//------------------------------------------------------------------------------
//
// modular_multiplier_256.v
// -----------------------------------------------------------------------------
// Modular multiplier.
//
// Authors: Pavel Shatov
//
// Copyright (c) 2015-2016, NORDUnet A/S
//
// 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 modular_multiplier_256
(
clk, rst_n,
ena, rdy,
a_addr, b_addr, n_addr, p_addr, p_wren,
a_din, b_din, n_din, p_dout
);
//
// Constants
//
localparam OPERAND_NUM_WORDS = 8;
localparam WORD_COUNTER_WIDTH = 3;
//
// Handy Numbers
//
localparam [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_ZERO = 0;
localparam [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_LAST = OPERAND_NUM_WORDS - 1;
//
// Handy Functions
//
function [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_NEXT_OR_ZERO;
input [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_CURRENT;
begin
WORD_INDEX_NEXT_OR_ZERO = (WORD_INDEX_CURRENT < WORD_INDEX_LAST) ?
WORD_INDEX_CURRENT + 1'b1 : WORD_INDEX_ZERO;
end
endfunction
function [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_PREVIOUS_OR_LAST;
input [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_CURRENT;
begin
WORD_INDEX_PREVIOUS_OR_LAST = (WORD_INDEX_CURRENT > WORD_INDEX_ZERO) ?
WORD_INDEX_CURRENT - 1'b1 : WORD_INDEX_LAST;
end
endfunction
//
// Ports
//
input wire clk; // system clock
input wire rst_n; // active-low async reset
input wire ena; // enable input
output wire rdy; // ready output
output wire [WORD_COUNTER_WIDTH-1:0] a_addr; // index of current A word
output wire [WORD_COUNTER_WIDTH-1:0] b_addr; // index of current B word
output wire [WORD_COUNTER_WIDTH-1:0] n_addr; // index of current N word
output wire [WORD_COUNTER_WIDTH-1:0] p_addr; // index of current P word
output wire p_wren; // store current P word now
input wire [ 31:0] a_din; // A
input wire [ 31:0] b_din; // B
input wire [ 31:0] n_din; // N (must be P-256!)
output wire [ 31:0] p_dout; // P = A * B mod N
//
// Word Indices
//
reg [WORD_COUNTER_WIDTH-1:0] index_a;
reg [WORD_COUNTER_WIDTH-1:0] index_b;
/* map registers to output ports */
assign a_addr = index_a;
assign b_addr = index_b;
//
// FSM
//
localparam FSM_SHREG_WIDTH = (1 * OPERAND_NUM_WORDS + 1) + (2 * OPERAND_NUM_WORDS + 1) + (2 * OPERAND_NUM_WORDS + 2) + (0 * OPERAND_NUM_WORDS + 2) + 1;
reg [FSM_SHREG_WIDTH-1:0] fsm_shreg;
assign rdy = fsm_shreg[0];
wire [1 * OPERAND_NUM_WORDS-1:0] fsm_shreg_inc_index_a = fsm_shreg[FSM_SHREG_WIDTH - (0 * OPERAND_NUM_WORDS + 1) : FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 0)];
wire [1 * OPERAND_NUM_WORDS-1:0] fsm_shreg_store_word_a = fsm_shreg[FSM_SHREG_WIDTH - (0 * OPERAND_NUM_WORDS + 2) : FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 1)];
wire [2 * OPERAND_NUM_WORDS-1:0] fsm_shreg_inc_index_b = fsm_shreg[FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 1) : FSM_SHREG_WIDTH - (3 * OPERAND_NUM_WORDS + 1)];
