Wide operand loader needs simplification...

3 files changed, 1617 insertions, 1193 deletions

diff --git a/src/rtl/modexpa7_systolic_multiplier.v b/src/rtl/modexpa7_systolic_multiplier.v
index f53354e..a1e141e 100644
--- a/src/rtl/modexpa7_systolic_multiplier.v
+++ b/src/rtl/modexpa7_systolic_multiplier.v
@@ -1,1229 +1,393 @@
-//======================================================================

-//

-// modexpa7_systolic_multiplier.v

-// -----------------------------------------------------------------------------

-// Systolic Montgomery multiplier.

-//

-// 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_systolic_multiplier #

-	(

-			//

-			// This sets the address widths of memory buffers. Internal data

-			// width is 32 bits, so for e.g. 2048-bit operands buffers must store

-			// 2048 / 32 = 64 words, and these need 6-bit address bus, because

-			// 2 ** 6 = 64.

-			//

-		parameter	OPERAND_ADDR_WIDTH		= 4,

-		

-			//

-			// Explain.

-			//

-		parameter	SYSTOLIC_ARRAY_POWER		= 1

-	)

-	(

-		input											clk,

-		input											rst_n,

-

-		input											ena,

-		output										rdy,

-

+//======================================================================
+//
+// modexpa7_systolic_multiplier.v
+// -----------------------------------------------------------------------------
+// Systolic Montgomery multiplier.
+//
+// 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_systolic_multiplier #
+	(
+			//
+			// This sets the address widths of memory buffers. Internal data
+			// width is 32 bits, so for e.g. 2048-bit operands buffers must store
+			// 2048 / 32 = 64 words, and these need 6-bit address bus, because
+			// 2 ** 6 = 64.
+			//
+		parameter	OPERAND_ADDR_WIDTH		= 4,
+		
+			//
+			// Explain.
+			//
+		parameter	SYSTOLIC_ARRAY_POWER		= 2
+	)
+	(
+		input											clk,
+		input											rst_n,
+
+		input											ena,
+		output										rdy,
+
 		output	[OPERAND_ADDR_WIDTH-1:0]	a_bram_addr,
 		output	[OPERAND_ADDR_WIDTH-1:0]	b_bram_addr,
 		output	[OPERAND_ADDR_WIDTH-1:0]	n_bram_addr,
 		output	[OPERAND_ADDR_WIDTH-1:0]	n_coeff_bram_addr,
 		output	[OPERAND_ADDR_WIDTH-1:0]	r_bram_addr,
-

+
 		input		[                32-1:0]	a_bram_out,
 		input		[                32-1:0]	b_bram_out,
 		input		[                32-1:0]	n_bram_out,
 		input		[                32-1:0]	n_coeff_bram_out,
-

-		output	[                32-1:0]	r_bram_in,

-		output										r_bram_wr,

-

-		input		[OPERAND_ADDR_WIDTH-1:0]	ab_num_words

-	);

-	

-		

-		//

-		// Include Settings

-		//

-	`include "pe/modexpa7_primitive_switch.v"

-	`include "modexpa7_settings.v"

-		

-

-		//

-		// FSM Declaration

-		//

-	localparam	[ 7: 0]	FSM_STATE_IDLE								= 8'h00;

-

-	localparam	[ 7: 0]	FSM_STATE_LOAD_B_START					= 8'h11;

-	localparam	[ 7: 0]	FSM_STATE_LOAD_B_SHIFT					= 8'h12;

-	localparam	[ 7: 0]	FSM_STATE_LOAD_B_WRITE					= 8'h13;

-	localparam	[ 7: 0]	FSM_STATE_LOAD_B_FINAL					= 8'h14;

-

-	localparam	[ 7: 0]	FSM_STATE_LOAD_N_COEFF_START			= 8'h21;

-	localparam	[ 7: 0]	FSM_STATE_LOAD_N_COEFF_SHIFT			= 8'h22;

-	localparam	[ 7: 0]	FSM_STATE_LOAD_N_COEFF_WRITE			= 8'h23;

-	localparam	[ 7: 0]	FSM_STATE_LOAD_N_COEFF_FINAL			= 8'h24;

-

-	localparam	[ 7: 0]	FSM_STATE_LOAD_N_START					= 8'h31;

-	localparam	[ 7: 0]	FSM_STATE_LOAD_N_SHIFT					= 8'h32;

-	localparam	[ 7: 0]	FSM_STATE_LOAD_N_WRITE					= 8'h33;

-	localparam	[ 7: 0]	FSM_STATE_LOAD_N_FINAL					= 8'h34;

-

-	localparam	[ 7: 0]	FSM_STATE_MULT_A_B_START				= 8'h41;

-	localparam	[ 7: 0]	FSM_STATE_MULT_A_B_CRUNCH				= 8'h42;

-	localparam	[ 7: 0]	FSM_STATE_MULT_A_B_RELOAD				= 8'h43;

-	localparam	[ 7: 0]	FSM_STATE_MULT_A_B_FINAL				= 8'h44;

-

-	localparam	[ 7: 0]	FSM_STATE_MULT_AB_N_COEFF_START		= 8'h51;

-	localparam	[ 7: 0]	FSM_STATE_MULT_AB_N_COEFF_CRUNCH		= 8'h52;

-	localparam	[ 7: 0]	FSM_STATE_MULT_AB_N_COEFF_RELOAD		= 8'h53;

-	localparam	[ 7: 0]	FSM_STATE_MULT_AB_N_COEFF_FINAL		= 8'h54;

-

-	localparam	[ 7: 0]	FSM_STATE_MULT_Q_N_START				= 8'h61;

-	localparam	[ 7: 0]	FSM_STATE_MULT_Q_N_CRUNCH				= 8'h62;

-	localparam	[ 7: 0]	FSM_STATE_MULT_Q_N_RELOAD				= 8'h63;

-	localparam	[ 7: 0]	FSM_STATE_MULT_Q_N_FINAL				= 8'h64;

-	

-	localparam	[ 7: 0]	FSM_STATE_SAVE_START						= 8'h71;

-	localparam	[ 7: 0]	FSM_STATE_SAVE_WRITE						= 8'h72;

-	localparam	[ 7: 0]	FSM_STATE_SAVE_FINAL						= 8'h73;	

-	

-	localparam	[ 7: 0]	FSM_STATE_STOP								= 8'hFF;

-	

-		//

-		// FSM State / Next State

-		//

-	reg	[ 7: 0]	fsm_state = FSM_STATE_IDLE;

-	reg	[ 7: 0]	fsm_next_state;

-

-

-		//

-		// Enable Delay and Trigger

-		//

-   reg ena_dly = 1'b0;

-	

-		/* delay enable by one clock cycle */

-   always @(posedge clk) ena_dly <= ena;

-

-		/* trigger new operation when enable goes high */

-   wire ena_trig = ena && !ena_dly;

-	

-	

-		//

-		// Ready Flag Logic

-		//

-	reg rdy_reg = 1'b1;

-	assign rdy = rdy_reg;

-

-   always @(posedge clk or negedge rst_n)

-		

-			/* reset flag */

-		if (rst_n == 1'b0) rdy_reg <= 1'b1;

-		else begin

-		

-				/* clear flag when operation is started */

-			if (fsm_state == FSM_STATE_IDLE)	rdy_reg <= ~ena_trig;

-			

-				/* set flag after operation is finished */

-			if (fsm_state == FSM_STATE_STOP)	rdy_reg <= 1'b1;			

-			

-		end

-		

-		

-		//

-		// Parameters Latch

-		//

-	reg	[OPERAND_ADDR_WIDTH-1:0]	ab_num_words_latch;

-

-		/* save number of words in a and b when new operation starts */

-	always @(posedge clk)

-		//

-		if (fsm_next_state == FSM_STATE_LOAD_B_START)

-			ab_num_words_latch <= ab_num_words;

-			

-			

-		//

-		// Systolic Cycle Counters

-		//

-		

-		/* handy values */

-	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_zero = {SYSTOLIC_CNTR_WIDTH{1'b0}};

-	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_last = ab_num_words_latch[OPERAND_ADDR_WIDTH-1:SYSTOLIC_ARRAY_POWER];

-	

-		/* counters */

-	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_init;

-	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_load;

-	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_unload;

-		

-		/* handy increment values */

-	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_init_next		= syst_cnt_init   + 1'b1;

-	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_load_next		= syst_cnt_load   + 1'b1;

-	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_unload_next		= syst_cnt_unload + 1'b1;

-

-		/* handy stop flags */

-	wire										syst_cnt_init_done		= (syst_cnt_init   == syst_cnt_last) ? 1'b1 : 1'b0;

-	wire										syst_cnt_load_done		= (syst_cnt_load   == syst_cnt_last) ? 1'b1 : 1'b0;

-	wire										syst_cnt_unload_done		= (syst_cnt_unload == syst_cnt_last) ? 1'b1 : 1'b0;

-

-		/* delayed load counter */

-	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_load_dly;

-	always @(posedge clk) syst_cnt_load_dly <= syst_cnt_load;

-

-

-		//

-		// Multiplier Iteration Counter

-		//

-		

-		/* handy values */

-	wire	[SYSTOLIC_ARRAY_POWER-1:0]	mult_cnt_zero = {SYSTOLIC_ARRAY_POWER{1'b0}};

-	wire	[SYSTOLIC_ARRAY_POWER-1:0]	mult_cnt_last = {SYSTOLIC_ARRAY_POWER{1'b1}};

-	

-		/* counter */

-	reg	[SYSTOLIC_ARRAY_POWER-1:0]	mult_cnt;

-	

-		/* handy increment value and stop flag */

-	wire	[SYSTOLIC_ARRAY_POWER-1:0]	mult_cnt_next = mult_cnt + 1'b1;

-	wire										mult_cnt_done = (mult_cnt == mult_cnt_last) ? 1'b1 : 1'b0;

-			

-			

-		//

-		// Initialization Counter Control Logic

-		//

-	always @(posedge clk) begin

-		//

-		case (fsm_state)

-			FSM_STATE_LOAD_B_START,

-			FSM_STATE_LOAD_N_COEFF_START,

-			FSM_STATE_LOAD_N_START:				mult_cnt <= mult_cnt_zero;

+
+		output	[                32-1:0]	r_bram_in,
+		output										r_bram_wr,
+
+		input		[OPERAND_ADDR_WIDTH-1:0]	n_num_words
+	);
+	
+		
+		/*
+		 * Include Settings
+		 */
+	`include "pe/modexpa7_primitive_switch.v"
+	`include "modexpa7_settings.v"
+		
+
+		/*
+		 * FSM Declaration
+		 */
+	localparam	[ 7: 0]	FSM_STATE_IDLE				= 8'h00;
+	
+	localparam	[ 7: 0]	FSM_STATE_LOAD_START		= 8'h11;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_SHIFT		= 8'h12;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_WRITE		= 8'h13;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_FINAL		= 8'h14;
+

+	localparam	[ 7: 0]	FSM_STATE_MULT_START		= 8'h21;
+	localparam	[ 7: 0]	FSM_STATE_MULT_CRUNCH	= 8'h22;
+	localparam	[ 7: 0]	FSM_STATE_MULT_FINAL		= 8'h23;
+	
+	localparam	[ 7: 0]	FSM_STATE_STOP				= 8'hFF;

+	
+		/*
+		 * FSM State / Next State
+		 */
+	reg	[ 7: 0]	fsm_state = FSM_STATE_IDLE;
+	reg	[ 7: 0]	fsm_next_state;
+
+
+		/*
+		 * Enable Delay and Trigger
+		 */
+   reg ena_dly = 1'b0;
+	
+		// delay enable by one clock cycle
+   always @(posedge clk) ena_dly <= ena;
+
+		// trigger new operation when enable goes high
+   wire ena_trig = ena && !ena_dly;
+	
+	
+		/*
+		 * Ready Flag Logic
+		 */
+	reg rdy_reg = 1'b1;
+	assign rdy = rdy_reg;
+
+   always @(posedge clk or negedge rst_n)
+		
+			// reset flag
+		if (rst_n == 1'b0) rdy_reg <= 1'b1;
+		else begin
+		
+				// clear flag when operation is started
+			if (fsm_state == FSM_STATE_IDLE)	rdy_reg <= ~ena_trig;
+			
+				// set flag after operation is finished
+			if (fsm_state == FSM_STATE_STOP)	rdy_reg <= 1'b1;			
+			
+		end
+		
+		
+		/*
+		 * Parameters Latch
+		 */
+	reg	[OPERAND_ADDR_WIDTH-1:0]	n_num_words_latch;
+
+		// save number of words in n when new operation starts
+	always @(posedge clk)
+		//
+		if ((fsm_state == FSM_STATE_IDLE) && ena_trig)
+			n_num_words_latch <= n_num_words;
 			

-			FSM_STATE_LOAD_B_SHIFT,

-			FSM_STATE_LOAD_N_COEFF_SHIFT,

-			FSM_STATE_LOAD_N_SHIFT:				mult_cnt <= mult_cnt_next;

-		endcase

-		//

-		case (fsm_state)

-			FSM_STATE_LOAD_B_START,

-			FSM_STATE_LOAD_N_COEFF_START,

-			FSM_STATE_LOAD_N_START:				syst_cnt_init <= syst_cnt_zero;

-			

-			FSM_STATE_LOAD_B_WRITE,

-			FSM_STATE_LOAD_N_COEFF_WRITE,

-			FSM_STATE_LOAD_N_WRITE:				syst_cnt_init <= !syst_cnt_init_done ? syst_cnt_init_next : syst_cnt_init;

-		endcase

-		//

-	end

-	

-	

-		//

-		// Operand Loader

-		//

-	

-		/*

-		 * Explain how parallelized loader works here...

-		 *

-		 */

-	

-		/* loader banks */

-	localparam	[ 1: 0]	LOADER_ADDR_MSB_B				= 2'd0;

-	localparam	[ 1: 0]	LOADER_ADDR_MSB_N_COEFF		= 2'd1;

-	localparam	[ 1: 0]	LOADER_ADDR_MSB_N				= 2'd2;

-	

-		/* loader input */

-	reg	[                  2-1:0]	loader_addr_msb[0:SYSTOLIC_ARRAY_LENGTH-1];	

-	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	loader_addr_lsb[0:SYSTOLIC_ARRAY_LENGTH-1];

-	reg										loader_wren    [0:SYSTOLIC_ARRAY_LENGTH-1];

-	reg	[                 32-1:0]	loader_din     [0:SYSTOLIC_ARRAY_LENGTH-1];

-	

-		/* loader output */

-	wire	[                 32-1:0]	loader_dout    [0:SYSTOLIC_ARRAY_LENGTH-1];

 			

-		/* generate parallelized loader */

-		

-		//

-		// Loader currently stores B, N_COEFF and N, it can be coded another way

-		// to initially store B, then AB, then Q. Some memory can be saved thay way.

-		// Maybe later...

