//======================================================================
//
// modexpa7_n_coeff.v
// -----------------------------------------------------------------------------
// Montgomery modulus-dependent coefficient calculation block.
//
// Authors: Pavel Shatov
//
// Copyright (c) 2017, 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 modexpa7_n_coeff #
	(
			//
			// This sets the address widths of memory buffers. Internal data
			// width is 32 bits, so for e.g. 1024-bit operands buffers must store
			// 1024 / 32 = 32 words, and these need 5-bit address bus, because
			// 2 ** 5 = 32.
			//
		parameter	OPERAND_ADDR_WIDTH = 5
	)
	(
		input											clk,
		input											rst_n,

		input											ena,
		output										rdy,

		output	[OPERAND_ADDR_WIDTH-1:0]	n_bram_addr,
		output	[OPERAND_ADDR_WIDTH-1:0]	n_coeff_bram_addr,

		input		[                32-1:0]	n_bram_out,

		output	[                32-1:0]	n_coeff_bram_in,
		output										n_coeff_bram_wr,

		input		[OPERAND_ADDR_WIDTH-1:0]	n_num_words
	);
	
		//
		// FSM Declaration
		//
	localparam	[ 7: 0]	FSM_STATE_IDLE		= 8'h00;
	
	localparam	[ 7: 0]	FSM_STATE_INIT_1	= 8'hA1;
	localparam	[ 7: 0]	FSM_STATE_INIT_2	= 8'hA2;
	localparam	[ 7: 0]	FSM_STATE_INIT_3	= 8'hA3;
	localparam	[ 7: 0]	FSM_STATE_INIT_4	= 8'hA4;
	localparam	[ 7: 0]	FSM_STATE_INIT_5	= 8'hA5;
	
	localparam	[ 7: 0]	FSM_STATE_CALC_1	= 8'hB1;
	localparam	[ 7: 0]	FSM_STATE_CALC_2	= 8'hB2;
	localparam	[ 7: 0]	FSM_STATE_CALC_3	= 8'hB3;
	localparam	[ 7: 0]	FSM_STATE_CALC_4	= 8'hB4;
	/*
	localparam	[ 7: 0]	FSM_STATE_CALC_5	= 8'hB5;
	localparam	[ 7: 0]	FSM_STATE_CALC_6	= 8'hB6;
	localparam	[ 7: 0]	FSM_STATE_CALC_7	= 8'hB7;
	localparam	[ 7: 0]	FSM_STATE_CALC_8	= 8'hB8;
	
	localparam	[ 7: 0]	FSM_STATE_SAVE_1	= 8'hC1;
	localparam	[ 7: 0]	FSM_STATE_SAVE_2	= 8'hC2;
	localparam	[ 7: 0]	FSM_STATE_SAVE_3	= 8'hC3;
	localparam	[ 7: 0]	FSM_STATE_SAVE_4	= 8'hC4;
	localparam	[ 7: 0]	FSM_STATE_SAVE_5	= 8'hC5;
	*/
	localparam	[ 7: 0]	FSM_STATE_STOP		= 8'hFF;
	
	reg	[ 7: 0]	fsm_state = FSM_STATE_IDLE;
	reg	[ 7: 0]	fsm_next_state;


		//
		// Enable Delay (Trigger)
		//
   reg ena_dly = 1'b0;
   wire ena_trig = ena && !ena_dly;
   always @(posedge clk) ena_dly <= ena;
	
		
		//
		// Parameters Latch
		//
	reg	[OPERAND_ADDR_WIDTH-1:0]	n_num_words_latch;

	always @(posedge clk)
		//
		if (fsm_next_state == FSM_STATE_INIT_1)
			n_num_words_latch <= n_num_words;

	
		//
		// Addresses
		//
	localparam	[OPERAND_ADDR_WIDTH-1:0]	bram_addr_zero = {OPERAND_ADDR_WIDTH{1'b0}};
	wire			[OPERAND_ADDR_WIDTH-1:0]	bram_addr_last = n_num_words_latch;
		
	
	/*
		//
		// Cycle Counters
		//
	reg	[OPERAND_ADDR_WIDTH+5:0]	cyc_cnt;		// cycle counter
		
	wire	[OPERAND_ADDR_WIDTH+5:0]	cyc_cnt_zero = {1'b0, {OPERAND_ADDR_WIDTH{1'b0}}, {5{1'b0}}};
	wire	[OPERAND_ADDR_WIDTH+5:0]	cyc_cnt_last = {n_num_words, 1'b1, {5{1'b1}}};
	wire	[OPERAND_ADDR_WIDTH+5:0]	cyc_cnt_next = cyc_cnt + 1'b1;

	wire	cyc_cnt_done = (cyc_cnt == cyc_cnt_last) ? 1'b1 : 1'b0;

	
	always @(posedge clk)
		//
		if (fsm_next_state == FSM_STATE_CALC_1)
			//
			case (fsm_state)
				FSM_STATE_INIT_2:	cyc_cnt <= cyc_cnt_zero;
				FSM_STATE_SAVE_5:	cyc_cnt <= cyc_cnt_done ? cyc_cnt : cyc_cnt_next;
			endcase
		*/	

