry_in_reg),
.adiv2(shr_data_out),
.carry_out(shr_carry_out)
);
//----------------------------------------------------------------
// reg_update
//
// Update functionality for all registers in the core.
// All registers are positive edge triggered with asynchronous
// active low reset. All registers have write enable.
//----------------------------------------------------------------
always @ (posedge clk or negedge reset_n)
begin : reg_update
if (!reset_n)
begin
ready_reg <= 1'b1;
loop_ctr_reg <= 13'h0;
word_index_reg <= {ADW{1'b0}};
word_index_prev_reg <= {ADW{1'b0}};
add_carry_in_sa_reg <= 1'b0;
add_carry_in_sm_reg <= 1'b0;
shr_carry_in_reg <= 1'b0;
b_reg <= 1'b0;
q_reg <= 1'b0;
s_mux_reg <= SMUX_ZERO;
s_mem_we_reg <= 1'b0;
s_mem_read_addr_reg <= {ADW{1'b0}};
b_bit_index_reg <= {(13 - ADW){1'b0}};
first_iteration_reg <= 1'b0;
montprod_ctrl_reg <= CTRL_IDLE;
end
else
begin
s_mem_read_addr_reg <= s_mem_read_addr;
s_mem_we_reg <= s_mem_we_new;
s_mux_reg <= s_mux_new;
word_index_prev_reg <= word_index_reg;
shr_carry_in_reg <= shr_carry_in_new;
add_carry_in_sa_reg <= add_carry_in_sa_new;
add_carry_in_sm_reg <= add_carry_in_sm_new;
if (word_index_we)
word_index_reg <= word_index_new;
if (first_iteration_we)
first_iteration_reg <= first_iteration_new;
if (b_bit_index_we)
b_bit_index_reg <= b_bit_index_new;
if (bq_we)
begin
b_reg <= b_new;
q_reg <= q_new;
end
if (ready_we)
ready_reg <= ready_new;
if (loop_ctr_we)
loop_ctr_reg <= loop_ctr_new;
if (montprod_ctrl_we)
begin
montprod_ctrl_reg <= montprod_ctrl_new;
end
end
end // reg_update
//----------------------------------------------------------------
// s_logic
//
// Logic to calculate S memory updates including address
// and write enable. This is the main montprod datapath.
//----------------------------------------------------------------
always @*
begin : s_logic
shr_carry_in_new = 1'b0;
muxed_s_mem_read_data = {OPW{1'b0}};
sa_adder_data_in = {OPW{1'b0}};
add_carry_in_sa_new = 1'b0;
add_carry_in_sm_new = 1'b0;
s_mem_read_addr = word_index_reg;
s_mem_write_addr = s_mem_read_addr_reg;
s_mem_write_data = {OPW{1'b0}};
s_mem_we_new = 1'b0;
s_mem_we = 1'b0;
case (montprod_ctrl_reg)
CTRL_LOOP_ITER:
begin
s_mem_read_addr = length_m1;
end
CTRL_LOOP_BQ:
begin
s_mem_read_addr = length_m1;
end
CTRL_CALC_ADD:
begin
//s = (s + q*M + b*A) >>> 1;, if(b==1) S+= A. Takes (1..length) cycles.
s_mem_we_new = b_reg | q_reg | first_iteration_reg;
end
CTRL_CALC_SDIV2:
begin
//s = (s + q*M + b*A) >>> 1; s>>=1. Takes (1..length) cycles.
s_mem_we_new = 1'b1;
end
default:
begin
end
endcase
case (s_mux_reg)
SMUX_ADD:
begin
s_mem_we = b_reg | q_reg | first_iteration_reg;
if (first_iteration_reg)
muxed_s_mem_read_data = {OPW{1'b0}};
else
muxed_s_mem_read_data = s_mem_read_data;
if (q_reg)
sa_adder_data_in = add_result_sm;
else
sa_adder_data_in = muxed_s_mem_read_data;
if (b_reg)
s_mem_write_data = add_result_sa;
else if (q_reg)
s_mem_write_data = add_result_sm;
else if (first_iteration_reg)
s_mem_write_data = {OPW{1'b0}};
else
s_mem_write_data = s_mem_read_data;
add_carry_in_sa_new = add_carry_out_sa;
add_carry_in_sm_new = add_carry_out_sm;
end
SMUX_SHR:
begin
s_mem_we = 1'b1;
shr_data_in = s_mem_read_data;
s_mem_write_data = shr_data_out;
shr_carry_in_new = shr_carry_out;
end
default:
begin
end
endcase
end // s_logic
//----------------------------------------------------------------
// bq
//
// Extract b and q bits.
// b: current bit of B used.
// q = (s - b * A) & 1
// update the b bit and word indices based on loop counter.
//----------------------------------------------------------------
always @*
begin : bq
b_new = opb_data[b_bit_index_reg];
if (first_iteration_reg)
q_new = 1'b0 ^ (opa_data[0] & b_new);
else
q_new = s_mem_read_data[0] ^ (opa_data[0] & b_new);
b_bit_index_new = (2**(13 - ADW) - 1) - loop_ctr_reg[(13 - ADW - 1) : 0];
b_word_index = loop_ctr_reg[12 : (13 - ADW)];
end // bq
//----------------------------------------------------------------
// word_index
//
// Logic that implements the word index used to drive
// addresses for operands.