-		//

-		

-	genvar i;

-	generate for (i=0; i<SYSTOLIC_ARRAY_LENGTH; i=i+1)

-		//

-		begin : gen_bram_1rw_readfirst_loader

-			//

-			bram_1rw_readfirst #

-			(

-				.MEM_WIDTH		(32),

-				.MEM_ADDR_BITS	(SYSTOLIC_CNTR_WIDTH + 2)

-			)

-			bram_loader

-			(

-				.clk		(clk),

-				.a_addr	({loader_addr_msb[i], loader_addr_lsb[i]}),

-				.a_wr		(loader_wren[i]),

-				.a_in		(loader_din[i]),

-				.a_out	(loader_dout[i])

-			);

-			//

-		end

-		//

-	endgenerate

-	

-

-		//

-		// Block Memory Addresses

-		//

-		

 		/*

-		 * Explain why there are two memory sizes.

-		 *

+		 * Counters

 		 */

-		

-		/* the very first addresses */

-	wire	[OPERAND_ADDR_WIDTH-1:0]	bram_addr_zero			= {      {OPERAND_ADDR_WIDTH{1'b0}}};

-	wire	[OPERAND_ADDR_WIDTH  :0]	bram_addr_ext_zero	= {1'b0, {OPERAND_ADDR_WIDTH{1'b0}}};

-	

-		/* the very last addresses */

-	wire	[OPERAND_ADDR_WIDTH-1:0]	bram_addr_last     = {ab_num_words_latch};

-	wire	[OPERAND_ADDR_WIDTH  :0]	bram_addr_ext_last = {ab_num_words_latch, 1'b1};

-

-		/* address registers */

-	reg	[OPERAND_ADDR_WIDTH-1:0]	a_addr;

-	reg	[OPERAND_ADDR_WIDTH-1:0]	b_addr;

-	reg	[OPERAND_ADDR_WIDTH-1:0]	n_coeff_addr;

-	reg	[OPERAND_ADDR_WIDTH-1:0]	n_addr;

-	reg	[OPERAND_ADDR_WIDTH  :0]	ab_addr_ext;

-	reg	[OPERAND_ADDR_WIDTH-1:0]	q_addr;

-	reg	[OPERAND_ADDR_WIDTH  :0]	qn_addr_ext;

-	reg	[OPERAND_ADDR_WIDTH-1:0]	s_addr;

-	reg	[OPERAND_ADDR_WIDTH-1:0]	sn_addr;

-	reg	[OPERAND_ADDR_WIDTH-1:0]	r_addr;

-		

-		/* handy increment values */

-	wire	[OPERAND_ADDR_WIDTH-1:0]	a_addr_next			= a_addr       + 1'b1;

-	wire	[OPERAND_ADDR_WIDTH-1:0]	b_addr_next			= b_addr       + 1'b1;

-	wire	[OPERAND_ADDR_WIDTH-1:0]	n_coeff_addr_next	= n_coeff_addr + 1'b1;

-	wire	[OPERAND_ADDR_WIDTH-1:0]	n_addr_next			= n_addr       + 1'b1;

-	wire	[OPERAND_ADDR_WIDTH  :0]	ab_addr_ext_next	= ab_addr_ext  + 1'b1;

-	wire	[OPERAND_ADDR_WIDTH-1:0]	q_addr_next			= q_addr       + 1'b1;

-	wire	[OPERAND_ADDR_WIDTH  :0]	qn_addr_ext_next	= qn_addr_ext  + 1'b1;

-	wire	[OPERAND_ADDR_WIDTH-1:0]	s_addr_next	= s_addr  + 1'b1;

-	wire	[OPERAND_ADDR_WIDTH-1:0]	sn_addr_next	= sn_addr  + 1'b1;

-	wire	[OPERAND_ADDR_WIDTH-1:0]	r_addr_next	= r_addr  + 1'b1;

-	

-		/* handy stop flags */

-	wire	a_addr_done			= (a_addr      == bram_addr_last)     ? 1'b1 : 1'b0;

-	wire	b_addr_done			= (b_addr      == bram_addr_last)     ? 1'b1 : 1'b0;

-	wire	n_coeff_addr_done	= (n_coeff_addr  == bram_addr_last)     ? 1'b1 : 1'b0;

-	wire	n_addr_done			= (n_addr      == bram_addr_last)     ? 1'b1 : 1'b0;

-	wire	ab_addr_ext_done	= (ab_addr_ext == bram_addr_ext_last) ? 1'b1 : 1'b0;

-	wire	q_addr_done			= (q_addr      == bram_addr_last)     ? 1'b1 : 1'b0;

-	wire	qn_addr_ext_done	= (qn_addr_ext     == bram_addr_ext_last)     ? 1'b1 : 1'b0;

-	wire	s_addr_done	= (s_addr     == bram_addr_last)     ? 1'b1 : 1'b0;

-	wire	sn_addr_done	= (sn_addr     == bram_addr_last)     ? 1'b1 : 1'b0;

-	wire	r_addr_done	= (r_addr     == bram_addr_last)     ? 1'b1 : 1'b0;

-

-		/* delayed B address */

-	reg	[OPERAND_ADDR_WIDTH-1:0]	b_addr_dly;

-	always @(posedge clk) b_addr_dly <= b_addr;

-

-	reg	[OPERAND_ADDR_WIDTH-1:0]	n_coeff_addr_dly;

-	always @(posedge clk) n_coeff_addr_dly <= n_coeff_addr;

-

-	reg	[OPERAND_ADDR_WIDTH-1:0]	n_addr_dly;

-	always @(posedge clk) n_addr_dly <= n_addr;

-				

-		/* map registers to top-level ports */

-	assign a_bram_addr = a_addr;

-	assign b_bram_addr = b_addr;

-	assign n_coeff_bram_addr = n_coeff_addr;

-	assign n_bram_addr = n_addr;

-	assign r_bram_addr = r_addr;

-

-

-		//

-		// Flag

-		//

-	reg	flag_select_s;

-	

-	

-		//

-		// Memory Address Control Logic

-		//

-	always @(posedge clk) begin

-		//

-		case (fsm_next_state)

-			FSM_STATE_LOAD_B_START:				b_addr <= bram_addr_zero;

-			FSM_STATE_LOAD_N_COEFF_START:		n_coeff_addr <= bram_addr_zero;

-			FSM_STATE_LOAD_N_START:				n_addr <= bram_addr_zero;

 			

-			FSM_STATE_LOAD_B_SHIFT:				b_addr <= b_addr_next;

-			FSM_STATE_LOAD_N_COEFF_SHIFT:		n_coeff_addr <= n_coeff_addr_next;

-			FSM_STATE_LOAD_N_SHIFT:				n_addr <= n_addr_next;

-		endcase

-		//

-		case (fsm_state)

-			FSM_STATE_MULT_Q_N_RELOAD: 

-				if (qn_addr_ext == {1'b0, bram_addr_last})

-					n_addr		<= bram_addr_zero;

-				else if (qn_addr_ext > {1'b0, bram_addr_last})

-					n_addr		<= n_addr_next;

+		// handy values
+	wire	[SYSTOLIC_ARRAY_POWER-1:0]	load_mult_cnt_zero = {SYSTOLIC_ARRAY_POWER{1'b0}};
+	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	load_syst_cnt_zero = {SYSTOLIC_CNTR_WIDTH{1'b0}};
+

+	wire	[SYSTOLIC_ARRAY_POWER-1:0]	load_mult_cnt_last = {SYSTOLIC_ARRAY_POWER{1'b1}};	
+	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	load_syst_cnt_last = n_num_words_latch[OPERAND_ADDR_WIDTH-1:SYSTOLIC_ARRAY_POWER];
+	
+		// counter
+	reg	[SYSTOLIC_ARRAY_POWER-1:0]	load_mult_cnt;
+	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	load_syst_cnt;
+	
+		// handy increment value and stop flag
+	wire	[SYSTOLIC_ARRAY_POWER-1:0]	load_mult_cnt_next	= load_mult_cnt + 1'b1;
+	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	load_syst_cnt_next	= load_syst_cnt + 1'b1;
+

+	wire										load_mult_cnt_done	= (load_mult_cnt == load_mult_cnt_last) ? 1'b1 : 1'b0;
+	wire										load_syst_cnt_done	= (load_syst_cnt == load_syst_cnt_last) ? 1'b1 : 1'b0;
 			

-		endcase

-		//

-		case (fsm_state)

-			FSM_STATE_SAVE_START:	r_addr <= bram_addr_zero;

-			FSM_STATE_SAVE_WRITE:	r_addr <= r_addr_next;

-		endcase

-		//

-		case (fsm_next_state)

-			FSM_STATE_MULT_A_B_START:	a_addr <= bram_addr_zero;

-			FSM_STATE_MULT_A_B_RELOAD:	a_addr <= !a_addr_done ? a_addr_next : a_addr;

-		endcase

-		//

-	end

-	

-	

-		//

-		// Internal Memories

-		//

-

-		/* memory inputs */

-	reg	[31: 0]	ab_data_in;

-	reg	[31: 0]	q_data_in;

-	reg	[31: 0]	qn_data_in;

-	wire	[31: 0]	s_data_in;

-	wire	[31: 0]	sn_data_in;

-	reg	[31: 0]	r_data_in;

-

-		/* memory outputs */

-	wire	[31: 0]	ab_data_out;

-	wire	[31: 0]	q_data_out;

-	wire	[31: 0]	qn_data_out;

-	wire	[31: 0]	s_data_out;

-	wire	[31: 0]	sn_data_out;

-

-		/* write enables */

-	reg	ab_wren;

-	reg	q_wren;

-	reg	qn_wren;

-	reg	s_wren;

-	reg	sn_wren;

-	reg	r_wren;

-	

-		/* map */

-	assign r_bram_in = r_data_in;

-	assign r_bram_wr = r_wren;

-

-	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH+1))

-	bram_ab (.clk(clk), .a_addr(ab_addr_ext), .a_wr(ab_wren), .a_in(ab_data_in), .a_out(ab_data_out));

-

-	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH))

-	bram_q (.clk(clk), .a_addr(q_addr), .a_wr(q_wren), .a_in(q_data_in), .a_out(q_data_out));

-	

-	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH+1))

-	bram_qn (.clk(clk), .a_addr(qn_addr_ext), .a_wr(qn_wren), .a_in(qn_data_in), .a_out(qn_data_out));

-

-	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH))

-	bram_s (.clk(clk), .a_addr(s_addr), .a_wr(s_wren), .a_in(s_data_in), .a_out(s_data_out));

-

-	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH))

-	bram_sn (.clk(clk), .a_addr(sn_addr), .a_wr(sn_wren), .a_in(sn_data_in), .a_out(sn_data_out));

-

-	

-		//

-		// Wide Operand Loader

-		//

-	integer j;

-	

-		/* shift logic */

-	always @(posedge clk)

-		//

-		case (fsm_state)

-			//

-			FSM_STATE_LOAD_B_SHIFT: begin

-		

-						/* update the rightmost part of loader buffer */

-				loader_din[SYSTOLIC_ARRAY_LENGTH-1] <= (b_addr_dly <= bram_addr_last) ? b_bram_out : {32{1'b0}};

-				

-						/* shift the loader buffer to the left */

-				for (j=1; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_din[j-1] <= loader_din[j];

-					

-			end

-			//

-			FSM_STATE_LOAD_N_COEFF_SHIFT: begin

-		

-						/* update the rightmost part of loader buffer */

-				loader_din[SYSTOLIC_ARRAY_LENGTH-1] <= (n_coeff_addr_dly <= bram_addr_last) ? n_coeff_bram_out : {32{1'b0}};

-				

-						/* shift the loader buffer to the left */

-				for (j=1; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_din[j-1] <= loader_din[j];

-					

-			end

-			//

-			FSM_STATE_LOAD_N_SHIFT: begin

 		

-						/* update the rightmost part of loader buffer */

-				loader_din[SYSTOLIC_ARRAY_LENGTH-1] <= (n_addr_dly <= bram_addr_last) ? n_bram_out : {32{1'b0}};

+		/*
+		 * Loader Count Logic
+		 */
+	always @(posedge clk) begin
+		//
+		case (fsm_state)
+			FSM_STATE_LOAD_START:	{load_syst_cnt, load_mult_cnt} <= {load_syst_cnt_zero, load_mult_cnt_zero};

+			//
+			FSM_STATE_LOAD_SHIFT:	load_mult_cnt <= load_mult_cnt_next;
+			FSM_STATE_LOAD_WRITE:	load_syst_cnt <= !load_syst_cnt_done ? load_syst_cnt_next : load_syst_cnt;
+		endcase
+		//
+	end
+			

 				

-						/* shift the loader buffer to the left */

-				for (j=1; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_din[j-1] <= loader_din[j];

-					

-			end					

-			//

-		endcase

-		

-

-		/* write enable logic */

-	always @(posedge clk)

-		//

-		case (fsm_next_state)

-		

-			FSM_STATE_LOAD_B_WRITE,

-			FSM_STATE_LOAD_N_COEFF_WRITE,

-			FSM_STATE_LOAD_N_WRITE:

-				//

-				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_wren[j] <= 1'b1;

-					

-			default:

-				//

-				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_wren[j] <= 1'b0;

-					

-		endcase

-

-		/* loader address update logic */

-	always @(posedge clk) begin

-		//

-		case (fsm_state)

-		

-			FSM_STATE_LOAD_B_START,

-			FSM_STATE_LOAD_N_COEFF_START,

-			FSM_STATE_LOAD_N_START:

-				//

-				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_addr_lsb[j] <= syst_cnt_zero;

-					

-			FSM_STATE_LOAD_B_WRITE,

-			FSM_STATE_LOAD_N_COEFF_WRITE,

-			FSM_STATE_LOAD_N_WRITE:

-				//

-				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_addr_lsb[j] <= !syst_cnt_init_done ? syst_cnt_init_next : syst_cnt_init;

-					

-		endcase

-		//

-		case (fsm_next_state)

-			FSM_STATE_MULT_A_B_START,

-			FSM_STATE_MULT_AB_N_COEFF_START,

-			FSM_STATE_MULT_Q_N_START,

-			FSM_STATE_MULT_A_B_RELOAD,

-			FSM_STATE_MULT_AB_N_COEFF_RELOAD,

-			FSM_STATE_MULT_Q_N_RELOAD:

-				//

-				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_addr_lsb[j] <= syst_cnt_zero;

-													

-			FSM_STATE_MULT_A_B_CRUNCH,

-			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,

-			FSM_STATE_MULT_Q_N_CRUNCH:

-				//

-				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_addr_lsb[j] <= !syst_cnt_load_done ? syst_cnt_load_next : syst_cnt_init;

-		endcase

-		//

-		case (fsm_next_state)

-		

-			FSM_STATE_LOAD_B_START,

-			FSM_STATE_MULT_A_B_START:

-				//

-				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_addr_msb[j] <= LOADER_ADDR_MSB_B;

-

-			FSM_STATE_LOAD_N_COEFF_START,

-			FSM_STATE_MULT_AB_N_COEFF_START:

-				//

-				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_addr_msb[j] <= LOADER_ADDR_MSB_N_COEFF;

-					

-			FSM_STATE_LOAD_N_START,

-			FSM_STATE_MULT_Q_N_START:

-				//

-				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-					loader_addr_msb[j] <= LOADER_ADDR_MSB_N;

-

-		endcase

-		//

-	end

-	

-	

-		//

-		// Systolic Array of Processing Elements

-		//

-	reg	[31: 0]	pe_a        [0:SYSTOLIC_ARRAY_LENGTH-1];

-	reg	[31: 0]	pe_b        [0:SYSTOLIC_ARRAY_LENGTH-1];

-	wire	[31: 0]	pe_t        [0:SYSTOLIC_ARRAY_LENGTH-1];

-	wire	[31: 0]	pe_c_in     [0:SYSTOLIC_ARRAY_LENGTH-1];

-	wire	[31: 0]	pe_p        [0:SYSTOLIC_ARRAY_LENGTH-1];

-	wire	[31: 0]	pe_c_out    [0:SYSTOLIC_ARRAY_LENGTH-1];

-	reg	[31: 0]	pe_c_out_dly[0:SYSTOLIC_ARRAY_LENGTH-1];

-	

-

-		//

-		// These can be turned into a FIFO (maybe later?)...