wire [2 * OPERAND_NUM_WORDS-2:0] fsm_shreg_store_si_msb = fsm_shreg[FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 2) : FSM_SHREG_WIDTH - (3 * OPERAND_NUM_WORDS + 1)];
wire [0 * OPERAND_NUM_WORDS-0:0] fsm_shreg_store_si_lsb = fsm_shreg[FSM_SHREG_WIDTH - (3 * OPERAND_NUM_WORDS + 2) : FSM_SHREG_WIDTH - (3 * OPERAND_NUM_WORDS + 2)];
wire [2 * OPERAND_NUM_WORDS-2:0] fsm_shreg_shift_si = fsm_shreg[FSM_SHREG_WIDTH - (3 * OPERAND_NUM_WORDS + 3) : FSM_SHREG_WIDTH - (5 * OPERAND_NUM_WORDS + 1)];
wire [0 * OPERAND_NUM_WORDS-0:0] fsm_shreg_mask_cw1_sum = fsm_shreg[FSM_SHREG_WIDTH - (3 * OPERAND_NUM_WORDS + 4) : FSM_SHREG_WIDTH - (3 * OPERAND_NUM_WORDS + 4)];
wire [2 * OPERAND_NUM_WORDS-1:0] fsm_shreg_store_c_word = fsm_shreg[FSM_SHREG_WIDTH - (3 * OPERAND_NUM_WORDS + 5) : FSM_SHREG_WIDTH - (5 * OPERAND_NUM_WORDS + 4)];
wire [0 * OPERAND_NUM_WORDS-0:0] fsm_shreg_reduce_start = fsm_shreg[FSM_SHREG_WIDTH - (5 * OPERAND_NUM_WORDS + 5) : FSM_SHREG_WIDTH - (5 * OPERAND_NUM_WORDS + 5)];
wire [0 * OPERAND_NUM_WORDS-0:0] fsm_shreg_reduce_stop = fsm_shreg[FSM_SHREG_WIDTH - (5 * OPERAND_NUM_WORDS + 6) : FSM_SHREG_WIDTH - (5 * OPERAND_NUM_WORDS + 6)];
wire inc_index_a = |fsm_shreg_inc_index_a;
wire store_word_a = |fsm_shreg_store_word_a;
wire inc_index_b = |fsm_shreg_inc_index_b;
wire clear_mac_ab = |fsm_shreg_inc_index_b;
wire shift_wide_a = |fsm_shreg_inc_index_b;
wire enable_mac_ab = |fsm_shreg_inc_index_b;
wire store_si_msb = |fsm_shreg_store_si_msb;
wire store_si_lsb = fsm_shreg_store_si_lsb;
wire shift_si = |fsm_shreg_shift_si;
wire mask_cw1_sum = fsm_shreg_mask_cw1_sum;
wire store_c_word = |fsm_shreg_store_c_word;
wire reduce_start = fsm_shreg_reduce_start;
wire reduce_stop = fsm_shreg_reduce_stop;
//
// FSM Logic
//
wire reduce_done;
always @(posedge clk or negedge rst_n)
//
if (rst_n == 1'b0)
//
fsm_shreg <= {{FSM_SHREG_WIDTH-1{1'b0}}, 1'b1};
//
else begin
//
if (rdy)
fsm_shreg <= {ena, {FSM_SHREG_WIDTH-2{1'b0}}, ~ena};
//
else if (!reduce_stop || reduce_done)
fsm_shreg <= {1'b0, fsm_shreg[FSM_SHREG_WIDTH-1:1]};
//
end
//
// Word Index Increment Logic
//
reg index_b_ff;
always @(posedge clk)
//
if (inc_index_b) index_b_ff <= ~index_b_ff;
else index_b_ff <= 1'b0;
always @(posedge clk)
//
if (rdy) begin
//
index_a <= WORD_INDEX_ZERO;
index_b <= WORD_INDEX_LAST;
//
end else begin
//
if (inc_index_a) index_a <= WORD_INDEX_NEXT_OR_ZERO(index_a);
if (inc_index_b && !index_b_ff) index_b <= WORD_INDEX_PREVIOUS_OR_LAST(index_b);
//
end
//
// Wide Operand Buffer
//
reg [255:0] buf_a_wide;
always @(posedge clk)
//
if (store_word_a)
buf_a_wide <= {buf_a_wide[16 +: 256 - 3 * 16], {a_din[15:0], a_din[31:16]}, buf_a_wide[256 - 2 * 16 +: 16]};
else if (shift_wide_a)
buf_a_wide <= {buf_a_wide[256-(16+1):0], buf_a_wide[256-16+:16]};
//
// Multiplier Array
//
wire mac_inhibit; // control signal to pause all accumulators
wire [46: 0] mac[0:15]; // outputs of all accumulators
reg [15: 0] mac_clear; // individual per-accumulator clear flag
assign mac_inhibit = ~enable_mac_ab;
always @(posedge clk)