//----------------------------------------------------------------
always @*
begin : word_index
word_index_new = {ADW{1'b0}};
word_index_we = 1'b0;
if (reset_word_index_lsw)
begin
word_index_new = length_m1;
word_index_we = 1'b1;
end
if (reset_word_index_msw)
begin
word_index_new = {ADW{1'b0}};
word_index_we = 1'b1;
end
if (inc_word_index)
begin
word_index_new = word_index_reg + 1'b1;
word_index_we = 1'b1;
end
if (dec_word_index)
begin
word_index_new = word_index_reg - 1'b1;
word_index_we = 1'b1;
end
end // word_index
//----------------------------------------------------------------
// loop_ctr
// Logic for updating the loop counter.
//----------------------------------------------------------------
always @*
begin : loop_ctr
loop_ctr_new = 13'h0;
loop_ctr_we = 1'b0;
if (loop_ctr_set)
begin
loop_ctr_new = {length, {(13 - ADW){1'b0}}} - 1'b1;
loop_ctr_we = 1'b1;
end
if (loop_ctr_dec)
begin
loop_ctr_new = loop_ctr_reg - 1'b1;
loop_ctr_we = 1'b1;
end
end
//----------------------------------------------------------------
// montprod_ctrl
//
// Control FSM for the montgomery product calculator.
//----------------------------------------------------------------
always @*
begin : montprod_ctrl
ready_new = 1'b0;
ready_we = 1'b0;
loop_ctr_set = 1'b0;
loop_ctr_dec = 1'b0;
b_bit_index_we = 1'b0;
bq_we = 1'b0;
s_mux_new = SMUX_ZERO;
dec_word_index = 1'b0;
inc_word_index = 1'b0;
reset_word_index_lsw = 1'b0;
reset_word_index_msw = 1'b0;
first_iteration_new = 1'b0;
first_iteration_we = 1'b0;
tmp_opa_addr = word_index_reg;
tmp_result_we = 1'b0;
montprod_ctrl_new = CTRL_IDLE;
montprod_ctrl_we = 1'b0;
case (montprod_ctrl_reg)
CTRL_IDLE:
begin
if (calculate)
begin
first_iteration_new = 1'b1;
first_iteration_we = 1'b1;
ready_new = 1'b0;
ready_we = 1'b1;
reset_word_index_lsw = 1'b1;
loop_ctr_set = 1'b1;
montprod_ctrl_new = CTRL_LOOP_ITER;
montprod_ctrl_we = 1'b1;
end
end
//calculate q = (s - b * A) & 1;.
// Also abort loop if done.
CTRL_LOOP_ITER:
begin
tmp_opa_addr = length_m1;
b_bit_index_we = 1'b1;
montprod_ctrl_new = CTRL_LOOP_BQ;
montprod_ctrl_we = 1'b1;
end
CTRL_LOOP_BQ:
begin
reset_word_index_lsw = 1'b1;
bq_we = 1'b1;
montprod_ctrl_new = CTRL_CALC_ADD;
montprod_ctrl_we = 1'b1;
end
CTRL_CALC_ADD:
begin
s_mux_new = SMUX_ADD;
dec_word_index = 1'b1;
if (word_index_reg == 0)
begin
reset_word_index_lsw = 1'b1;
montprod_ctrl_new = CTRL_STALLPIPE_ADD;
montprod_ctrl_we = 1'b1;
end
end
CTRL_STALLPIPE_ADD:
begin
first_iteration_new = 1'b0;
first_iteration_we = 1'b1;
reset_word_index_msw = 1'b1;
montprod_ctrl_new = CTRL_CALC_SDIV2;
montprod_ctrl_we = 1'b1;
end
CTRL_CALC_SDIV2:
begin
s_mux_new = SMUX_SHR;
inc_word_index = 1'b1;
if (word_index_reg == length_m1)
begin
montprod_ctrl_new = CTRL_STALLPIPE_SDIV2;
montprod_ctrl_we = 1'b1;
end
end
CTRL_STALLPIPE_SDIV2:
begin
loop_ctr_dec = 1'b1;
montprod_ctrl_new = CTRL_LOOP_ITER;
montprod_ctrl_we = 1'b1;
reset_word_index_lsw = 1'b1;
if (loop_ctr_reg == 0)
begin
montprod_ctrl_new = CTRL_L_STALLPIPE_ES;
montprod_ctrl_we = 1'b1;
end
end
CTRL_L_STALLPIPE_ES:
begin
montprod_ctrl_new = CTRL_EMIT_S;
montprod_ctrl_we = 1'b1;
end
CTRL_EMIT_S:
begin
dec_word_index = 1'b1;
tmp_result_we = 1'b1;
if (word_index_prev_reg == 0)
begin
ready_new = 1'b1;
ready_we = 1'b1;
montprod_ctrl_new = CTRL_IDLE;
montprod_ctrl_we = 1'b1;
end
end
default:
begin
end
endcase // case (montprod_ctrl_reg)
end // montprod_ctrl
endmodule // montprod
//======================================================================
// EOF montprod.v
//======================================================================