-		//

-	//reg	[31: 0]	pe_c_out_mem[0:SYSTOLIC_ARRAY_LENGTH-1][0:SYSTOLIC_NUM_CYCLES-1];

-	//reg	[31: 0]	pe_t_mem    [0:SYSTOLIC_ARRAY_LENGTH-1][0:SYSTOLIC_NUM_CYCLES-1];

-

-	reg	fifo_c_rst;

-	reg	fifo_t_rst;

-

-	wire	fifo_c_wren;

-	wire	fifo_c_rden;

-	

-	wire	fifo_t_wren;

-	wire	fifo_t_rden;

-		

-	wire	[32 * SYSTOLIC_ARRAY_LENGTH - 1 : 0]	fifo_c_din;

-	wire	[32 * SYSTOLIC_ARRAY_LENGTH - 1 : 0]	fifo_c_dout;

-	

-	wire	[32 * SYSTOLIC_ARRAY_LENGTH - 1 : 0]	fifo_t_din;

-	wire	[32 * SYSTOLIC_ARRAY_LENGTH - 1 : 0]	fifo_t_dout;

-	

-	/**/

-	modexpa7_simple_fifo #

-	(

-		.BUS_WIDTH	(32 * SYSTOLIC_ARRAY_LENGTH),

-		.DEPTH_BITS	(SYSTOLIC_CNTR_WIDTH)

-	)

-	fifo_c

-	(

-		.clk			(clk),

-		.rst			(fifo_c_rst),

-		.wr_en		(fifo_c_wren),

-		.d_in			(fifo_c_din),

-		.rd_en		(fifo_c_rden),

-		.d_out		(fifo_c_dout)

-	);

-	

-	modexpa7_simple_fifo #

-	(

-		.BUS_WIDTH	(32 * SYSTOLIC_ARRAY_LENGTH),

-		.DEPTH_BITS	(SYSTOLIC_CNTR_WIDTH)

-	)

-	fifo_t

-	(

-		.clk			(clk),

-		.rst			(fifo_t_rst),

-		.wr_en		(fifo_t_wren),

-		.d_in			(fifo_t_din),

-		.rd_en		(fifo_t_rden),

-		.d_out		(fifo_t_dout)

-	);

-	

-	generate for (i=0; i<SYSTOLIC_ARRAY_LENGTH; i=i+1)

-		begin : modexpa7_systolic_pe_multiplier		

-			modexpa7_systolic_pe systolic_pe_inst

-			(

-				.clk		(clk),

-				.a			(pe_a[i]),

-				.b			(pe_b[i]),

-				.t			(pe_t[i]),

-				.c_in		(pe_c_in[i]),

-				.p			(pe_p[i]),

-				.c_out	(pe_c_out[i])

-			);

-			assign pe_c_in[i] = fifo_c_dout[32 * (i + 1) - 1 -: 32];

-			assign pe_t[i] = fifo_t_dout[32 * (i + 1) - 1 -: 32];

-			assign fifo_c_din[32 * (i + 1) - 1 -: 32] = pe_c_out_dly[i];

-			always @(posedge clk) pe_c_out_dly[i] <= pe_c_out[i];

-		end

+		/*
+		 * Wide Operand Loader
+		 */
+	
+		/*
+		 * Explain how parallelized loader works here...
+		 *
+		 */
+	
+	
+		// loader input
+	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	loader_addr[0:SYSTOLIC_ARRAY_LENGTH-1];
+	reg										loader_wren[0:SYSTOLIC_ARRAY_LENGTH-1];
+	reg	[                 32-1:0]	loader_din [0:SYSTOLIC_ARRAY_LENGTH-1];
+	
+		// loader output
+	wire	[                 32-1:0]	loader_dout[0:SYSTOLIC_ARRAY_LENGTH-1];
+			
+		// generate parallelized loader		
+	genvar i;
+	generate for (i=0; i<SYSTOLIC_ARRAY_LENGTH; i=i+1)
+		//
+		begin : gen_bram_1rw_readfirst_loader
+			//
+			bram_1rw_readfirst #
+			(
+				.MEM_WIDTH		(32),
+				.MEM_ADDR_BITS	(SYSTOLIC_CNTR_WIDTH)
+			)
+			bram_loader
+			(
+				.clk		(clk),
+				.a_addr	(loader_addr[i]),
+				.a_wr		(loader_wren[i]),
+				.a_in		(loader_din[i]),
+				.a_out	(loader_dout[i])
+			);
+			//
+		end
+		//
 	endgenerate

-

-

-

-		

 			

-			//

-			// Shift Registers

-			//

-	reg	[SYSTOLIC_NUM_CYCLES-1:0]	shreg_load;

-	reg	[SYSTOLIC_PE_LATENCY  :0]	shreg_latency;

-	reg	[SYSTOLIC_NUM_CYCLES-1:0]	shreg_unload;

-

-	wire	shreg_done_load = shreg_load[syst_cnt_last];

-	wire	shreg_done_latency = shreg_latency[SYSTOLIC_PE_LATENCY];

-	wire	shreg_done_unload = shreg_unload[syst_cnt_last];

-

-	reg										shreg_now_loading;

-	reg										shreg_now_latency;

-	reg										shreg_now_unloading;

-	

-	reg										shreg_done_latency_dly;

-	

-	always @(posedge clk)

-		shreg_done_latency_dly <= shreg_done_latency;

-

-	always @(posedge clk)

-		//

-		case (fsm_state)

-			FSM_STATE_LOAD_N_FINAL: begin

-				shreg_load		<= {{SYSTOLIC_NUM_CYCLES-1{1'b0}}, 1'b0};

-				shreg_latency	<= {{SYSTOLIC_PE_LATENCY{1'b0}}, 1'b0};

-				shreg_unload	<= {{SYSTOLIC_NUM_CYCLES-1{1'b0}}, 1'b0};

-			end

-			//

-			FSM_STATE_MULT_A_B_START,

-			FSM_STATE_MULT_AB_N_COEFF_START,

-			FSM_STATE_MULT_Q_N_START,

-			FSM_STATE_MULT_A_B_RELOAD,

-			FSM_STATE_MULT_AB_N_COEFF_RELOAD,

-			FSM_STATE_MULT_Q_N_RELOAD: begin

-				shreg_now_loading	<= 1'b1;

-				shreg_now_latency <= 1'b1;

-				shreg_now_unloading <= 1'b0;

-				shreg_load		<= {{SYSTOLIC_NUM_CYCLES-1{1'b0}}, 1'b1};

-				shreg_latency	<= {{SYSTOLIC_PE_LATENCY{1'b0}}, 1'b1};

-				shreg_unload	<= {{SYSTOLIC_NUM_CYCLES-1{1'b0}}, 1'b0};

-			end

-			//

-			FSM_STATE_MULT_A_B_CRUNCH,

-			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,

-			FSM_STATE_MULT_Q_N_CRUNCH: begin

-				shreg_load		<= {shreg_load[SYSTOLIC_NUM_CYCLES-2:0], 1'b0};

-				shreg_latency	<= {shreg_latency[SYSTOLIC_PE_LATENCY-1:0], 1'b0};

-				shreg_unload	<= {shreg_unload[SYSTOLIC_NUM_CYCLES-2:0], shreg_latency[SYSTOLIC_PE_LATENCY]};

-				

-				if (shreg_done_load) shreg_now_loading <= 1'b0;

-				if (shreg_done_latency) shreg_now_latency <= 1'b0;

-				if (shreg_done_latency) shreg_now_unloading <= 1'b1;

-				else if (shreg_done_unload) shreg_now_unloading <= 1'b0;

 				

-			end

-			//

-			default: begin

-				shreg_now_loading <= 1'b0;

-				shreg_now_latency <= 1'b0;

-				shreg_now_unloading <= 1'b0;

-			end

-			//

-		endcase

-		

-		

-	always @(posedge clk)

-		//

-		case (fsm_state)

-			FSM_STATE_MULT_A_B_START,

-			FSM_STATE_MULT_AB_N_COEFF_START,

-			FSM_STATE_MULT_Q_N_START:			fifo_c_rst <= 1'b1;

-			

-			FSM_STATE_MULT_A_B_CRUNCH,

-			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,

-			FSM_STATE_MULT_Q_N_CRUNCH:		if (shreg_done_load)	fifo_c_rst <= 1'b0;

-		endcase

-

-	always @(posedge clk)

-		//

-		case (fsm_state)

-			FSM_STATE_MULT_A_B_START,

-			FSM_STATE_MULT_AB_N_COEFF_START,

-			FSM_STATE_MULT_Q_N_START:			fifo_t_rst <= 1'b1;

-			

-			FSM_STATE_MULT_A_B_CRUNCH,

-			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,

-			FSM_STATE_MULT_Q_N_CRUNCH:		if (shreg_done_load)	fifo_t_rst <= 1'b0;

-		endcase

-

-

-	reg	[32 * (SYSTOLIC_ARRAY_LENGTH - 1) - 1 : 0]	pe_p_msb_dly;

-	

-	always @(posedge clk)

-		//

-		for (j=1; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-			pe_p_msb_dly[32 * j - 1 -: 32] <= pe_p[j];

-			

-	wire	[31: 0]	pe_p_lsb_masked = shreg_now_unloading ? pe_p[0] : 32'd0;

-	assign fifo_t_din = {pe_p_lsb_masked, pe_p_msb_dly};

+		/*
+		 * Block Memory Addresses
+		 */
+		
+		/*
+		 * Explain why there are two memory sizes.
+		 */
+		
+		// the very first addresses
+	wire	[OPERAND_ADDR_WIDTH-1:0]	bram_addr_zero			= {      {OPERAND_ADDR_WIDTH{1'b0}}};
+	wire	[OPERAND_ADDR_WIDTH  :0]	bram_addr_ext_zero	= {1'b0, {OPERAND_ADDR_WIDTH{1'b0}}};
+	
+		// the very last addresses
+	wire	[OPERAND_ADDR_WIDTH-1:0]	bram_addr_last     = {n_num_words_latch};
+	wire	[OPERAND_ADDR_WIDTH  :0]	bram_addr_ext_last = {n_num_words_latch, 1'b1};
+
+		// address registers
+	reg	[OPERAND_ADDR_WIDTH-1:0]	b_addr;
+		
+		// handy increment values
+	wire	[OPERAND_ADDR_WIDTH-1:0]	b_addr_next		= b_addr       + 1'b1;
+	
+		// handy stop flags
+	wire	b_addr_done			= (b_addr      == bram_addr_last)     ? 1'b1 : 1'b0;
+
+		// delayed addresses
+	reg	[OPERAND_ADDR_WIDTH-1:0]	b_addr_dly;

+		
+	always @(posedge clk) b_addr_dly <= b_addr;
+
+				
+		// map registers to top-level ports
+	assign b_bram_addr = b_addr;
 

-	

-	

-	reg shreg_now_unloading_dly;

-	always @(posedge clk)

-		shreg_now_unloading_dly <= shreg_now_unloading;

-	

-	assign fifo_c_wren = shreg_now_unloading_dly;

-	assign fifo_c_rden = shreg_now_loading;

-	

-	assign fifo_t_wren = shreg_now_unloading_dly;	

-	assign fifo_t_rden = shreg_now_loading;

-	

-	

-		

-		

-	always @(posedge clk) begin

-		//

-		case (fsm_state)

-			FSM_STATE_MULT_A_B_START:				ab_addr_ext		<= bram_addr_ext_zero;

-			FSM_STATE_MULT_AB_N_COEFF_START:		q_addr			<= bram_addr_zero;

-			FSM_STATE_MULT_Q_N_START: begin		qn_addr_ext		<= bram_addr_ext_zero;

-															ab_addr_ext		<= bram_addr_ext_zero;															

-															end

-			

-			FSM_STATE_MULT_A_B_RELOAD:				ab_addr_ext		<= ab_addr_ext_next;

-			FSM_STATE_MULT_AB_N_COEFF_RELOAD:	q_addr			<= q_addr_next;

-			FSM_STATE_MULT_Q_N_RELOAD: begin		qn_addr_ext		<= qn_addr_ext_next;

-															ab_addr_ext		<= ab_addr_ext_next;

-															end

-		endcase

-		//

-		case (fsm_state)

-		

-			FSM_STATE_MULT_Q_N_RELOAD: begin

-				if (qn_addr_ext == {1'b0, bram_addr_last}) begin

-					s_addr		<= bram_addr_zero;

-					sn_addr	<= bram_addr_zero;

-				end

 				

-				if ((qn_addr_ext > {1'b0, bram_addr_last}) && (qn_addr_ext < bram_addr_ext_last)) begin

-					s_addr <= s_addr_next;

-					sn_addr <= sn_addr_next;

-				end

-

-				if (qn_addr_ext == bram_addr_ext_last) begin

-					s_addr <= bram_addr_zero;

-					sn_addr <= bram_addr_zero;

-				end

-			

-			end

-			

-			FSM_STATE_MULT_Q_N_FINAL,

-			FSM_STATE_SAVE_START,

-			FSM_STATE_SAVE_WRITE: begin

-				s_addr <= !s_addr_done ? s_addr_next : s_addr;

-				sn_addr <= !sn_addr_done ? sn_addr_next : sn_addr;

+		/*
+		 * Loader Data Input 
+		 */
+	integer j;
+	
+		// shift logic
+	always @(posedge clk)
+		//
+		case (fsm_state)
+			//
+			FSM_STATE_LOAD_SHIFT: begin
+		
+						// update the rightmost part of loader buffer
+				loader_din[SYSTOLIC_ARRAY_LENGTH-1] <= (b_addr_dly <= bram_addr_last) ? b_bram_out : {32{1'b0}};
+				
+						// shift the loader buffer to the left
+				for (j=1; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_din[j-1] <= loader_din[j];
+					
 			end

-			

-		endcase

-		

-		//

-		case (fsm_next_state)

-			FSM_STATE_MULT_AB_N_COEFF_START:		ab_addr_ext <= bram_addr_ext_zero;

-			FSM_STATE_MULT_AB_N_COEFF_RELOAD:	ab_addr_ext <= ab_addr_ext_next;

-		endcase

-		//

-		case (fsm_next_state)

-			FSM_STATE_MULT_Q_N_START:		q_addr <= bram_addr_zero;

-			FSM_STATE_MULT_Q_N_RELOAD:		q_addr <= !q_addr_done ? q_addr_next : q_addr;