	
	
		
		//
		// Ready Flag Logic
		//
	reg rdy_reg = 1'b1;
	assign rdy = rdy_reg;

   always @(posedge clk or negedge rst_n)
		//
		if (rst_n == 1'b0)						rdy_reg <= 1'b1;
		else begin
			if (fsm_state == FSM_STATE_IDLE)	rdy_reg <= ~ena_trig;
			if (fsm_state == FSM_STATE_STOP)	rdy_reg <= 1'b1;
		end
		
		
		//
		// Block Memories
		//
	reg	[OPERAND_ADDR_WIDTH-1:0]	n_addr;
	reg	[OPERAND_ADDR_WIDTH-1:0]	r_addr;
	reg	[OPERAND_ADDR_WIDTH-1:0]	b_addr;	
	reg	[OPERAND_ADDR_WIDTH-1:0]	nn_addr;
	reg	[OPERAND_ADDR_WIDTH-1:0]	t_addr_wr;
	reg	[OPERAND_ADDR_WIDTH-1:0]	t_addr_rd;
	
	reg	[31: 0]	r_data_in;
	reg	[31: 0]	b_data_in;
	reg	[31: 0]	nn_data_in;
	reg	[31: 0]	t_data_in;
	
	wire	[31: 0]	r_data_out;
	wire	[31: 0]	b_data_out;
	wire	[31: 0]	nn_data_out;
	wire	[31: 0]	t_data_out;
	
	reg				r_wren;
	reg				b_wren;
	reg				nn_wren;
	reg				t_wren;
		
	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH))
	bram_r (.clk(clk), .a_addr(r_addr), .a_wr(r_wren), .a_in(r_data_in), .a_out(r_data_out));

	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH))
	bram_b (.clk(clk), .a_addr(b_addr), .a_wr(b_wren), .a_in(b_data_in), .a_out(b_data_out));

	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH))
	bram_nn (.clk(clk), .a_addr(nn_addr), .a_wr(nn_wren), .a_in(nn_data_in), .a_out(nn_data_out));		

	bram_1rw_1ro_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH))
	bram_t (.clk(clk), .a_addr(t_addr_wr), .a_wr(t_wren), .a_in(t_data_in), .a_out(), .b_addr(t_addr_rd), .b_out(t_data_out));
		
	assign n_bram_addr = n_addr;
	
	wire	[OPERAND_ADDR_WIDTH-1:0]	n_addr_next  = n_addr + 1'b1;
	wire	[OPERAND_ADDR_WIDTH-1:0]	r_addr_next  = r_addr + 1'b1;
	wire	[OPERAND_ADDR_WIDTH-1:0]	b_addr_next  = b_addr + 1'b1;
	wire	[OPERAND_ADDR_WIDTH-1:0]	nn_addr_next = nn_addr + 1'b1;
	wire	[OPERAND_ADDR_WIDTH-1:0]	t_addr_wr_next  = t_addr_wr + 1'b1;
	wire	[OPERAND_ADDR_WIDTH-1:0]	t_addr_rd_next  = t_addr_rd + 1'b1;
	
	wire										n_addr_done  = (n_addr  == bram_addr_last) ? 1'b1 : 1'b0;
	wire										r_addr_done  = (r_addr  == bram_addr_last) ? 1'b1 : 1'b0;
	wire										b_addr_done  = (b_addr  == bram_addr_last) ? 1'b1 : 1'b0;
	wire										nn_addr_done = (nn_addr == bram_addr_last) ? 1'b1 : 1'b0;	
	wire										t_addr_wr_done  = (t_addr_wr  == bram_addr_last) ? 1'b1 : 1'b0;	
	wire										t_addr_rd_done  = (t_addr_rd  == bram_addr_last) ? 1'b1 : 1'b0;	
	
