//======================================================================
//
// montprod.v
// ---------
// Montgomery product calculator for the modular exponentiantion core.
//
//
// 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(
input wire clk,
input wire reset_n,
input wire calculate,
output wire ready,
input [7 : 0] length,
output wire [7 : 0] opa_addr,
input wire [31 : 0] opa_data,
output wire [7 : 0] opb_addr,
input wire [31 : 0] opb_data,
output wire [7 : 0] opm_addr,
input wire [31 : 0] opm_data,
output wire [7 : 0] result_addr,
output wire [31 : 0] result_data,
output wire result_we
);
//----------------------------------------------------------------
// Internal constant and parameter definitions.
//----------------------------------------------------------------
localparam DEBUG = 0;
localparam CTRL_IDLE = 4'h0;
localparam CTRL_INIT_S = 4'h1;
localparam CTRL_LOOP_INIT = 4'h2;
localparam CTRL_LOOP_ITER = 4'h3;
localparam CTRL_LOOP_BQ = 4'h4;
localparam CTRL_L_CALC_SM = 4'h5;
localparam CTRL_L_STALLPIPE_SM = 4'h6;
localparam CTRL_L_CALC_SA = 4'h7;
localparam CTRL_L_STALLPIPE_SA = 4'h8;
localparam CTRL_L_CALC_SDIV2 = 4'h9;
localparam CTRL_L_STALLPIPE_D2 = 4'hA;
localparam CTRL_L_STALLPIPE_ES = 4'hB;
localparam CTRL_EMIT_S = 4'hC;
localparam CTRL_DONE = 4'hD;
localparam SMUX_0 = 2'h0;
localparam SMUX_ADD_SM = 2'h1;
localparam SMUX_ADD_SA = 2'h2;
localparam SMUX_SHR = 2'h3;
//----------------------------------------------------------------
// Registers including update variables and write enable.
//----------------------------------------------------------------
reg [07 : 0] opa_addr_reg;
reg [07 : 0] opb_addr_reg;
reg [07 : 0] opm_addr_reg;
reg [07 : 0] result_addr_reg;
reg [31 : 0] result_data_reg;
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 [31 : 0] s_mem_new;
reg s_mem_we;
reg s_mem_we_new;
reg [07 : 0] s_mem_addr;
reg [07 : 0] s_mem_wr_addr;
wire [31 : 0] s_mem_read_data;
reg q; //q = (s - b * A) & 1
reg q_reg;
reg b; //b: bit of B
reg b_reg;
reg [12 : 0] loop_counter;
reg [12 : 0] loop_counter_new;
reg [12 : 0] loop_counter_dec;
reg [07 : 0] B_word_index; //loop counter as a word index
reg [04 : 0] B_bit_index; //loop counter as a bit index
reg [04 : 0] B_bit_index_reg; //loop counter as a bit index
reg [07 : 0] word_index; //register of what word is being read
reg [07 : 0] word_index_new; //calculation of what word to be read
reg [07 : 0] word_index_prev; //register of what word was read previously (result address to emit)
reg [07 : 0] length_m1;
reg add_carry_in_sa;
reg add_carry_new_sa;
reg add_carry_in_sm;
reg add_carry_new_sm;
reg shr_carry_in;
reg shr_carry_new;
reg reset_word_index_LSW;
reg reset_word_index_MSW;
//----------------------------------------------------------------
// Wires.
//----------------------------------------------------------------
reg tmp_result_we;
wire [31 : 0] add_result_sa;
wire add_carry_out_sa;
wire [31 : 0] add_result_sm;
wire add_carry_out_sm;
wire shr_carry_out;
wire [31 : 0] shr_adiv2;
//----------------------------------------------------------------
// Concurrent connectivity for ports etc.