-		endcase

+			//			

+		endcase
 

-		//

-	end

-		

-	always @(posedge clk) begin

-		//

-		if (fsm_state == FSM_STATE_MULT_A_B_CRUNCH) begin

-			ab_wren <= shreg_done_latency_dly;

-			ab_data_in <= shreg_done_latency_dly ? pe_p[0] : 32'hXXXXXXXX;

-		end else begin

-			ab_wren <= 1'b0;

-			ab_data_in <= 32'hXXXXXXXX;

-		end

-		//

-		if (fsm_state == FSM_STATE_MULT_AB_N_COEFF_CRUNCH) begin

-			q_wren <= shreg_done_latency_dly;

-			q_data_in <= shreg_done_latency_dly ? pe_p[0] : 32'hXXXXXXXX;

-		end else begin

-			q_wren <= 1'b0;

-			q_data_in <= 32'hXXXXXXXX;

-		end

-		//

-		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH) begin

-			qn_wren <= shreg_done_latency_dly;

-			qn_data_in <= shreg_done_latency_dly ? pe_p[0] : 32'hXXXXXXXX;

-		end else begin

-			qn_wren <= 1'b0;

-			qn_data_in <= 32'hXXXXXXXX;

-		end		

-		//

-		case (fsm_state)

-			FSM_STATE_SAVE_START:	r_wren <= 1'b1;

-			FSM_STATE_SAVE_WRITE:	r_wren <= ~r_addr_done;

-			default:						r_wren <= 1'b0;

-		endcase

-		//

-	end

-	

-	

-	always @(posedge clk)

-		//

-		case (fsm_next_state)

-			FSM_STATE_MULT_A_B_START,

-			FSM_STATE_MULT_AB_N_COEFF_START,

-			FSM_STATE_MULT_Q_N_START,

-			FSM_STATE_MULT_A_B_RELOAD,

-			FSM_STATE_MULT_AB_N_COEFF_RELOAD,

-			FSM_STATE_MULT_Q_N_RELOAD:

-				//

-				syst_cnt_load <= syst_cnt_zero;

-			

-			FSM_STATE_MULT_A_B_CRUNCH,

-			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,

-			FSM_STATE_MULT_Q_N_CRUNCH:

+

+		/*

+		 * Load Write Enable Logic

+		 */
+	always @(posedge clk)
+		//
+		case (fsm_next_state)
+		
+			FSM_STATE_LOAD_WRITE:

 				//

-				syst_cnt_load <= !syst_cnt_load_done ? syst_cnt_load_next : syst_cnt_load;

-				

+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_wren[j] <= 1'b1;
+					
+			default:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_wren[j] <= 1'b0;
+					
 		endcase

 

-		

-		

-	always @(posedge clk)

-		//

-		case (fsm_state)

-			FSM_STATE_MULT_A_B_CRUNCH,

-			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,

-			FSM_STATE_MULT_Q_N_CRUNCH: begin

-		

-			if (shreg_done_latency)	syst_cnt_unload <= syst_cnt_zero;

-			else if (shreg_now_unloading)

-				syst_cnt_unload <= !syst_cnt_unload_done ? syst_cnt_unload_next : syst_cnt_unload;

-

-			end

-		endcase

-	

-	/*

-	always @(posedge clk)

-		//

-		case (fsm_state)

-			FSM_STATE_MULT_A_B_CRUNCH,

-			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,

-			FSM_STATE_MULT_Q_N_CRUNCH: begin

-		

-				//if (shreg_now_unloading)

-					//for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-						//pe_c_out_mem[j][syst_cnt_unload] <= pe_c_out[j];

-						

-				if (shreg_now_unloading) begin

-				

-					for (j=1; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-						pe_t_mem[j-1][syst_cnt_unload] <= pe_p[j];

-						

-					if (syst_cnt_unload > syst_cnt_zero)

-						pe_t_mem[SYSTOLIC_ARRAY_LENGTH-1][syst_cnt_unload-1'b1] <= pe_p[0];

-					else

-						pe_t_mem[SYSTOLIC_ARRAY_LENGTH-1][syst_cnt_last] <= 32'd0;

-					

-				end

-			end

-		endcase

-		*/

 

-		

-			//

-			// T and C_IN can be moved to a separate code block

-			//

-	always @(posedge clk) begin

-		//

-		if (fsm_state == FSM_STATE_MULT_A_B_CRUNCH)

-			//

-			for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-				//

-				if (shreg_now_loading) begin

-					pe_a[j]		<= (ab_addr_ext > {1'b0, a_addr}) ? 32'd0 : a_bram_out;

-					pe_b[j]		<= loader_dout[j];

-					//pe_t[j]		<= (a_addr == bram_addr_zero) ? 32'd0 : pe_t_mem[j][syst_cnt_load_dly];

-					//pe_c_in[j]	<= (a_addr == bram_addr_zero) ? 32'd0 : pe_c_out_mem[j][syst_cnt_load_dly];

-				end else begin

-					pe_a[j]		<= 32'hXXXXXXXX;				

-					pe_b[j]		<= 32'hXXXXXXXX;

-					//pe_t[j]		<= 32'hXXXXXXXX;

-					//pe_c_in[j]	<= 32'hXXXXXXXX;

-				end

-		//

-		if (fsm_state == FSM_STATE_MULT_AB_N_COEFF_CRUNCH)

-			//

-			for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-				//

-				if (shreg_now_loading) begin

-					pe_a[j]		<= ab_data_out;

-					pe_b[j]		<= loader_dout[j];

-					//pe_t[j]		<= (ab_addr_ext == bram_addr_ext_zero) ? 32'd0 : pe_t_mem[j][syst_cnt_load_dly];

-					//pe_c_in[j]	<= (ab_addr_ext == bram_addr_ext_zero) ? 32'd0 : pe_c_out_mem[j][syst_cnt_load_dly];

-				end else begin

-					pe_a[j]		<= 32'hXXXXXXXX;				

-					pe_b[j]		<= 32'hXXXXXXXX;

-					//pe_t[j]		<= 32'hXXXXXXXX;

-					//pe_c_in[j]	<= 32'hXXXXXXXX;

-				end

-		//

-		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH)

-			//

-			for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)

-				//

-				if (shreg_now_loading) begin

-					pe_a[j]		<= (qn_addr_ext > {1'b0, q_addr}) ? 32'd0 : q_data_out;

-					pe_b[j]		<= loader_dout[j];

-					//pe_t[j]		<= (q_addr == bram_addr_zero) ? 32'd0 : pe_t_mem[j][syst_cnt_load_dly];

-					//pe_c_in[j]	<= (q_addr == bram_addr_zero) ? 32'd0 : pe_c_out_mem[j][syst_cnt_load_dly];

-				end else begin

-					pe_a[j]		<= 32'hXXXXXXXX;				

-					pe_b[j]		<= 32'hXXXXXXXX;

-					//pe_t[j]		<= 32'hXXXXXXXX;

-					//pe_c_in[j]	<= 32'hXXXXXXXX;

-				end

-		//

-	

-		//

-	end

-		

-		

-		//

-		// Adder

-		//

 		/*

-		 * This adder is used to calculate S = AB + QN.

-		 *

+		 * Loader Address Update Logic

 		 */

-	reg				add1_ce;					// clock enable

-	reg	[31: 0]	add1_s;					// sum output

-	wire				add1_c_in;				// carry input

-	wire	[31: 0]	add1_a;					// A-input

-	reg	[31: 0]	add1_b;					// B-input

-	reg				add1_c_in_mask;		// flag to not carry anything into the very first word

-	reg				add1_c_out;				// carry output

-	

-		/* add masking into carry feedback chain */

-	assign add1_c_in = add1_c_out & ~add1_c_in_mask;

-

-		/* mask carry for the very first word of N */

-	//always @(posedge clk) add1_c_in_mask <= (fsm_next_state == FSM_STATE_INIT_2) ? 1'b1 : 1'b0;

+
+	always @(posedge clk)
+		//
+		case (fsm_state)
+		
+			FSM_STATE_LOAD_START:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_addr[j] <= load_syst_cnt_zero;
+					
+			FSM_STATE_LOAD_WRITE:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_addr[j] <= !load_syst_cnt_done ? load_syst_cnt_next : load_syst_cnt;
+					
+		endcase
 	

-	always @(posedge  clk)

-		//

-		if (add1_ce)

-			//

-			{add1_c_out, add1_s} <= {{1{1'b0}}, add1_a} + {{1{1'b0}}, add1_b} + {{32{1'b0}}, add1_c_in};

-	

-	assign add1_a = qn_data_in;

-	

-	always @(posedge clk)

-		//

-		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH)

-			add1_b <= shreg_done_latency_dly ? ab_data_out : 32'hXXXXXXXX;

-		else

-			add1_b <= 32'hXXXXXXXX;

-

-	always @(posedge clk)

-		//

-		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH)

-			add1_c_in_mask <= (shreg_done_latency_dly && (ab_addr_ext == bram_addr_ext_zero)) ? 1'b1 : 1'b0;

-		else

-			add1_c_in_mask <= 1'b0;

-

-	always @(posedge clk)

-		//

-		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH)

-			add1_ce <= shreg_done_latency_dly;

-		else

-			add1_ce <= 1'b0;

 

-

-	assign s_data_in = add1_s;

-	assign sn_data_in = sub1_d;

-	

-	always @(posedge clk) begin

-		//

-		s_wren <= add1_ce;

-		sn_wren <= sub1_ce;

-	end

-		

-		

-		

-		//

-		// Subtractor

-		//

 		/*

-		 * This subtractor is used to calculate SN = S - N.

-		 *

+		 * Memory Address Control Logic

 		 */

-	reg				sub1_ce;					// clock enable

-	reg	[31: 0]	sub1_d;					// difference output

-	wire				sub1_b_in;				// borrow input

-	wire	[31: 0]	sub1_a;					// A-input

-	reg	[31: 0]	sub1_b;					// B-input

-	reg				sub1_b_in_mask;		// flag to not borrow anything from the very first word

-	reg				sub1_b_out;				// borrow output

-	

-		/* add masking into borrow feedback chain */

-	assign sub1_b_in = sub1_b_out & ~sub1_b_in_mask;

-	

-	always @(posedge  clk)

-		//

-		if (sub1_ce)

-			//

-			{sub1_b_out, sub1_d} <= {{1{1'b0}}, sub1_a} - {{1{1'b0}}, sub1_b} - {{32{1'b0}}, sub1_b_in};

-	

-	assign sub1_a = add1_s;

-	

-	always @(posedge clk)

-		//

-		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH)

-			sub1_b <= add1_ce ? n_bram_out : 32'hXXXXXXXX;

-		else

-			sub1_b <= 32'hXXXXXXXX;

-

-	always @(posedge clk)

-		//

-		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH)

-			sub1_b_in_mask <= (add1_ce && ((qn_addr_ext - 1'b1) == {1'b0, bram_addr_last})) ? 1'b1 : 1'b0;

-		else

-			sub1_b_in_mask <= 1'b0;

-

-	always @(posedge clk)

-		//

-		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH)

-			sub1_ce <= add1_ce && (qn_addr_ext > {1'b0, q_addr});

-		else

-			sub1_ce <= 1'b0;

-

-

-	assign s_data_in = add1_s;

-	

-	always @(posedge clk)

-		//

-		s_wren <= add1_ce;

-		

-		

-

-	always @(posedge clk)

-		//

-		if (fsm_state == FSM_STATE_MULT_Q_N_FINAL)

-			flag_select_s <= sub1_b_out & ~add1_c_out;

-		

-

-	always @(posedge clk)

-		//

-		case (fsm_state)

-			FSM_STATE_SAVE_START,

-			FSM_STATE_SAVE_WRITE:

-				r_data_in <= flag_select_s ? s_data_out : sn_data_out;

-		endcase

-

-		

-			

-		//

-		// FSM Process

-		//

-	always @(posedge clk or negedge rst_n)

-		//

-		if (rst_n == 1'b0)	fsm_state <= FSM_STATE_IDLE;

-		else						fsm_state <= fsm_next_state;

-	

-	

-		//

-		// FSM Transition Logic

-		//

-	always @* begin

-		//

-		fsm_next_state = FSM_STATE_STOP;

-		//

-		case (fsm_state)

-

-			FSM_STATE_IDLE:				if (ena_trig)				fsm_next_state = FSM_STATE_LOAD_B_START;

-												else							fsm_next_state = FSM_STATE_IDLE;

-			//

-			FSM_STATE_LOAD_B_START:											fsm_next_state = FSM_STATE_LOAD_B_SHIFT;

-			FSM_STATE_LOAD_B_SHIFT:		if (mult_cnt_done)			fsm_next_state = FSM_STATE_LOAD_B_WRITE;

-												else								fsm_next_state = FSM_STATE_LOAD_B_SHIFT;

-			FSM_STATE_LOAD_B_WRITE:		if (syst_cnt_init_done)		fsm_next_state = FSM_STATE_LOAD_B_FINAL;

-												else							fsm_next_state = FSM_STATE_LOAD_B_SHIFT;

-			FSM_STATE_LOAD_B_FINAL:										fsm_next_state = FSM_STATE_LOAD_N_COEFF_START;

-			//

-			FSM_STATE_LOAD_N_COEFF_START:											fsm_next_state = FSM_STATE_LOAD_N_COEFF_SHIFT;

-			FSM_STATE_LOAD_N_COEFF_SHIFT:		if (mult_cnt_done)			fsm_next_state = FSM_STATE_LOAD_N_COEFF_WRITE;

-												else								fsm_next_state = FSM_STATE_LOAD_N_COEFF_SHIFT;

-			FSM_STATE_LOAD_N_COEFF_WRITE:		if (syst_cnt_init_done)		fsm_next_state = FSM_STATE_LOAD_N_COEFF_FINAL;

-												else							fsm_next_state = FSM_STATE_LOAD_N_COEFF_SHIFT;

-			FSM_STATE_LOAD_N_COEFF_FINAL:										fsm_next_state = FSM_STATE_LOAD_N_START;

-			//

-			FSM_STATE_LOAD_N_START:											fsm_next_state = FSM_STATE_LOAD_N_SHIFT;

-			FSM_STATE_LOAD_N_SHIFT:		if (mult_cnt_done)			fsm_next_state = FSM_STATE_LOAD_N_WRITE;

-												else								fsm_next_state = FSM_STATE_LOAD_N_SHIFT;

-			FSM_STATE_LOAD_N_WRITE:		if (syst_cnt_init_done)		fsm_next_state = FSM_STATE_LOAD_N_FINAL;

-												else							fsm_next_state = FSM_STATE_LOAD_N_SHIFT;

-			FSM_STATE_LOAD_N_FINAL:										fsm_next_state = FSM_STATE_MULT_A_B_START;

-			//

-			FSM_STATE_MULT_A_B_START:									fsm_next_state = FSM_STATE_MULT_A_B_CRUNCH;

-			FSM_STATE_MULT_A_B_CRUNCH:	if (shreg_done_unload)	fsm_next_state = FSM_STATE_MULT_A_B_RELOAD;

-												else							fsm_next_state = FSM_STATE_MULT_A_B_CRUNCH;

-			FSM_STATE_MULT_A_B_RELOAD:	if (ab_addr_ext_done)	fsm_next_state = FSM_STATE_MULT_A_B_FINAL;