	
		//
		// Subtractor
		//
	wire	[31: 0]	add_s;
	wire				add_c_in;
	reg				add_b_lsb;
	reg				add_c_in_mask;
	reg				add_c_in_mask_dly;
	wire				add_c_out;
	
	assign add_c_in = add_c_out & ~add_c_in_mask;

	always @(posedge clk)
		//
		add_c_in_mask <= (fsm_next_state == FSM_STATE_INIT_2) ? 1'b1 : 1'b0;
		
	always @(posedge clk)
		//
		add_b_lsb <= (fsm_next_state == FSM_STATE_INIT_2) ? 1'b1 : 1'b0;
	
	always @(posedge clk)
		//
		add_c_in_mask_dly <= add_c_in_mask;
			
	ip_add32 add_inst
	(
		.clk		(clk),
		.a			(~n_bram_out),
		.b			({{31{1'b0}}, add_b_lsb}),
		.c_in		(add_c_in),
		.s			(add_s),
		.c_out	(add_c_out)
	);


		//
		// Multiplier
		//
	reg	[31: 0]	pe_a;
	reg	[31: 0]	pe_b;
	reg	[31: 0]	pe_t;
	reg	[31: 0]	pe_c_in;
	wire	[31: 0]	pe_p;
	wire	[31: 0]	pe_c_out;
	
	modexpa7_pe_mul pe2
	(
		.clk		(clk),
		.a			(pe_a),
		.b			(pe_b),
		.t			(pe_t),
		.c_in		(pe_c_in),
		.p			(pe_p),
		.c_out	(pe_c_out)
	);

		
	/*
	always @(posedge clk)
		//
		case (fsm_next_state)
			FSM_STATE_CALC_2:		f0_data_out_carry <= 1'b0;
			FSM_STATE_CALC_3,
			FSM_STATE_CALC_4,
			FSM_STATE_CALC_5,
			FSM_STATE_CALC_6:		f0_data_out_carry <= f0_data_out[31];
			default:					f0_data_out_carry <= 1'bX;
		endcase
	*/

	/*
	reg	sub_b_out_dly1;
	reg	f0_data_out_carry_dly1;
	reg	f0_data_out_carry_dly2;
	
	always @(posedge clk) sub_b_out_dly1 <= sub_b_out;
		
	always @(posedge clk) f0_data_out_carry_dly1 <= f0_data_out_carry;
	always @(posedge clk) f0_data_out_carry_dly2 <= f0_data_out_carry_dly1;
	
	reg	flag_keep_f;
	
	always @(posedge clk)
		//
		if (fsm_next_state == FSM_STATE_SAVE_1)
			flag_keep_f <= sub_b_out_dly1 & ~f0_data_out_carry_dly2;
	*/
	
	always @* t_addr_rd = r_addr + nn_addr;
	
	always @(posedge clk) begin
		//
		case (fsm_next_state)
		
			FSM_STATE_INIT_1:		n_addr <= bram_addr_zero;
			
			FSM_STATE_INIT_2,
			FSM_STATE_INIT_3,
			FSM_STATE_INIT_4,
			FSM_STATE_INIT_5:		n_addr <= !n_addr_done ? n_addr_next : n_addr;
			
		endcase
		//
		case (fsm_next_state)
			FSM_STATE_INIT_4:				nn_addr <= bram_addr_zero;
			FSM_STATE_INIT_5:				nn_addr <= nn_addr_next;
			FSM_STATE_CALC_1:
				case (fsm_state)
					FSM_STATE_INIT_5:		nn_addr <= bram_addr_zero;
				endcase
		endcase
		//
		case (fsm_next_state)
			FSM_STATE_INIT_4:		r_addr <= bram_addr_zero;
			FSM_STATE_INIT_5:		r_addr <= r_addr_next;
			FSM_STATE_CALC_1:		r_addr <= bram_addr_zero;
			FSM_STATE_CALC_2,
			FSM_STATE_CALC_3,
			FSM_STATE_CALC_4:		r_addr <= r_addr_next;
			
		endcase
		//
		case (fsm_next_state)
			
			FSM_STATE_INIT_4:		b_addr <= bram_addr_zero;
			
			FSM_STATE_INIT_5:		b_addr <= b_addr_next;
			
		endcase
		//
	end


	always @(posedge clk) begin
		//
		case (fsm_next_state)			
			FSM_STATE_INIT_4,
			FSM_STATE_INIT_5:		nn_wren	<= 1'b1;
			default:					nn_wren <= 1'b0;
		endcase
		//
		case (fsm_next_state)			
			FSM_STATE_INIT_4,
			FSM_STATE_INIT_5:		r_wren	<= 1'b1;
			default:					r_wren <= 1'b0;
		endcase
		//
		case (fsm_next_state)			
			FSM_STATE_INIT_4,
			FSM_STATE_INIT_5:		b_wren	<= 1'b1;
			default:					b_wren <= 1'b0;
		endcase
		/*
		case (fsm_next_state)			
			FSM_STATE_SAVE_3,
			FSM_STATE_SAVE_4,
			FSM_STATE_SAVE_5:		f_wren <= cyc_cnt_done;
			default:					f_wren <= 1'b0;
		endcase
		*/
	end
	