//----------------------------------------------------------------
assign opa_addr = opa_addr_reg;
assign opb_addr = opb_addr_reg;
assign opm_addr = opm_addr_reg;
assign result_addr = result_addr_reg;
assign result_data = result_data_reg;
assign result_we = tmp_result_we;
assign ready = ready_reg;
//----------------------------------------------------------------
// Instantions
//----------------------------------------------------------------
blockmem1r1w s_mem(
.clk(clk),
.read_addr(s_mem_addr),
.read_data(s_mem_read_data),
.wr(s_mem_we),
.write_addr(s_mem_wr_addr),
.write_data(s_mem_new)
);
adder32 s_adder_sa(
.a(s_mem_read_data),
.b(opa_data),
.carry_in(add_carry_in_sa),
.sum(add_result_sa),
.carry_out(add_carry_out_sa)
);
adder32 s_adder_sm(
.a(s_mem_read_data),
.b(opm_data),
.carry_in(add_carry_in_sm),
.sum(add_result_sm),
.carry_out(add_carry_out_sm)
);
shr32 shifter(
.a( s_mem_read_data ),
.carry_in( shr_carry_in ),
.adiv2( shr_adiv2 ),
.carry_out( shr_carry_out )
);
always @*
begin : s_mux
case (s_mux_reg)
SMUX_0:
s_mem_new = 32'b0;
SMUX_ADD_SA:
s_mem_new = add_result_sa;
SMUX_ADD_SM:
s_mem_new = add_result_sm;
SMUX_SHR:
s_mem_new = shr_adiv2;
endcase
if (DEBUG)
$display("SMUX%x: %x", s_mux_reg, s_mem_new);
end
//----------------------------------------------------------------
// 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'b0;
loop_counter <= 13'h0;
word_index <= 8'h0;
word_index_prev <= 8'h0;
add_carry_in_sa <= 1'b0;
add_carry_in_sm <= 1'b0;
shr_carry_in <= 1'b0;
montprod_ctrl_reg <= CTRL_IDLE;
b_reg <= 1'b0;
q_reg <= 1'b0;
s_mux_reg <= SMUX_0;
s_mem_we <= 1'b0;
s_mem_wr_addr <= 8'h0;
B_bit_index_reg <= 5'h0;
end
else
begin
if (ready_we)
ready_reg <= ready_new;
if (montprod_ctrl_we)
begin
montprod_ctrl_reg <= montprod_ctrl_new;
end
s_mem_wr_addr <= s_mem_addr;
s_mem_we <= s_mem_we_new;
word_index <= word_index_new;
word_index_prev <= word_index;
loop_counter <= loop_counter_new;
shr_carry_in <= shr_carry_new;
add_carry_in_sa <= add_carry_new_sa;
add_carry_in_sm <= add_carry_new_sm;
B_bit_index_reg <= B_bit_index;
q_reg <= q;
b_reg <= b;
s_mux_reg <= s_mux_new;
end
end // reg_update
always @*
begin : bq_process
b = b_reg;
q = q_reg;
if (montprod_ctrl_reg == CTRL_LOOP_BQ)
begin
b = opb_data[ B_bit_index_reg ];
//opa_addr will point to length-1 to get A LSB.
//s_read_addr will point to length-1
q = s_mem_read_data[0] ^ (opa_data[0] & b);
if (DEBUG)
$display("s_mem_read_data: %x opa_data %x b %x q %x B_bit_index_reg %x", s_mem_read_data, opa_data, b, q, B_bit_index_reg);
end
end
//----------------------------------------------------------------
// Process for iterating the loop counter and setting related B indexes
//----------------------------------------------------------------
always @*
begin : loop_counter_process
loop_counter_new = loop_counter;
length_m1 = length - 1'b1;
loop_counter_dec = loop_counter - 1'b1;
B_word_index = loop_counter[12:5];
B_bit_index = B_bit_index_reg;
case (montprod_ctrl_reg)
CTRL_LOOP_INIT:
loop_counter_new = {length, 5'b00000}-1;
CTRL_LOOP_ITER:
begin
B_word_index = loop_counter[12:5];
B_bit_index = 5'h1f - loop_counter[4:0];
end
CTRL_L_STALLPIPE_D2:
loop_counter_new = loop_counter_dec;
default:
loop_counter_new = loop_counter;
endcase
end
//----------------------------------------------------------------
// prodcalc
//----------------------------------------------------------------
always @*
begin : prodcalc
case (montprod_ctrl_reg)
CTRL_LOOP_ITER:
//q = (s[length-1] ^ A[length-1]) & 1;
opa_addr_reg = length_m1;
default:
opa_addr_reg = word_index;
endcase
opb_addr_reg = B_word_index;
opm_addr_reg = word_index;
case (montprod_ctrl_reg)
CTRL_LOOP_ITER:
s_mem_addr = length_m1;
default:
s_mem_addr = word_index;
endcase
result_addr_reg = word_index_prev;
result_data_reg = s_mem_read_data;
case (montprod_ctrl_reg)
CTRL_EMIT_S:
tmp_result_we = 1'b1;
default:
tmp_result_we = 1'b0;
endcase
if (reset_word_index_LSW == 1'b1)
word_index_new = length_m1;
else if (reset_word_index_MSW == 1'b1)
word_index_new = 8'h0;
else if (montprod_ctrl_reg == CTRL_L_CALC_SDIV2)
word_index_new = word_index + 1'b1;
else
word_index_new = word_index - 1'b1;
end // prodcalc
always @*
begin : s_writer_process
shr_carry_new = 1'b0;
s_mux_new = SMUX_0;
s_mem_we_new = 1'b0;
case (montprod_ctrl_reg)
CTRL_INIT_S:
begin
s_mem_we_new = 1'b1;
s_mux_new = SMUX_0; // write 0
end
CTRL_L_CALC_SM:
begin
//s = (s + q*M + b*A) >>> 1;, if(q==1) S+= M. Takes (1..length) cycles.