-												else							fsm_next_state = FSM_STATE_MULT_A_B_CRUNCH;

-			FSM_STATE_MULT_A_B_FINAL:									fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_START;

-			//

-			FSM_STATE_MULT_AB_N_COEFF_START:									fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_CRUNCH;

-			FSM_STATE_MULT_AB_N_COEFF_CRUNCH:	if (shreg_done_unload)	fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_RELOAD;

-															else							fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_CRUNCH;

-			FSM_STATE_MULT_AB_N_COEFF_RELOAD:	if (q_addr_done)	fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_FINAL;

-															else							fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_CRUNCH;

-			FSM_STATE_MULT_AB_N_COEFF_FINAL:									fsm_next_state = FSM_STATE_MULT_Q_N_START;

-			//

-			FSM_STATE_MULT_Q_N_START:									fsm_next_state = FSM_STATE_MULT_Q_N_CRUNCH;

-			FSM_STATE_MULT_Q_N_CRUNCH:	if (shreg_done_unload)	fsm_next_state = FSM_STATE_MULT_Q_N_RELOAD;

-															else							fsm_next_state = FSM_STATE_MULT_Q_N_CRUNCH;

-			FSM_STATE_MULT_Q_N_RELOAD:	if (qn_addr_ext_done)	fsm_next_state = FSM_STATE_MULT_Q_N_FINAL;

-															else							fsm_next_state = FSM_STATE_MULT_Q_N_CRUNCH;

-			FSM_STATE_MULT_Q_N_FINAL:									fsm_next_state = FSM_STATE_SAVE_START;

-			//

-			FSM_STATE_SAVE_START:										fsm_next_state = FSM_STATE_SAVE_WRITE;

-			FSM_STATE_SAVE_WRITE:	if (r_addr_done)				fsm_next_state = FSM_STATE_SAVE_FINAL;

-											else								fsm_next_state = FSM_STATE_SAVE_WRITE;

-			FSM_STATE_SAVE_FINAL:										fsm_next_state = FSM_STATE_STOP;

-			//

-			FSM_STATE_STOP:												fsm_next_state = FSM_STATE_IDLE;

-

+	always @(posedge clk) begin
+		//
+		case (fsm_next_state)
+			FSM_STATE_LOAD_START:	b_addr <= bram_addr_zero;
+			FSM_STATE_LOAD_SHIFT:	b_addr <= b_addr_next;
 		endcase

 		//

 	end

 

-

-endmodule

-

-//======================================================================

-// End of file

-//======================================================================

+
+		
+			
+		/*
+		 * FSM Process
+		 */
+	always @(posedge clk or negedge rst_n)
+		//
+		if (rst_n == 1'b0)	fsm_state <= FSM_STATE_IDLE;
+		else						fsm_state <= fsm_next_state;
+	
+	
+		/*
+		 * FSM Transition Logic
+		 */
+	always @* begin
+		//
+		fsm_next_state = FSM_STATE_STOP;
+		//
+		case (fsm_state)
+			//
+			FSM_STATE_IDLE:				if (ena_trig)					fsm_next_state = FSM_STATE_LOAD_START;
+												else								fsm_next_state = FSM_STATE_IDLE;
+			//
+			FSM_STATE_LOAD_START:											fsm_next_state = FSM_STATE_LOAD_SHIFT;
+			FSM_STATE_LOAD_SHIFT:		if (load_mult_cnt_done)		fsm_next_state = FSM_STATE_LOAD_WRITE;
+												else								fsm_next_state = FSM_STATE_LOAD_SHIFT;
+			FSM_STATE_LOAD_WRITE:		if (load_syst_cnt_done)		fsm_next_state = FSM_STATE_LOAD_FINAL;
+												else								fsm_next_state = FSM_STATE_LOAD_SHIFT;
+			FSM_STATE_LOAD_FINAL:											fsm_next_state = FSM_STATE_STOP;
+			//