//
if (!clear_mac_ab)
mac_clear <= {16{1'b1}};
else begin
if (mac_clear == {16{1'b1}})
mac_clear <= {{14{1'b0}}, 1'b1, {1{1'b0}}};
else
mac_clear <= (mac_clear[15] == 1'b0) ? {mac_clear[14:0], 1'b0} : {16{1'b1}};
end
//
// Array of parallel multipliers
//
genvar i;
generate for (i=0; i<16; i=i+1)
begin : gen_mac_array
//
mac16_wrapper mac16_inst
(
.clk (clk),
.ce (~mac_inhibit),
.clr (mac_clear[i]),
.a (buf_a_wide[16*i+:16]),
.b (index_b_ff ? b_din[15:0] : b_din[31:16]),
.s (mac[i])
);
//
end
endgenerate
//
// Intermediate Words
//
reg [47*(2*OPERAND_NUM_WORDS-1)-1:0] si_msb;
reg [47*(2*OPERAND_NUM_WORDS-0)-1:0] si_lsb;
wire [47*(2*OPERAND_NUM_WORDS-1)-1:0] si_msb_new;
wire [47*(2*OPERAND_NUM_WORDS-0)-1:0] si_lsb_new;
generate for (i=0; i<16; i=i+1)
begin : gen_si_lsb_new
assign si_lsb_new[47*i+:47] = mac[15-i];
end
endgenerate
generate for (i=1; i<16; i=i+1)
begin : gen_si_msb_new
assign si_msb_new[47*(15-i)+:47] = mac_clear[i] ? mac[i] : si_msb[47*(15-i)+:47];
end
endgenerate
always @(posedge clk) begin
//
if (shift_si) begin
si_msb <= {{2*47{1'b0}}, si_msb[15*47-1:2*47]};
si_lsb <= {si_msb[2*47-1:0], si_lsb[16*47-1:2*47]};
end else begin
if (store_si_msb)
si_msb <= si_msb_new;
if (store_si_lsb)
si_lsb <= si_lsb_new;
end
end
//
// Accumulators
//
wire [46: 0] add47_cw0_s;
wire [46: 0] add47_cw1_s;
//
// cw0, b, cw1, b
//
reg [30: 0] si_prev_dly;
reg [15: 0] si_next_dly;
always @(posedge clk)
//
if (shift_si)
si_prev_dly <= si_lsb[93:63];
else
si_prev_dly <= {31{1'b0}};
always @(posedge clk)
//
si_next_dly <= si_lsb[62:47];
wire [46: 0] add47_cw0_a = si_lsb[46:0];
wire [46: 0] add47_cw0_b = {{16{1'b0}}, si_prev_dly};
wire [46: 0] add47_cw1_a = add47_cw0_s;
wire [46: 0] add47_cw1_b = {{15{1'b0}}, si_next_dly, mask_cw1_sum ? {16{1'b0}} : {1'b0, add47_cw1_s[46:32]}};
adder47_wrapper add47_cw0_inst
(
.clk (clk),
.a (add47_cw0_a),
.b (add47_cw0_b),
.s (add47_cw0_s)
);
adder47_wrapper add47_cw1_inst
(
.clk (clk),
.a (add47_cw1_a),
.b (add47_cw1_b),
.s (add47_cw1_s)
);
//
// Full-Size Product
//
reg [WORD_COUNTER_WIDTH:0] bram_c_addr;
wire [WORD_COUNTER_WIDTH:0] reduce_c_addr;
wire [ 31:0] reduce_c_word;
always @(posedge clk)
//
if (store_c_word)
bram_c_addr <= bram_c_addr + 1'b1;
else
bram_c_addr <= {2*WORD_COUNTER_WIDTH{1'b0}};
bram_1rw_1ro_readfirst #
(
.MEM_WIDTH (32),
.MEM_ADDR_BITS (WORD_COUNTER_WIDTH + 1)
)
bram_c_inst
(
.clk (clk),
.a_addr (bram_c_addr),
.a_wr (store_c_word),
.a_in (add47_cw1_s[31:0]),
.a_out (),
.b_addr (reduce_c_addr),
.b_out (reduce_c_word)
);
//
// Reduction Stage
//
modular_reductor_256 reduce_256_inst
(
.clk (clk),
.rst_n (rst_n),
.ena (reduce_start),
.rdy (reduce_done),
.x_addr (reduce_c_addr),
.n_addr (n_addr),
.p_addr (p_addr),
.p_wren (p_wren),
.x_din (reduce_c_word),
.n_din (n_din),
.p_dout (p_dout)
);
endmodule
//------------------------------------------------------------------------------
// End-of-File
//------------------------------------------------------------------------------