	always @(posedge clk) begin
		//
		case (fsm_next_state)
			FSM_STATE_INIT_4,
			FSM_STATE_INIT_5:		nn_data_in <= add_s;
			default:					nn_data_in <= {32{1'bX}};
		endcase
		//
		case (fsm_next_state)
			FSM_STATE_INIT_4,
			FSM_STATE_INIT_5:		r_data_in <= {{31{1'b0}}, add_c_in_mask_dly};
			default:					r_data_in <= {32{1'bX}};
		endcase
		//
		case (fsm_next_state)
			FSM_STATE_INIT_4,
			FSM_STATE_INIT_5:		b_data_in <= {{31{1'b0}}, add_c_in_mask_dly};
			default:					b_data_in <= {32{1'bX}};
		endcase
		/*
		case (fsm_next_state)
			FSM_STATE_CALC_3,
			FSM_STATE_CALC_4,
			FSM_STATE_CALC_5,
			FSM_STATE_CALC_6:		f1_data_in <= f0_data_out_shifted;
			default:					f1_data_in <= {32{1'bX}};
		endcase
		//
		case (fsm_next_state)
			FSM_STATE_CALC_5,
			FSM_STATE_CALC_6,
			FSM_STATE_CALC_7,
			FSM_STATE_CALC_8:		f2_data_in <= sub_d;
			default:					f2_data_in <= {32{1'bX}};
		endcase
		//
		case (fsm_next_state)
			FSM_STATE_SAVE_3,
			FSM_STATE_SAVE_4,
			FSM_STATE_SAVE_5:		f_data_in <= flag_keep_f ? f1_data_out : f2_data_out;
			default:					f_data_in <= {32{1'bX}};
		endcase
		*/
	end


	
		//
		// FSM Transition Logic
		//
	always @(posedge clk or negedge rst_n)
		//
		if (rst_n == 1'b0)	fsm_state <= FSM_STATE_IDLE;
		else						fsm_state <= fsm_next_state;
	
	
	always @* begin
		//
		fsm_next_state = FSM_STATE_STOP;
		//
		case (fsm_state)

			FSM_STATE_IDLE:		if (ena_trig)				fsm_next_state = FSM_STATE_INIT_1;
										else							fsm_next_state = FSM_STATE_IDLE;
												
			FSM_STATE_INIT_1:										fsm_next_state = FSM_STATE_INIT_2;

			FSM_STATE_INIT_2:										fsm_next_state = FSM_STATE_INIT_3;

			FSM_STATE_INIT_3:										fsm_next_state = FSM_STATE_INIT_4;

			FSM_STATE_INIT_4:										fsm_next_state = FSM_STATE_INIT_5;
			
			FSM_STATE_INIT_5:		if (nn_addr_done)			fsm_next_state = FSM_STATE_CALC_1;
										else							fsm_next_state = FSM_STATE_INIT_5;

			FSM_STATE_CALC_1:										fsm_next_state = FSM_STATE_CALC_2;

			FSM_STATE_CALC_2:										fsm_next_state = FSM_STATE_CALC_3;

			FSM_STATE_CALC_3:										fsm_next_state = FSM_STATE_CALC_4;
			
			FSM_STATE_CALC_4:										fsm_next_state = FSM_STATE_STOP;//FSM_STATE_CALC_5;
			/*
			FSM_STATE_CALC_5:										fsm_next_state = FSM_STATE_CALC_6;
										
			FSM_STATE_CALC_6:		if (f1_addr_done)			fsm_next_state = FSM_STATE_CALC_7;
										else							fsm_next_state = FSM_STATE_CALC_6;
										
			FSM_STATE_CALC_7:										fsm_next_state = FSM_STATE_CALC_8;
			
			FSM_STATE_CALC_8:										fsm_next_state = FSM_STATE_SAVE_1;
			
			FSM_STATE_SAVE_1:										fsm_next_state = FSM_STATE_SAVE_2;
			
			FSM_STATE_SAVE_2:										fsm_next_state = FSM_STATE_SAVE_3;
			
			FSM_STATE_SAVE_3:										fsm_next_state = FSM_STATE_SAVE_4;
			
			FSM_STATE_SAVE_4:		if (f12_addr_done_dly)	fsm_next_state = FSM_STATE_SAVE_5;
										else							fsm_next_state = FSM_STATE_SAVE_4;

			FSM_STATE_SAVE_5:		if (cyc_cnt_done)			fsm_next_state = FSM_STATE_STOP;
										else							fsm_next_state = FSM_STATE_CALC_1;
			*/						
			FSM_STATE_STOP:										fsm_next_state = FSM_STATE_IDLE;

		endcase
	end


endmodule

//======================================================================
// End of file
//======================================================================