+			//FSM_STATE_MULT_START:
+			//FSM_STATE_MULT_CRUNCH:
+			//FSM_STATE_MULT_FINAL:
+			//
+			FSM_STATE_STOP:												fsm_next_state = FSM_STATE_IDLE;
+			//
+		endcase
+		//
+	end
+
+
+endmodule
+
+//======================================================================
+// End of file
+//======================================================================
diff --git a/src/rtl/modexpa7_systolic_multiplier_old.v b/src/rtl/modexpa7_systolic_multiplier_old.v
new file mode 100644
index 0000000..8b00370
--- /dev/null
+++ b/src/rtl/modexpa7_systolic_multiplier_old.v
@@ -0,0 +1,1260 @@
+//======================================================================
+//
+// modexpa7_systolic_multiplier.v
+// -----------------------------------------------------------------------------
+// Systolic Montgomery multiplier.
+//
+// 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_systolic_multiplier #
+	(
+			//
+			// This sets the address widths of memory buffers. Internal data
+			// width is 32 bits, so for e.g. 2048-bit operands buffers must store
+			// 2048 / 32 = 64 words, and these need 6-bit address bus, because
+			// 2 ** 6 = 64.
+			//
+		parameter	OPERAND_ADDR_WIDTH		= 4,
+		
+			//
+			// Explain.
+			//
+		parameter	SYSTOLIC_ARRAY_POWER		= 1
+	)
+	(
+		input											clk,
+		input											rst_n,
+
+		input											ena,
+		output										rdy,
+
+		output	[OPERAND_ADDR_WIDTH-1:0]	a_bram_addr,
+		output	[OPERAND_ADDR_WIDTH-1:0]	b_bram_addr,
+		output	[OPERAND_ADDR_WIDTH-1:0]	n_bram_addr,
+		output	[OPERAND_ADDR_WIDTH-1:0]	n_coeff_bram_addr,
+		output	[OPERAND_ADDR_WIDTH-1:0]	r_bram_addr,
+
+		input		[                32-1:0]	a_bram_out,
+		input		[                32-1:0]	b_bram_out,
+		input		[                32-1:0]	n_bram_out,
+		input		[                32-1:0]	n_coeff_bram_out,
+
+		output	[                32-1:0]	r_bram_in,
+		output										r_bram_wr,
+
+		input		[OPERAND_ADDR_WIDTH-1:0]	ab_num_words
+	);
+	
+		
+		//
+		// Include Settings
+		//
+	`include "pe/modexpa7_primitive_switch.v"
+	`include "modexpa7_settings.v"
+		
+
+		//
+		// FSM Declaration
+		//
+	localparam	[ 7: 0]	FSM_STATE_IDLE								= 8'h00;
+
+	localparam	[ 7: 0]	FSM_STATE_LOAD_B_START					= 8'h11;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_B_SHIFT					= 8'h12;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_B_WRITE					= 8'h13;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_B_FINAL					= 8'h14;
+
+	localparam	[ 7: 0]	FSM_STATE_LOAD_N_COEFF_START			= 8'h21;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_N_COEFF_SHIFT			= 8'h22;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_N_COEFF_WRITE			= 8'h23;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_N_COEFF_FINAL			= 8'h24;
+
+	localparam	[ 7: 0]	FSM_STATE_LOAD_N_START					= 8'h31;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_N_SHIFT					= 8'h32;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_N_WRITE					= 8'h33;
+	localparam	[ 7: 0]	FSM_STATE_LOAD_N_FINAL					= 8'h34;
+
+	localparam	[ 7: 0]	FSM_STATE_MULT_A_B_START				= 8'h41;
+	localparam	[ 7: 0]	FSM_STATE_MULT_A_B_CRUNCH				= 8'h42;
+	localparam	[ 7: 0]	FSM_STATE_MULT_A_B_RELOAD				= 8'h43;
+	localparam	[ 7: 0]	FSM_STATE_MULT_A_B_FINAL				= 8'h44;
+
+	localparam	[ 7: 0]	FSM_STATE_MULT_AB_N_COEFF_START		= 8'h51;
+	localparam	[ 7: 0]	FSM_STATE_MULT_AB_N_COEFF_CRUNCH		= 8'h52;
+	localparam	[ 7: 0]	FSM_STATE_MULT_AB_N_COEFF_RELOAD		= 8'h53;
+	localparam	[ 7: 0]	FSM_STATE_MULT_AB_N_COEFF_FINAL		= 8'h54;
+
+	localparam	[ 7: 0]	FSM_STATE_MULT_Q_N_START				= 8'h61;
+	localparam	[ 7: 0]	FSM_STATE_MULT_Q_N_CRUNCH				= 8'h62;
+	localparam	[ 7: 0]	FSM_STATE_MULT_Q_N_ADD_S				= 8'h63;
+	localparam	[ 7: 0]	FSM_STATE_MULT_Q_N_SUB_SN				= 8'h64;
+	localparam	[ 7: 0]	FSM_STATE_MULT_Q_N_RELOAD				= 8'h65;
+	localparam	[ 7: 0]	FSM_STATE_MULT_Q_N_FINAL				= 8'h66;
+	
+	localparam	[ 7: 0]	FSM_STATE_SAVE_START						= 8'h71;
+	localparam	[ 7: 0]	FSM_STATE_SAVE_WRITE						= 8'h72;
+	localparam	[ 7: 0]	FSM_STATE_SAVE_FINAL						= 8'h73;	
+	
+	localparam	[ 7: 0]	FSM_STATE_STOP								= 8'hFF;
+	
+		//
+		// FSM State / Next State
+		//
+	reg	[ 7: 0]	fsm_state = FSM_STATE_IDLE;
+	reg	[ 7: 0]	fsm_next_state;
+
+
+		//
+		// Enable Delay and Trigger
+		//
+   reg ena_dly = 1'b0;
+	
+		/* delay enable by one clock cycle */
+   always @(posedge clk) ena_dly <= ena;
+
+		/* trigger new operation when enable goes high */
+   wire ena_trig = ena && !ena_dly;
+	
+	
+		//
+		// Ready Flag Logic
+		//
+	reg rdy_reg = 1'b1;
+	assign rdy = rdy_reg;
+
+   always @(posedge clk or negedge rst_n)
+		
+			/* reset flag */
+		if (rst_n == 1'b0) rdy_reg <= 1'b1;
+		else begin
+		
+				/* clear flag when operation is started */
+			if (fsm_state == FSM_STATE_IDLE)	rdy_reg <= ~ena_trig;
+			
+				/* set flag after operation is finished */
+			if (fsm_state == FSM_STATE_STOP)	rdy_reg <= 1'b1;			
+			
+		end
+		
+		
+		//
+		// Parameters Latch
+		//
+	reg	[OPERAND_ADDR_WIDTH-1:0]	ab_num_words_latch;
+
+		/* save number of words in a and b when new operation starts */
+	always @(posedge clk)
+		//
+		if (fsm_next_state == FSM_STATE_LOAD_B_START)
+			ab_num_words_latch <= ab_num_words;
+			
+			
+		//
+		// Systolic Cycle Counters
+		//
+		
+		/* handy values */
+	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_zero = {SYSTOLIC_CNTR_WIDTH{1'b0}};
+	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_last = ab_num_words_latch[OPERAND_ADDR_WIDTH-1:SYSTOLIC_ARRAY_POWER];
+	
+		/* counters */
+	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_init;
+	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_load;
+	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_unload;
+		
+		/* handy increment values */
+	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_init_next		= syst_cnt_init   + 1'b1;
+	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_load_next		= syst_cnt_load   + 1'b1;
+	wire	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_unload_next		= syst_cnt_unload + 1'b1;
+
+		/* handy stop flags */
+	wire										syst_cnt_init_done		= (syst_cnt_init   == syst_cnt_last) ? 1'b1 : 1'b0;
+	wire										syst_cnt_load_done		= (syst_cnt_load   == syst_cnt_last) ? 1'b1 : 1'b0;
+	wire										syst_cnt_unload_done		= (syst_cnt_unload == syst_cnt_last) ? 1'b1 : 1'b0;
+
+		/* delayed load counter */
+	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	syst_cnt_load_dly;
+	always @(posedge clk) syst_cnt_load_dly <= syst_cnt_load;
+
+
+		//
+		// Multiplier Iteration Counter
+		//
+		
+		/* handy values */
+	wire	[SYSTOLIC_ARRAY_POWER-1:0]	mult_cnt_zero = {SYSTOLIC_ARRAY_POWER{1'b0}};
+	wire	[SYSTOLIC_ARRAY_POWER-1:0]	mult_cnt_last = {SYSTOLIC_ARRAY_POWER{1'b1}};
+	
+		/* counter */
+	reg	[SYSTOLIC_ARRAY_POWER-1:0]	mult_cnt;
+	
+		/* handy increment value and stop flag */
+	wire	[SYSTOLIC_ARRAY_POWER-1:0]	mult_cnt_next = mult_cnt + 1'b1;
+	wire										mult_cnt_done = (mult_cnt == mult_cnt_last) ? 1'b1 : 1'b0;
+			
+			
+		//
+		// Initialization Counter Control Logic
+		//
+	always @(posedge clk) begin
+		//
+		case (fsm_state)
+			FSM_STATE_LOAD_B_START,
+			FSM_STATE_LOAD_N_COEFF_START,
+			FSM_STATE_LOAD_N_START:				mult_cnt <= mult_cnt_zero;
+			
+			FSM_STATE_LOAD_B_SHIFT,
+			FSM_STATE_LOAD_N_COEFF_SHIFT,
+			FSM_STATE_LOAD_N_SHIFT:				mult_cnt <= mult_cnt_next;
+		endcase
+		//
+		case (fsm_state)
+			FSM_STATE_LOAD_B_START,
+			FSM_STATE_LOAD_N_COEFF_START,
+			FSM_STATE_LOAD_N_START:				syst_cnt_init <= syst_cnt_zero;
+			
+			FSM_STATE_LOAD_B_WRITE,
+			FSM_STATE_LOAD_N_COEFF_WRITE,
+			FSM_STATE_LOAD_N_WRITE:				syst_cnt_init <= !syst_cnt_init_done ? syst_cnt_init_next : syst_cnt_init;
+		endcase
+		//
+	end
+	
+	
+		//
+		// Operand Loader
+		//
+	
+		/*
+		 * Explain how parallelized loader works here...
+		 *
+		 */
+	
+		/* loader banks */
+	localparam	[ 1: 0]	LOADER_ADDR_MSB_B				= 2'd0;
+	localparam	[ 1: 0]	LOADER_ADDR_MSB_N_COEFF		= 2'd1;
+	localparam	[ 1: 0]	LOADER_ADDR_MSB_N				= 2'd2;
+	
+		/* loader input */
+	reg	[                  2-1:0]	loader_addr_msb[0:SYSTOLIC_ARRAY_LENGTH-1];	
+	reg	[SYSTOLIC_CNTR_WIDTH-1:0]	loader_addr_lsb[0:SYSTOLIC_ARRAY_LENGTH-1];
+	reg										loader_wren    [0:SYSTOLIC_ARRAY_LENGTH-1];
+	reg	[                 32-1:0]	loader_din     [0:SYSTOLIC_ARRAY_LENGTH-1];
+	
+		/* loader output */
+	wire	[                 32-1:0]	loader_dout    [0:SYSTOLIC_ARRAY_LENGTH-1];
+			
+		/* generate parallelized loader */
+		
+		//
+		// Loader currently stores B, N_COEFF and N, it can be coded another way
+		// to initially store B, then AB, then Q. Some memory can be saved thay way.
+		// Maybe later...
+		//
+		
+	genvar i;
+	generate for (i=0; i<SYSTOLIC_ARRAY_LENGTH; i=i+1)
+		//
+		begin : gen_bram_1rw_readfirst_loader
+			//
+			bram_1rw_readfirst #
+			(
+				.MEM_WIDTH		(32),
+				.MEM_ADDR_BITS	(SYSTOLIC_CNTR_WIDTH + 2)
+			)
+			bram_loader
+			(
+				.clk		(clk),
+				.a_addr	({loader_addr_msb[i], loader_addr_lsb[i]}),
+				.a_wr		(loader_wren[i]),
+				.a_in		(loader_din[i]),
+				.a_out	(loader_dout[i])
+			);
+			//
+		end
+		//
+	endgenerate
+	
+
+		//
+		// Block Memory Addresses
+		//
+		
+		/*
+		 * Explain why there are two memory sizes.
+		 *
+		 */
+		
+		/* the very first addresses */
+	wire	[OPERAND_ADDR_WIDTH-1:0]	bram_addr_zero			= {      {OPERAND_ADDR_WIDTH{1'b0}}};
+	wire	[OPERAND_ADDR_WIDTH  :0]	bram_addr_ext_zero	= {1'b0, {OPERAND_ADDR_WIDTH{1'b0}}};
+	
+		/* the very last addresses */
+	wire	[OPERAND_ADDR_WIDTH-1:0]	bram_addr_last     = {ab_num_words_latch};
+	wire	[OPERAND_ADDR_WIDTH  :0]	bram_addr_ext_last = {ab_num_words_latch, 1'b1};
+
+		/* address registers */
+	reg	[OPERAND_ADDR_WIDTH-1:0]	a_addr;
+	reg	[OPERAND_ADDR_WIDTH-1:0]	b_addr;
+	reg	[OPERAND_ADDR_WIDTH-1:0]	n_coeff_addr;
+	reg	[OPERAND_ADDR_WIDTH-1:0]	n_addr;
+	reg	[OPERAND_ADDR_WIDTH  :0]	ab_addr_ext;
+	reg	[OPERAND_ADDR_WIDTH-1:0]	q_addr;
+	reg	[OPERAND_ADDR_WIDTH  :0]	qn_addr_ext;
+	reg	[OPERAND_ADDR_WIDTH-1:0]	s_addr;
+	reg	[OPERAND_ADDR_WIDTH-1:0]	sn_addr;
+	reg	[OPERAND_ADDR_WIDTH-1:0]	r_addr;
+		
+		/* handy increment values */
+	wire	[OPERAND_ADDR_WIDTH-1:0]	a_addr_next			= a_addr       + 1'b1;
+	wire	[OPERAND_ADDR_WIDTH-1:0]	b_addr_next			= b_addr       + 1'b1;
+	wire	[OPERAND_ADDR_WIDTH-1:0]	n_coeff_addr_next	= n_coeff_addr + 1'b1;
+	wire	[OPERAND_ADDR_WIDTH-1:0]	n_addr_next			= n_addr       + 1'b1;
+	wire	[OPERAND_ADDR_WIDTH  :0]	ab_addr_ext_next	= ab_addr_ext  + 1'b1;
+	wire	[OPERAND_ADDR_WIDTH-1:0]	q_addr_next			= q_addr       + 1'b1;
+	wire	[OPERAND_ADDR_WIDTH  :0]	qn_addr_ext_next	= qn_addr_ext  + 1'b1;
+	wire	[OPERAND_ADDR_WIDTH-1:0]	s_addr_next			= s_addr       + 1'b1;
+	wire	[OPERAND_ADDR_WIDTH-1:0]	sn_addr_next		= sn_addr      + 1'b1;
+	wire	[OPERAND_ADDR_WIDTH-1:0]	r_addr_next			= r_addr       + 1'b1;
+	
+		/* handy stop flags */
+	wire	a_addr_done			= (a_addr      == bram_addr_last)     ? 1'b1 : 1'b0;
+	wire	b_addr_done			= (b_addr      == bram_addr_last)     ? 1'b1 : 1'b0;
+	wire	n_coeff_addr_done	= (n_coeff_addr  == bram_addr_last)     ? 1'b1 : 1'b0;
+	wire	n_addr_done			= (n_addr      == bram_addr_last)     ? 1'b1 : 1'b0;
+	wire	ab_addr_ext_done	= (ab_addr_ext == bram_addr_ext_last) ? 1'b1 : 1'b0;
+	wire	q_addr_done			= (q_addr      == bram_addr_last)     ? 1'b1 : 1'b0;
+	wire	qn_addr_ext_done	= (qn_addr_ext     == bram_addr_ext_last)     ? 1'b1 : 1'b0;
+	wire	s_addr_done	= (s_addr     == bram_addr_last)     ? 1'b1 : 1'b0;
+	wire	sn_addr_done	= (sn_addr     == bram_addr_last)     ? 1'b1 : 1'b0;
+	wire	r_addr_done	= (r_addr     == bram_addr_last)     ? 1'b1 : 1'b0;
+
+		/* delayed B address */
+	reg	[OPERAND_ADDR_WIDTH-1:0]	b_addr_dly;
+	always @(posedge clk) b_addr_dly <= b_addr;
+
+	reg	[OPERAND_ADDR_WIDTH-1:0]	n_coeff_addr_dly;
+	always @(posedge clk) n_coeff_addr_dly <= n_coeff_addr;
+
+	reg	[OPERAND_ADDR_WIDTH-1:0]	n_addr_dly;
+	always @(posedge clk) n_addr_dly <= n_addr;
+				
+		/* map registers to top-level ports */
+	assign a_bram_addr = a_addr;
+	assign b_bram_addr = b_addr;
+	assign n_coeff_bram_addr = n_coeff_addr;
+	assign n_bram_addr = n_addr;
+	assign r_bram_addr = r_addr;
+
+
+		//
+		// Flag
+		//
+	reg	flag_select_s;
+	
+	
+		//
+		// Memory Address Control Logic
+		//
+	always @(posedge clk) begin
+		//
+		case (fsm_next_state)
+			FSM_STATE_LOAD_B_START:				b_addr <= bram_addr_zero;
+			FSM_STATE_LOAD_N_COEFF_START:		n_coeff_addr <= bram_addr_zero;
+			FSM_STATE_LOAD_N_START:				n_addr <= bram_addr_zero;
+			
+			FSM_STATE_LOAD_B_SHIFT:				b_addr <= b_addr_next;
+			FSM_STATE_LOAD_N_COEFF_SHIFT:		n_coeff_addr <= n_coeff_addr_next;
+			FSM_STATE_LOAD_N_SHIFT:				n_addr <= n_addr_next;
+		endcase
+		//
+		case (fsm_state)
+			FSM_STATE_MULT_Q_N_RELOAD: 
+				if (qn_addr_ext == {1'b0, bram_addr_last})
+					n_addr		<= bram_addr_zero;
+				else if (qn_addr_ext > {1'b0, bram_addr_last})
+					n_addr		<= n_addr_next;
+			
+		endcase
+		//
+		case (fsm_state)
+			FSM_STATE_SAVE_START:	r_addr <= bram_addr_zero;
+			FSM_STATE_SAVE_WRITE:	r_addr <= r_addr_next;