s_mem_we_new = q_reg;
s_mux_new = SMUX_ADD_SM;
end
CTRL_L_CALC_SA:
begin
//s = (s + q*M + b*A) >>> 1;, if(b==1) S+= A. Takes (1..length) cycles.
s_mem_we_new = b_reg;
s_mux_new = SMUX_ADD_SA;
end
CTRL_L_CALC_SDIV2:
begin
//s = (s + q*M + b*A) >>> 1; s>>=1. Takes (1..length) cycles.
s_mux_new = SMUX_SHR;
s_mem_we_new = 1'b1;
end
default:
begin
end
endcase
add_carry_new_sa = 1'b0;
add_carry_new_sm = 1'b0;
case (s_mux_reg)
SMUX_ADD_SM:
add_carry_new_sm = add_carry_out_sm;
SMUX_ADD_SA:
add_carry_new_sa = add_carry_out_sa;
SMUX_SHR:
shr_carry_new = shr_carry_out;
default:
begin
end
endcase
end // prodcalc
//----------------------------------------------------------------
// montprod_ctrl
//
// Control FSM for the montgomery product calculator.
//----------------------------------------------------------------
always @*
begin : montprod_ctrl
ready_new = 1'b0;
ready_we = 1'b0;
montprod_ctrl_new = CTRL_IDLE;
montprod_ctrl_we = 1'b0;
reset_word_index_LSW = 1'b0;
reset_word_index_MSW = 1'b0;
case (montprod_ctrl_reg)
CTRL_IDLE:
begin
if (calculate)
begin
ready_new = 1'b0;
ready_we = 1'b1;
montprod_ctrl_new = CTRL_INIT_S;
montprod_ctrl_we = 1'b1;
reset_word_index_LSW = 1'b1;
end
else
begin
ready_new = 1'b1;
ready_we = 1'b1;
end
end
CTRL_INIT_S:
begin
if (word_index == 8'h0)
begin
montprod_ctrl_new = CTRL_LOOP_INIT;
montprod_ctrl_we = 1'b1;
end
end
CTRL_LOOP_INIT:
begin
montprod_ctrl_new = CTRL_LOOP_ITER;
montprod_ctrl_we = 1'b1;
end
//calculate q = (s - b * A) & 1;.
// Also abort loop if done.
CTRL_LOOP_ITER:
begin
reset_word_index_LSW = 1'b1;
montprod_ctrl_new = CTRL_LOOP_BQ;
montprod_ctrl_we = 1'b1;
end
CTRL_LOOP_BQ:
begin
reset_word_index_LSW = 1'b1;
montprod_ctrl_new = CTRL_L_CALC_SM;
montprod_ctrl_we = 1'b1;
end
CTRL_L_CALC_SM:
begin
if (word_index == 8'h0)
begin
reset_word_index_LSW = 1'b1;
montprod_ctrl_we = 1'b1;
montprod_ctrl_new = CTRL_L_STALLPIPE_SM;
end
end
CTRL_L_STALLPIPE_SM:
begin
montprod_ctrl_new = CTRL_L_CALC_SA;
montprod_ctrl_we = 1'b1;
reset_word_index_LSW = 1'b1;
end
CTRL_L_CALC_SA:
begin
if (word_index == 8'h0)
begin
reset_word_index_LSW = 1'b1;
montprod_ctrl_new = CTRL_L_STALLPIPE_SA;
montprod_ctrl_we = 1'b1;
end
end
CTRL_L_STALLPIPE_SA:
begin
montprod_ctrl_new = CTRL_L_CALC_SDIV2;
montprod_ctrl_we = 1'b1;
reset_word_index_MSW = 1'b1;
end
CTRL_L_CALC_SDIV2:
begin
if (word_index == length_m1)
begin
montprod_ctrl_new = CTRL_L_STALLPIPE_D2;
montprod_ctrl_we = 1'b1;
//reset_word_index = 1'b1;
end
end
CTRL_L_STALLPIPE_D2:
begin
montprod_ctrl_new = CTRL_LOOP_ITER; //loop
montprod_ctrl_we = 1'b1;
reset_word_index_LSW = 1'b1;
if (loop_counter == 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;
//reset_word_index_LSW = 1'b1;
end
CTRL_EMIT_S:
begin
if (DEBUG)
$display("EMIT_S word_index: %d", word_index);
if (word_index_prev == 8'h0)
begin
montprod_ctrl_new = CTRL_DONE;
montprod_ctrl_we = 1'b1;
end
end
CTRL_DONE:
begin
ready_new = 1'b1;
ready_we = 1'b1;
montprod_ctrl_new = CTRL_IDLE;
montprod_ctrl_we = 1'b1;
end
default:
begin
end
endcase // case (montprod_ctrl_reg)
end // montprod_ctrl
endmodule // montprod
//======================================================================
// EOF montprod.v
//======================================================================