+		endcase
+		//
+		case (fsm_next_state)
+			FSM_STATE_MULT_A_B_START:	a_addr <= bram_addr_zero;
+			FSM_STATE_MULT_A_B_RELOAD:	a_addr <= !a_addr_done ? a_addr_next : a_addr;
+		endcase
+		//
+	end
+	
+	
+		//
+		// Internal Memories
+		//
+
+		/* memory inputs */
+	reg	[31: 0]	ab_data_in;
+	reg	[31: 0]	q_data_in;
+	reg	[31: 0]	qn_data_in;
+	wire	[31: 0]	s_data_in;
+	wire	[31: 0]	sn_data_in;
+	reg	[31: 0]	r_data_in;
+
+		/* memory outputs */
+	wire	[31: 0]	ab_data_out;
+	wire	[31: 0]	q_data_out;
+	wire	[31: 0]	qn_data_out;
+	wire	[31: 0]	s_data_out;
+	wire	[31: 0]	sn_data_out;
+
+		/* write enables */
+	reg	ab_wren;
+	reg	q_wren;
+	reg	qn_wren;
+	reg	s_wren;
+	reg	sn_wren;
+	reg	r_wren;
+	
+		/* map */
+	assign r_bram_in = r_data_in;
+	assign r_bram_wr = r_wren;
+
+	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH+1))
+	bram_ab (.clk(clk), .a_addr(ab_addr_ext), .a_wr(ab_wren), .a_in(ab_data_in), .a_out(ab_data_out));
+
+	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH))
+	bram_q (.clk(clk), .a_addr(q_addr), .a_wr(q_wren), .a_in(q_data_in), .a_out(q_data_out));
+	
+	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH+1))
+	bram_qn (.clk(clk), .a_addr(qn_addr_ext), .a_wr(qn_wren), .a_in(qn_data_in), .a_out(qn_data_out));
+
+	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH))
+	bram_s (.clk(clk), .a_addr(s_addr), .a_wr(s_wren), .a_in(s_data_in), .a_out(s_data_out));
+
+	bram_1rw_readfirst #(.MEM_WIDTH(32), .MEM_ADDR_BITS(OPERAND_ADDR_WIDTH))
+	bram_sn (.clk(clk), .a_addr(sn_addr), .a_wr(sn_wren), .a_in(sn_data_in), .a_out(sn_data_out));
+
+	
+		//
+		// Wide Operand Loader
+		//
+	integer j;
+	
+		/* shift logic */
+	always @(posedge clk)
+		//
+		case (fsm_state)
+			//
+			FSM_STATE_LOAD_B_SHIFT: begin
+		
+						/* update the rightmost part of loader buffer */
+				loader_din[SYSTOLIC_ARRAY_LENGTH-1] <= (b_addr_dly <= bram_addr_last) ? b_bram_out : {32{1'b0}};
+				
+						/* shift the loader buffer to the left */
+				for (j=1; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_din[j-1] <= loader_din[j];
+					
+			end
+			//
+			FSM_STATE_LOAD_N_COEFF_SHIFT: begin
+		
+						/* update the rightmost part of loader buffer */
+				loader_din[SYSTOLIC_ARRAY_LENGTH-1] <= (n_coeff_addr_dly <= bram_addr_last) ? n_coeff_bram_out : {32{1'b0}};
+				
+						/* shift the loader buffer to the left */
+				for (j=1; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_din[j-1] <= loader_din[j];
+					
+			end
+			//
+			FSM_STATE_LOAD_N_SHIFT: begin
+		
+						/* update the rightmost part of loader buffer */
+				loader_din[SYSTOLIC_ARRAY_LENGTH-1] <= (n_addr_dly <= bram_addr_last) ? n_bram_out : {32{1'b0}};
+				
+						/* shift the loader buffer to the left */
+				for (j=1; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_din[j-1] <= loader_din[j];
+					
+			end					
+			//
+		endcase
+		
+
+		/* write enable logic */
+	always @(posedge clk)
+		//
+		case (fsm_next_state)
+		
+			FSM_STATE_LOAD_B_WRITE,
+			FSM_STATE_LOAD_N_COEFF_WRITE,
+			FSM_STATE_LOAD_N_WRITE:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_wren[j] <= 1'b1;
+					
+			default:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_wren[j] <= 1'b0;
+					
+		endcase
+
+		/* loader address update logic */
+	always @(posedge clk) begin
+		//
+		case (fsm_state)
+		
+			FSM_STATE_LOAD_B_START,
+			FSM_STATE_LOAD_N_COEFF_START,
+			FSM_STATE_LOAD_N_START:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_addr_lsb[j] <= syst_cnt_zero;
+					
+			FSM_STATE_LOAD_B_WRITE,
+			FSM_STATE_LOAD_N_COEFF_WRITE,
+			FSM_STATE_LOAD_N_WRITE:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_addr_lsb[j] <= !syst_cnt_init_done ? syst_cnt_init_next : syst_cnt_init;
+					
+		endcase
+		//
+		case (fsm_next_state)
+			FSM_STATE_MULT_A_B_START,
+			FSM_STATE_MULT_AB_N_COEFF_START,
+			FSM_STATE_MULT_Q_N_START,
+			FSM_STATE_MULT_A_B_RELOAD,
+			FSM_STATE_MULT_AB_N_COEFF_RELOAD,
+			FSM_STATE_MULT_Q_N_RELOAD:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_addr_lsb[j] <= syst_cnt_zero;
+													
+			FSM_STATE_MULT_A_B_CRUNCH,
+			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,
+			FSM_STATE_MULT_Q_N_CRUNCH:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_addr_lsb[j] <= !syst_cnt_load_done ? syst_cnt_load_next : syst_cnt_init;
+		endcase
+		//
+		case (fsm_next_state)
+		
+			FSM_STATE_LOAD_B_START,
+			FSM_STATE_MULT_A_B_START:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_addr_msb[j] <= LOADER_ADDR_MSB_B;
+
+			FSM_STATE_LOAD_N_COEFF_START,
+			FSM_STATE_MULT_AB_N_COEFF_START:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_addr_msb[j] <= LOADER_ADDR_MSB_N_COEFF;
+					
+			FSM_STATE_LOAD_N_START,
+			FSM_STATE_MULT_Q_N_START:
+				//
+				for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+					loader_addr_msb[j] <= LOADER_ADDR_MSB_N;
+
+		endcase
+		//
+	end
+	
+	
+		//
+		// Systolic Array of Processing Elements
+		//
+	reg	[31: 0]	pe_a        [0:SYSTOLIC_ARRAY_LENGTH-1];
+	reg	[31: 0]	pe_b        [0:SYSTOLIC_ARRAY_LENGTH-1];
+	wire	[31: 0]	pe_t        [0:SYSTOLIC_ARRAY_LENGTH-1];
+	wire	[31: 0]	pe_c_in     [0:SYSTOLIC_ARRAY_LENGTH-1];
+	wire	[31: 0]	pe_p        [0:SYSTOLIC_ARRAY_LENGTH-1];
+	wire	[31: 0]	pe_c_out    [0:SYSTOLIC_ARRAY_LENGTH-1];
+	reg	[31: 0]	pe_c_out_dly[0:SYSTOLIC_ARRAY_LENGTH-1];
+	
+
+		//
+		// These can be turned into a FIFO (maybe later?)...
+		//
+	//reg	[31: 0]	pe_c_out_mem[0:SYSTOLIC_ARRAY_LENGTH-1][0:SYSTOLIC_NUM_CYCLES-1];
+	//reg	[31: 0]	pe_t_mem    [0:SYSTOLIC_ARRAY_LENGTH-1][0:SYSTOLIC_NUM_CYCLES-1];
+
+	reg	fifo_c_rst;
+	reg	fifo_t_rst;
+
+	wire	fifo_c_wren;
+	wire	fifo_c_rden;
+	
+	wire	fifo_t_wren;
+	wire	fifo_t_rden;
+		
+	wire	[32 * SYSTOLIC_ARRAY_LENGTH - 1 : 0]	fifo_c_din;
+	wire	[32 * SYSTOLIC_ARRAY_LENGTH - 1 : 0]	fifo_c_dout;
+	
+	wire	[32 * SYSTOLIC_ARRAY_LENGTH - 1 : 0]	fifo_t_din;
+	wire	[32 * SYSTOLIC_ARRAY_LENGTH - 1 : 0]	fifo_t_dout;
+	
+	/**/
+	modexpa7_simple_fifo #
+	(
+		.BUS_WIDTH	(32 * SYSTOLIC_ARRAY_LENGTH),
+		.DEPTH_BITS	(SYSTOLIC_CNTR_WIDTH)
+	)
+	fifo_c
+	(
+		.clk			(clk),
+		.rst			(fifo_c_rst),
+		.wr_en		(fifo_c_wren),
+		.d_in			(fifo_c_din),
+		.rd_en		(fifo_c_rden),
+		.d_out		(fifo_c_dout)
+	);
+	
+	modexpa7_simple_fifo #
+	(
+		.BUS_WIDTH	(32 * SYSTOLIC_ARRAY_LENGTH),
+		.DEPTH_BITS	(SYSTOLIC_CNTR_WIDTH)
+	)
+	fifo_t
+	(
+		.clk			(clk),
+		.rst			(fifo_t_rst),
+		.wr_en		(fifo_t_wren),
+		.d_in			(fifo_t_din),
+		.rd_en		(fifo_t_rden),
+		.d_out		(fifo_t_dout)
+	);
+	
+	generate for (i=0; i<SYSTOLIC_ARRAY_LENGTH; i=i+1)
+		begin : modexpa7_systolic_pe_multiplier		
+			modexpa7_systolic_pe systolic_pe_inst
+			(
+				.clk		(clk),
+				.a			(pe_a[i]),
+				.b			(pe_b[i]),
+				.t			(pe_t[i]),
+				.c_in		(pe_c_in[i]),
+				.p			(pe_p[i]),
+				.c_out	(pe_c_out[i])
+			);
+			assign pe_c_in[i] = fifo_c_dout[32 * (i + 1) - 1 -: 32];
+			assign pe_t[i] = fifo_t_dout[32 * (i + 1) - 1 -: 32];
+			assign fifo_c_din[32 * (i + 1) - 1 -: 32] = pe_c_out_dly[i];
+			always @(posedge clk) pe_c_out_dly[i] <= pe_c_out[i];
+		end
+	endgenerate
+
+
+
+		
+			
+			//
+			// Shift Registers
+			//
+	reg	[SYSTOLIC_NUM_CYCLES-1:0]	shreg_load;
+	reg	[SYSTOLIC_PE_LATENCY  :0]	shreg_latency;
+	reg	[SYSTOLIC_NUM_CYCLES-1:0]	shreg_unload;
+
+	wire	shreg_done_load = shreg_load[syst_cnt_last];
+	wire	shreg_done_latency = shreg_latency[SYSTOLIC_PE_LATENCY];
+	wire	shreg_done_unload = shreg_unload[syst_cnt_last];
+
+	reg										shreg_now_loading;
+	reg										shreg_now_latency;
+	reg										shreg_now_unloading;
+	
+	reg										shreg_done_latency_dly;
+	
+	always @(posedge clk)
+		shreg_done_latency_dly <= shreg_done_latency;
+
+	always @(posedge clk)
+		//
+		case (fsm_state)
+			FSM_STATE_LOAD_N_FINAL: begin
+				shreg_load		<= {{SYSTOLIC_NUM_CYCLES-1{1'b0}}, 1'b0};
+				shreg_latency	<= {{SYSTOLIC_PE_LATENCY{1'b0}}, 1'b0};
+				shreg_unload	<= {{SYSTOLIC_NUM_CYCLES-1{1'b0}}, 1'b0};
+			end
+			//
+			FSM_STATE_MULT_A_B_START,
+			FSM_STATE_MULT_AB_N_COEFF_START,
+			FSM_STATE_MULT_Q_N_START,
+			FSM_STATE_MULT_A_B_RELOAD,
+			FSM_STATE_MULT_AB_N_COEFF_RELOAD,
+			FSM_STATE_MULT_Q_N_RELOAD: begin
+				shreg_now_loading	<= 1'b1;
+				shreg_now_latency <= 1'b1;
+				shreg_now_unloading <= 1'b0;
+				shreg_load		<= {{SYSTOLIC_NUM_CYCLES-1{1'b0}}, 1'b1};
+				shreg_latency	<= {{SYSTOLIC_PE_LATENCY{1'b0}}, 1'b1};
+				shreg_unload	<= {{SYSTOLIC_NUM_CYCLES-1{1'b0}}, 1'b0};
+			end
+			//
+			FSM_STATE_MULT_A_B_CRUNCH,
+			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,
+			FSM_STATE_MULT_Q_N_CRUNCH: begin
+				shreg_load		<= {shreg_load[SYSTOLIC_NUM_CYCLES-2:0], 1'b0};
+				shreg_latency	<= {shreg_latency[SYSTOLIC_PE_LATENCY-1:0], 1'b0};
+				shreg_unload	<= {shreg_unload[SYSTOLIC_NUM_CYCLES-2:0], shreg_latency[SYSTOLIC_PE_LATENCY]};
+				
+				if (shreg_done_load) shreg_now_loading <= 1'b0;
+				if (shreg_done_latency) shreg_now_latency <= 1'b0;
+				if (shreg_done_latency) shreg_now_unloading <= 1'b1;
+				else if (shreg_done_unload) shreg_now_unloading <= 1'b0;
+				
+			end
+			//
+			default: begin
+				shreg_now_loading <= 1'b0;
+				shreg_now_latency <= 1'b0;
+				shreg_now_unloading <= 1'b0;
+			end
+			//
+		endcase
+		
+		
+	always @(posedge clk)
+		//
+		case (fsm_state)
+			FSM_STATE_MULT_A_B_START,
+			FSM_STATE_MULT_AB_N_COEFF_START,
+			FSM_STATE_MULT_Q_N_START:			fifo_c_rst <= 1'b1;
+			
+			FSM_STATE_MULT_A_B_CRUNCH,
+			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,
+			FSM_STATE_MULT_Q_N_CRUNCH:		if (shreg_done_load)	fifo_c_rst <= 1'b0;
+		endcase
+
+	always @(posedge clk)
+		//
+		case (fsm_state)
+			FSM_STATE_MULT_A_B_START,
+			FSM_STATE_MULT_AB_N_COEFF_START,
+			FSM_STATE_MULT_Q_N_START:			fifo_t_rst <= 1'b1;
+			
+			FSM_STATE_MULT_A_B_CRUNCH,
+			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,
+			FSM_STATE_MULT_Q_N_CRUNCH:		if (shreg_done_load)	fifo_t_rst <= 1'b0;
+		endcase
+
+
+	reg	[32 * (SYSTOLIC_ARRAY_LENGTH - 1) - 1 : 0]	pe_p_msb_dly;
+	
+	always @(posedge clk)
+		//
+		for (j=1; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+			pe_p_msb_dly[32 * j - 1 -: 32] <= pe_p[j];
+			
+	wire	[31: 0]	pe_p_lsb_masked = shreg_now_unloading ? pe_p[0] : 32'd0;
+	assign fifo_t_din = {pe_p_lsb_masked, pe_p_msb_dly};
+
+	
+	
+	reg shreg_now_unloading_dly;
+	always @(posedge clk)
+		shreg_now_unloading_dly <= shreg_now_unloading;
+	
+	assign fifo_c_wren = shreg_now_unloading_dly;
+	assign fifo_c_rden = shreg_now_loading;
+	
+	assign fifo_t_wren = shreg_now_unloading_dly;	
+	assign fifo_t_rden = shreg_now_loading;
+	
+	
+		
+		
+	always @(posedge clk) begin
+		//
+		case (fsm_state)
+			FSM_STATE_MULT_A_B_START:				ab_addr_ext		<= bram_addr_ext_zero;
+			FSM_STATE_MULT_AB_N_COEFF_START:		q_addr			<= bram_addr_zero;
+			FSM_STATE_MULT_Q_N_START: begin		qn_addr_ext		<= bram_addr_ext_zero;
+															ab_addr_ext		<= bram_addr_ext_zero;															
+															end
+			
+			FSM_STATE_MULT_A_B_RELOAD:				ab_addr_ext		<= ab_addr_ext_next;
+			FSM_STATE_MULT_AB_N_COEFF_RELOAD:	q_addr			<= q_addr_next;
+			FSM_STATE_MULT_Q_N_RELOAD: begin		qn_addr_ext		<= qn_addr_ext_next;
+															ab_addr_ext		<= ab_addr_ext_next;
+															end
+		endcase
+		//
+		case (fsm_state)
+			
+			FSM_STATE_MULT_Q_N_RELOAD: begin
+				//
+				if (qn_addr_ext == {1'b0, bram_addr_last}) begin
+					s_addr	<= bram_addr_zero;
+					sn_addr	<= bram_addr_zero;
+				end
+				//
+				if ((qn_addr_ext > {1'b0, bram_addr_last}) && (qn_addr_ext < bram_addr_ext_last)) begin
+					s_addr <= s_addr_next;
+					sn_addr <= sn_addr_next;
+				end
+				//
+				if (qn_addr_ext == bram_addr_ext_last) begin
+					s_addr <= bram_addr_zero;
+					sn_addr <= bram_addr_zero;
+				end
+				//
+			end			
+		//
+		/*
+		case (fsm_state)
+			
+			FSM_STATE_MULT_Q_N_RELOAD: begin
+				if (qn_addr_ext == {1'b0, bram_addr_last}) begin
+					s_addr	<= bram_addr_zero;
+					sn_addr	<= bram_addr_zero;
+				end
+				
+				if ((qn_addr_ext > {1'b0, bram_addr_last}) && (qn_addr_ext < bram_addr_ext_last)) begin
+					s_addr <= s_addr_next;
+					sn_addr <= sn_addr_next;
+				end
+
+				if (qn_addr_ext == bram_addr_ext_last) begin
+					s_addr <= bram_addr_zero;
+					sn_addr <= bram_addr_zero;
+				end
+			
+			end
+			
+			FSM_STATE_MULT_Q_N_FINAL,
+			FSM_STATE_SAVE_START,
+			FSM_STATE_SAVE_WRITE: begin
+				s_addr <= !s_addr_done ? s_addr_next : s_addr;
+				sn_addr <= !sn_addr_done ? sn_addr_next : sn_addr;
+			end
+			*/
+		endcase
+		
+		//
+		case (fsm_next_state)
+			FSM_STATE_MULT_AB_N_COEFF_START:		ab_addr_ext <= bram_addr_ext_zero;
+			FSM_STATE_MULT_AB_N_COEFF_RELOAD:	ab_addr_ext <= ab_addr_ext_next;
+		endcase
+		//
+		case (fsm_next_state)
+			FSM_STATE_MULT_Q_N_START:		q_addr <= bram_addr_zero;
+			FSM_STATE_MULT_Q_N_RELOAD:		q_addr <= !q_addr_done ? q_addr_next : q_addr;
+		endcase
+
+		//
+	end
+		
+	always @(posedge clk) begin
+		//
+		if (fsm_state == FSM_STATE_MULT_A_B_CRUNCH) begin
+			ab_wren <= shreg_done_latency_dly;
+			ab_data_in <= shreg_done_latency_dly ? pe_p[0] : 32'hXXXXXXXX;
+		end else begin
+			ab_wren <= 1'b0;
+			ab_data_in <= 32'hXXXXXXXX;
+		end
+		//
+		if (fsm_state == FSM_STATE_MULT_AB_N_COEFF_CRUNCH) begin
+			q_wren <= shreg_done_latency_dly;
+			q_data_in <= shreg_done_latency_dly ? pe_p[0] : 32'hXXXXXXXX;
+		end else begin
+			q_wren <= 1'b0;
+			q_data_in <= 32'hXXXXXXXX;
+		end
+		//
+		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH) begin
+			qn_wren <= shreg_done_latency_dly;
+			qn_data_in <= shreg_done_latency_dly ? pe_p[0] : 32'hXXXXXXXX;
+		end else begin
+			qn_wren <= 1'b0;
+			qn_data_in <= 32'hXXXXXXXX;
+		end		
+		//
+		case (fsm_state)
+			FSM_STATE_SAVE_START:	r_wren <= 1'b1;
+			FSM_STATE_SAVE_WRITE:	r_wren <= ~r_addr_done;
+			default:						r_wren <= 1'b0;
+		endcase
+		//
+	end
+	
+	
+	always @(posedge clk)
+		//
+		case (fsm_next_state)
+			FSM_STATE_MULT_A_B_START,
+			FSM_STATE_MULT_AB_N_COEFF_START,
+			FSM_STATE_MULT_Q_N_START,
+			FSM_STATE_MULT_A_B_RELOAD,
+			FSM_STATE_MULT_AB_N_COEFF_RELOAD,
+			FSM_STATE_MULT_Q_N_RELOAD:
+				//
+				syst_cnt_load <= syst_cnt_zero;
+			
+			FSM_STATE_MULT_A_B_CRUNCH,
+			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,
+			FSM_STATE_MULT_Q_N_CRUNCH:
+				//
+				syst_cnt_load <= !syst_cnt_load_done ? syst_cnt_load_next : syst_cnt_load;
+				
+		endcase
+
+		
+		
+	always @(posedge clk)
+		//
+		case (fsm_state)
+			FSM_STATE_MULT_A_B_CRUNCH,
+			FSM_STATE_MULT_AB_N_COEFF_CRUNCH,
+			FSM_STATE_MULT_Q_N_CRUNCH: begin
+		
+			if (shreg_done_latency)	syst_cnt_unload <= syst_cnt_zero;
+			else if (shreg_now_unloading)
+				syst_cnt_unload <= !syst_cnt_unload_done ? syst_cnt_unload_next : syst_cnt_unload;
+
+			end
+		endcase
+	
+		
+			//
+			// T and C_IN can be moved to a separate code block
+			//
+	always @(posedge clk) begin
+		//
+		if (fsm_state == FSM_STATE_MULT_A_B_CRUNCH)
+			//
+			for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+				//
+				if (shreg_now_loading) begin
+					pe_a[j]		<= (ab_addr_ext > {1'b0, a_addr}) ? 32'd0 : a_bram_out;
+					pe_b[j]		<= loader_dout[j];
+					//pe_t[j]		<= (a_addr == bram_addr_zero) ? 32'd0 : pe_t_mem[j][syst_cnt_load_dly];
+					//pe_c_in[j]	<= (a_addr == bram_addr_zero) ? 32'd0 : pe_c_out_mem[j][syst_cnt_load_dly];
+				end else begin
+					pe_a[j]		<= 32'hXXXXXXXX;				
+					pe_b[j]		<= 32'hXXXXXXXX;
+					//pe_t[j]		<= 32'hXXXXXXXX;
+					//pe_c_in[j]	<= 32'hXXXXXXXX;
+				end
+		//
+		if (fsm_state == FSM_STATE_MULT_AB_N_COEFF_CRUNCH)
+			//
+			for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+				//
+				if (shreg_now_loading) begin
+					pe_a[j]		<= ab_data_out;
+					pe_b[j]		<= loader_dout[j];
+					//pe_t[j]		<= (ab_addr_ext == bram_addr_ext_zero) ? 32'd0 : pe_t_mem[j][syst_cnt_load_dly];
+					//pe_c_in[j]	<= (ab_addr_ext == bram_addr_ext_zero) ? 32'd0 : pe_c_out_mem[j][syst_cnt_load_dly];
+				end else begin
+					pe_a[j]		<= 32'hXXXXXXXX;				
+					pe_b[j]		<= 32'hXXXXXXXX;
+					//pe_t[j]		<= 32'hXXXXXXXX;
+					//pe_c_in[j]	<= 32'hXXXXXXXX;
+				end
+		//
+		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH)
+			//
+			for (j=0; j<SYSTOLIC_ARRAY_LENGTH; j=j+1)
+				//
+				if (shreg_now_loading) begin
+					pe_a[j]		<= (qn_addr_ext > {1'b0, q_addr}) ? 32'd0 : q_data_out;
+					pe_b[j]		<= loader_dout[j];
+					//pe_t[j]		<= (q_addr == bram_addr_zero) ? 32'd0 : pe_t_mem[j][syst_cnt_load_dly];
+					//pe_c_in[j]	<= (q_addr == bram_addr_zero) ? 32'd0 : pe_c_out_mem[j][syst_cnt_load_dly];
+				end else begin
+					pe_a[j]		<= 32'hXXXXXXXX;				
+					pe_b[j]		<= 32'hXXXXXXXX;
+					//pe_t[j]		<= 32'hXXXXXXXX;
+					//pe_c_in[j]	<= 32'hXXXXXXXX;
+				end
+		//
+	
+		//
+	end
+		
+		
+		//
+		// Adder
+		//
+
+	reg				add1_ce;					// clock enable
+	wire	[31: 0]	add1_s;					// sum output
+	wire				add1_c_in;				// carry input
+	reg	[31: 0]	add1_a;					// A-input
+	reg	[31: 0]	add1_b;					// B-input
+	reg				add1_c_in_mask;		// flag to not carry anything into the very first word
+	wire				add1_c_out;				// carry output
+	
+		// add masking into carry feedback chain
+	assign add1_c_in = add1_c_out & ~add1_c_in_mask;
+
+		// mask carry for the very first word of N
+	always @(posedge clk)
+		//
+		if ((fsm_state == FSM_STATE_MULT_Q_N_CRUNCH) && shreg_done_latency_dly) 
+			add1_c_in_mask <= (ab_addr_ext == bram_addr_ext_zero) ? 1'b1 : 1'b0;
+	
+	modexpa7_adder32 add1_inst
+	(
+		.clk		(clk),
+		.ce		(add1_ce),
+		.a			(add1_a),
+		.b			(add1_b),
+		.c_in		(add1_c_in),
+		.s			(add1_s),
+		.c_out	(add1_c_out)
+	);
+	
+	always @(posedge clk)
+		//
+		add1_ce <= (fsm_next_state == FSM_STATE_MULT_Q_N_ADD_S) ? 1'b1 : 1'b0;
+		
+	always @(posedge clk)
+		//
+		if ((fsm_state == FSM_STATE_MULT_Q_N_CRUNCH) && shreg_done_latency_dly) begin
+			add1_a <= pe_p[0];
+			add1_b <= ab_data_out;
+		end
+		
+
+		//
+		// Subtractor
+		//
+		/*
+		 * This subtractor is used to calculate SN = S - N.
+		 *
+		 */
+		 
+	reg				sub1_ce;					// clock enable
+	wire	[31: 0]	sub1_d;					// difference output
+	wire				sub1_b_in;				// borrow input
+	reg	[31: 0]	sub1_a;					// A-input
+	reg	[31: 0]	sub1_b;					// B-input
+	reg				sub1_b_in_mask;		// flag to not borrow anything from the very first word
+	wire				sub1_b_out;				// borrow output
+	
+		// add masking into borrow feedback chain
+	assign sub1_b_in = sub1_b_out & ~sub1_b_in_mask;
+
+		// mask carry for the very first word of N TODO!
+	//always @(posedge clk)
+		//
+		//if ((fsm_state == FSM_STATE_MULT_Q_N_CRUNCH) && shreg_done_latency_dly) 
+			//add1_c_in_mask <= (ab_addr_ext == bram_addr_ext_zero) ? 1'b1 : 1'b0;
+	
+	modexpa7_subtractor32 sub1_inst
+	(
+		.clk		(clk),
+		.ce		(sub1_ce),
+		.a			(sub1_a),
+		.b			(sub1_b),
+		.b_in		(sub1_b_in),
+		.d			(sub1_d),
+		.b_out	(sub1_b_out)
+	);
+	
+	always @(posedge clk)
+		//
+		sub1_ce <= (fsm_next_state == FSM_STATE_MULT_Q_N_SUB_SN) && (qn_addr_ext > {1'b0, q_addr}) ? 1'b1 : 1'b0;
+		
+	always @*
+		sub1_a = add1_s;
+		
+	always @(posedge clk)
+		//
+		//if ((fsm_state == FSM_STATE_MULT_Q_N_CRUNCH) && shreg_done_latency_dly) begin
+			//add1_a <= pe_p[0];
+			//add1_b <= ab_data_out;
+		//end
+		 
+		 
+	/*
+	reg				sub1_ce;					// clock enable
+	reg	[31: 0]	sub1_d;					// difference output
+	wire				sub1_b_in;				// borrow input
+	wire	[31: 0]	sub1_a;					// A-input
+	reg	[31: 0]	sub1_b;					// B-input
+	reg				sub1_b_in_mask;		// flag to not borrow anything from the very first word*/
+//	wire	sub1_b_out;				// borrow output
+	/*
+	
+		// add masking into borrow feedback chain
+	assign sub1_b_in = sub1_b_out & ~sub1_b_in_mask;
+	
+	always @(posedge  clk)
+		//
+		if (sub1_ce)
+			//
+			{sub1_b_out, sub1_d} <= {{1{1'b0}}, sub1_a} - {{1{1'b0}}, sub1_b} - {{32{1'b0}}, sub1_b_in};
+	
+	assign sub1_a = add1_s;
+	
+	always @(posedge clk)
+		//
+		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH)
+			sub1_b <= add1_ce ? n_bram_out : 32'hXXXXXXXX;
+		else
+			sub1_b <= 32'hXXXXXXXX;
+
+	always @(posedge clk)
+		//
+		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH)
+			sub1_b_in_mask <= (add1_ce && ((qn_addr_ext - 1'b1) == {1'b0, bram_addr_last})) ? 1'b1 : 1'b0;
+		else
+			sub1_b_in_mask <= 1'b0;
+
+	always @(posedge clk)
+		//
+		if (fsm_state == FSM_STATE_MULT_Q_N_CRUNCH)
+			sub1_ce <= add1_ce && (qn_addr_ext > {1'b0, q_addr});
+		else
+			sub1_ce <= 1'b0;
+			*/
+
+
+	assign s_data_in = add1_s;
+	assign sn_data_in = sub1_d;
+	
+	always @(posedge clk) begin
+		//
+		s_wren <= ((fsm_state == FSM_STATE_MULT_Q_N_ADD_S) && (qn_addr_ext > {1'b0, q_addr})) ? 1'b1 : 1'b0;
+		sn_wren <= ((fsm_state == FSM_STATE_MULT_Q_N_SUB_SN) && (qn_addr_ext > {1'b0, q_addr})) ? 1'b1 : 1'b0;
+		//
+	end			
+		
+
+	always @(posedge clk)
+		//
+		if (fsm_state == FSM_STATE_MULT_Q_N_FINAL)
+			flag_select_s <= sub1_b_out & ~add1_c_out;
+		
+
+	always @(posedge clk)
+		//
+		case (fsm_state)
+			FSM_STATE_SAVE_START,
+			FSM_STATE_SAVE_WRITE:
+				r_data_in <= flag_select_s ? s_data_out : sn_data_out;
+		endcase
+
+		
+			
+		//
+		// FSM Process
+		//
+	always @(posedge clk or negedge rst_n)
+		//
+		if (rst_n == 1'b0)	fsm_state <= FSM_STATE_IDLE;
+		else						fsm_state <= fsm_next_state;
+	
+	
+		//
+		// FSM Transition Logic
+		//
+	always @* begin
+		//
+		fsm_next_state = FSM_STATE_STOP;
+		//
+		case (fsm_state)
+
+			FSM_STATE_IDLE:				if (ena_trig)				fsm_next_state = FSM_STATE_LOAD_B_START;
+												else							fsm_next_state = FSM_STATE_IDLE;
+			//
+			FSM_STATE_LOAD_B_START:											fsm_next_state = FSM_STATE_LOAD_B_SHIFT;
+			FSM_STATE_LOAD_B_SHIFT:		if (mult_cnt_done)			fsm_next_state = FSM_STATE_LOAD_B_WRITE;
+												else								fsm_next_state = FSM_STATE_LOAD_B_SHIFT;
+			FSM_STATE_LOAD_B_WRITE:		if (syst_cnt_init_done)		fsm_next_state = FSM_STATE_LOAD_B_FINAL;
+												else							fsm_next_state = FSM_STATE_LOAD_B_SHIFT;
+			FSM_STATE_LOAD_B_FINAL:										fsm_next_state = FSM_STATE_LOAD_N_COEFF_START;
+			//
+			FSM_STATE_LOAD_N_COEFF_START:											fsm_next_state = FSM_STATE_LOAD_N_COEFF_SHIFT;
+			FSM_STATE_LOAD_N_COEFF_SHIFT:		if (mult_cnt_done)			fsm_next_state = FSM_STATE_LOAD_N_COEFF_WRITE;
+												else								fsm_next_state = FSM_STATE_LOAD_N_COEFF_SHIFT;
+			FSM_STATE_LOAD_N_COEFF_WRITE:		if (syst_cnt_init_done)		fsm_next_state = FSM_STATE_LOAD_N_COEFF_FINAL;
+												else							fsm_next_state = FSM_STATE_LOAD_N_COEFF_SHIFT;
+			FSM_STATE_LOAD_N_COEFF_FINAL:										fsm_next_state = FSM_STATE_LOAD_N_START;
+			//
+			FSM_STATE_LOAD_N_START:											fsm_next_state = FSM_STATE_LOAD_N_SHIFT;
+			FSM_STATE_LOAD_N_SHIFT:		if (mult_cnt_done)			fsm_next_state = FSM_STATE_LOAD_N_WRITE;
+												else								fsm_next_state = FSM_STATE_LOAD_N_SHIFT;
+			FSM_STATE_LOAD_N_WRITE:		if (syst_cnt_init_done)		fsm_next_state = FSM_STATE_LOAD_N_FINAL;
+												else							fsm_next_state = FSM_STATE_LOAD_N_SHIFT;
+			FSM_STATE_LOAD_N_FINAL:										fsm_next_state = FSM_STATE_MULT_A_B_START;
+			//
+			FSM_STATE_MULT_A_B_START:									fsm_next_state = FSM_STATE_MULT_A_B_CRUNCH;
+			FSM_STATE_MULT_A_B_CRUNCH:	if (shreg_done_unload)	fsm_next_state = FSM_STATE_MULT_A_B_RELOAD;
+												else							fsm_next_state = FSM_STATE_MULT_A_B_CRUNCH;
+			FSM_STATE_MULT_A_B_RELOAD:	if (ab_addr_ext_done)	fsm_next_state = FSM_STATE_MULT_A_B_FINAL;
+												else							fsm_next_state = FSM_STATE_MULT_A_B_CRUNCH;
+			FSM_STATE_MULT_A_B_FINAL:									fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_START;
+			//
+			FSM_STATE_MULT_AB_N_COEFF_START:									fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_CRUNCH;
+			FSM_STATE_MULT_AB_N_COEFF_CRUNCH:	if (shreg_done_unload)	fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_RELOAD;
+															else							fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_CRUNCH;
+			FSM_STATE_MULT_AB_N_COEFF_RELOAD:	if (q_addr_done)	fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_FINAL;
+															else							fsm_next_state = FSM_STATE_MULT_AB_N_COEFF_CRUNCH;
+			FSM_STATE_MULT_AB_N_COEFF_FINAL:									fsm_next_state = FSM_STATE_MULT_Q_N_START;
+			//
+			FSM_STATE_MULT_Q_N_START:									fsm_next_state = FSM_STATE_MULT_Q_N_CRUNCH;
+			FSM_STATE_MULT_Q_N_CRUNCH:	if (shreg_done_unload)	fsm_next_state = FSM_STATE_MULT_Q_N_ADD_S;
+															else							fsm_next_state = FSM_STATE_MULT_Q_N_CRUNCH;
+			FSM_STATE_MULT_Q_N_ADD_S:									fsm_next_state = FSM_STATE_MULT_Q_N_SUB_SN;
+			FSM_STATE_MULT_Q_N_SUB_SN:									fsm_next_state = FSM_STATE_MULT_Q_N_RELOAD;
+			FSM_STATE_MULT_Q_N_RELOAD:	if (qn_addr_ext_done)	fsm_next_state = FSM_STATE_MULT_Q_N_FINAL;
+															else							fsm_next_state = FSM_STATE_MULT_Q_N_CRUNCH;
+			FSM_STATE_MULT_Q_N_FINAL:									fsm_next_state = FSM_STATE_SAVE_START;
+			//
+			FSM_STATE_SAVE_START:										fsm_next_state = FSM_STATE_SAVE_WRITE;
+			FSM_STATE_SAVE_WRITE:	if (r_addr_done)				fsm_next_state = FSM_STATE_SAVE_FINAL;
+											else								fsm_next_state = FSM_STATE_SAVE_WRITE;
+			FSM_STATE_SAVE_FINAL:										fsm_next_state = FSM_STATE_STOP;
+			//
+			FSM_STATE_STOP:												fsm_next_state = FSM_STATE_IDLE;
+
+		endcase
+		//
+	end
+
+
+endmodule
+
+//======================================================================
+// End of file
+//======================================================================
diff --git a/src/tb/tb_systolic_multiplier.v b/src/tb/tb_systolic_multiplier.v
index 61dc6f3..e9d532e 100644
--- a/src/tb/tb_systolic_multiplier.v
+++ b/src/tb/tb_systolic_multiplier.v
@@ -152,7 +152,7 @@ module tb_systolic_multiplier;
 	modexpa7_systolic_multiplier #

 	(

 		.OPERAND_ADDR_WIDTH		(4),	// 32 * (2**4) = 512-bit operands

-		.SYSTOLIC_ARRAY_POWER	(3)	// 2 ** 2 = 4-tap array

+		.SYSTOLIC_ARRAY_POWER	(2)	// 2 ** 2 = 4-tap array

 	)

 	uut

 	(

@@ -176,7 +176,7 @@ module tb_systolic_multiplier;
 		.r_bram_in				(core_r_data), 

 		.r_bram_wr				(core_r_wren), 

 		

-		.ab_num_words			(n_num_words)

+		.n_num_words			(n_num_words)

 	);