diff options
Diffstat (limited to 'rtl/modular/modular_subtractor.v')
-rw-r--r-- | rtl/modular/modular_subtractor.v | 510 |
1 files changed, 255 insertions, 255 deletions
diff --git a/rtl/modular/modular_subtractor.v b/rtl/modular/modular_subtractor.v index 322aec4..1637f45 100644 --- a/rtl/modular/modular_subtractor.v +++ b/rtl/modular/modular_subtractor.v @@ -2,7 +2,7 @@ // // modular_subtractor.v // ----------------------------------------------------------------------------- -// Modular subtractor.
+// Modular subtractor. // // Authors: Pavel Shatov // @@ -34,259 +34,259 @@ // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE // POSSIBILITY OF SUCH DAMAGE. // -//------------------------------------------------------------------------------
-
-module modular_subtractor
- (
- clk, rst_n,
- ena, rdy,
- ab_addr, n_addr, d_addr, d_wren, - a_din, b_din, n_din, d_dout
- );
-
-
- //
- // Parameters
- //
- parameter OPERAND_NUM_WORDS = 8;
- parameter WORD_COUNTER_WIDTH = 3;
-
-
- // - // Handy Numbers - // - localparam [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_ZERO = 0; - localparam [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_LAST = OPERAND_NUM_WORDS - 1;
-
-
- // - // Handy Functions - // - function [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_NEXT_OR_ZERO; - input [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_CURRENT; - begin - WORD_INDEX_NEXT_OR_ZERO = (WORD_INDEX_CURRENT < WORD_INDEX_LAST) ? - WORD_INDEX_CURRENT + 1'b1 : WORD_INDEX_ZERO; - end - endfunction
-
-
- // - // Ports - // - input wire clk; // system clock - input wire rst_n; // active-low async reset - - input wire ena; // enable input - output wire rdy; // ready output -
- output wire [WORD_COUNTER_WIDTH-1:0] ab_addr; // index of current A and B words
- output wire [WORD_COUNTER_WIDTH-1:0] n_addr; // index of current N word
- output wire [WORD_COUNTER_WIDTH-1:0] d_addr; // index of current D word
- output wire d_wren; // store current D word now
- - input wire [ 31:0] a_din; // A - input wire [ 31:0] b_din; // B - input wire [ 31:0] n_din; // N - output wire [ 31:0] d_dout; // D = (A - B) mod N
-
-
- //
- // Word Indices
- //
- reg [WORD_COUNTER_WIDTH-1:0] index_ab;
- reg [WORD_COUNTER_WIDTH-1:0] index_n;
- reg [WORD_COUNTER_WIDTH-1:0] index_d;
-
- /* map registers to output ports */
- assign ab_addr = index_ab;
- assign n_addr = index_n;
- assign d_addr = index_d;
-
-
- //
- // Subtractor
- //
- wire [31: 0] sub32_d;
- wire sub32_b_in;
- wire sub32_b_out;
-
- subtractor32_wrapper subtractor32
- ( - .clk (clk), - .a (a_din), - .b (b_din), - .d (sub32_d), - .b_in (sub32_b_in), - .b_out (sub32_b_out) - );
-
-
- //
- // Adder
- //
- wire [31: 0] add32_s;
- wire add32_c_in;
- wire add32_c_out;
-
- adder32_wrapper adder32
- ( - .clk (clk), - .a (sub32_d), - .b (n_din), - .s (add32_s), - .c_in (add32_c_in), - .c_out (add32_c_out) - );
-
-
- //
- // FSM
- //
-
- localparam FSM_SHREG_WIDTH = 2*OPERAND_NUM_WORDS + 5;
-
- reg [FSM_SHREG_WIDTH-1:0] fsm_shreg;
-
- assign rdy = fsm_shreg[0];
-
- wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_inc_index_ab = fsm_shreg[FSM_SHREG_WIDTH - (0 * OPERAND_NUM_WORDS + 1) : FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 0)];
- wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_inc_index_n = fsm_shreg[FSM_SHREG_WIDTH - (0 * OPERAND_NUM_WORDS + 2) : FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 1)];
- wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_store_dif_ab = fsm_shreg[FSM_SHREG_WIDTH - (0 * OPERAND_NUM_WORDS + 3) : FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 2)];
- wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_store_dif_ab_n = fsm_shreg[FSM_SHREG_WIDTH - (0 * OPERAND_NUM_WORDS + 4) : FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 3)];
- wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_store_data_d = fsm_shreg[FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 4) : FSM_SHREG_WIDTH - (2 * OPERAND_NUM_WORDS + 3)];
- wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_inc_index_d = fsm_shreg[FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 5) : FSM_SHREG_WIDTH - (2 * OPERAND_NUM_WORDS + 4)];
-
- wire fsm_latch_msb_borrow = fsm_shreg[FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 2)];
-
- wire inc_index_ab = |fsm_shreg_inc_index_ab;
- wire inc_index_n = |fsm_shreg_inc_index_n;
- wire store_dif_ab = |fsm_shreg_store_dif_ab;
- wire store_dif_ab_n = |fsm_shreg_store_dif_ab_n;
- wire store_data_d = |fsm_shreg_store_data_d;
- wire inc_index_d = |fsm_shreg_inc_index_d;
-
- always @(posedge clk or negedge rst_n) - // - if (rst_n == 1'b0)
- //
- fsm_shreg <= {{FSM_SHREG_WIDTH-1{1'b0}}, 1'b1};
- //
- else begin
- //
- if (rdy) fsm_shreg <= {ena, {FSM_SHREG_WIDTH-2{1'b0}}, ~ena};
- //
- else fsm_shreg <= {1'b0, fsm_shreg[FSM_SHREG_WIDTH-1:1]};
- //
- end
-
-
- //
- // Borrow & Carry Masking Logic
- //
- reg sub32_b_mask;
- reg add32_c_mask;
-
-
- always @(posedge clk) begin
- //
- sub32_b_mask <= (index_ab == WORD_INDEX_ZERO) ? 1'b1 : 1'b0;
- add32_c_mask <= (index_n == WORD_INDEX_ZERO) ? 1'b1 : 1'b0;
- //
- end
-
- assign sub32_b_in = sub32_b_out & ~sub32_b_mask;
- assign add32_c_in = add32_c_out & ~add32_c_mask;
-
-
-
- //
- // Borrow & Carry Latch Logic
- //
- reg sub32_borrow_latch;
-
- always @(posedge clk) begin
- //
- if (fsm_latch_msb_borrow) sub32_borrow_latch <= sub32_b_out;
- //
- end
-
-
- //
- // Intermediate Results
- //
- reg [32*OPERAND_NUM_WORDS-1:0] d_ab;
- reg [32*OPERAND_NUM_WORDS-1:0] d_ab_n;
-
- always @(posedge clk)
- //
- if (store_data_d) begin
- //
- d_ab <= {{32{1'bX}}, d_ab[32*OPERAND_NUM_WORDS-1:32]};
- d_ab_n <= {{32{1'bX}}, d_ab_n[32*OPERAND_NUM_WORDS-1:32]};
- //
- end else begin
- //
- if (store_dif_ab) d_ab <= {sub32_d, d_ab[32*OPERAND_NUM_WORDS-1:32]};
- if (store_dif_ab_n) d_ab_n <= {add32_s, d_ab_n[32*OPERAND_NUM_WORDS-1:32]};
- //
- end
-
-
- // - // Word Index Increment Logic - //
- always @(posedge clk) - //
- if (rdy) begin
- //
- index_ab <= WORD_INDEX_ZERO;
- index_n <= WORD_INDEX_ZERO;
- index_d <= WORD_INDEX_ZERO;
- //
- end else begin
- //
- if (inc_index_ab) index_ab <= WORD_INDEX_NEXT_OR_ZERO(index_ab);
- if (inc_index_n) index_n <= WORD_INDEX_NEXT_OR_ZERO(index_n);
- if (inc_index_d) index_d <= WORD_INDEX_NEXT_OR_ZERO(index_d);
- //
- end
-
-
- //
- // Output Sum Selector
- //
- wire mux_select_ab_n = sub32_borrow_latch;
-
-
- //
- // Output Data and Write Enable Logic
- //
- reg d_wren_reg;
- reg [31: 0] d_dout_reg;
- wire [31: 0] d_dout_mux = mux_select_ab_n ? d_ab_n[31:0] : d_ab[31:0];
-
- assign d_wren = d_wren_reg;
- assign d_dout = d_dout_reg;
-
- always @(posedge clk) - //
- if (rdy) begin
- //
- d_wren_reg <= 1'b0;
- d_dout_reg <= {32{1'bX}};
- //
- end else begin
- //
- d_wren_reg <= store_data_d;
- d_dout_reg <= store_data_d ? d_dout_mux : {32{1'bX}};
- //
- end
-
-
-endmodule
-
-
+//------------------------------------------------------------------------------ + +module modular_subtractor + ( + clk, rst_n, + ena, rdy, + ab_addr, n_addr, d_addr, d_wren, + a_din, b_din, n_din, d_dout + ); + + + // + // Parameters + // + parameter OPERAND_NUM_WORDS = 8; + parameter WORD_COUNTER_WIDTH = 3; + + + // + // Handy Numbers + // + localparam [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_ZERO = 0; + localparam [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_LAST = OPERAND_NUM_WORDS - 1; + + + // + // Handy Functions + // + function [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_NEXT_OR_ZERO; + input [WORD_COUNTER_WIDTH-1:0] WORD_INDEX_CURRENT; + begin + WORD_INDEX_NEXT_OR_ZERO = (WORD_INDEX_CURRENT < WORD_INDEX_LAST) ? + WORD_INDEX_CURRENT + 1'b1 : WORD_INDEX_ZERO; + end + endfunction + + + // + // Ports + // + input wire clk; // system clock + input wire rst_n; // active-low async reset + + input wire ena; // enable input + output wire rdy; // ready output + + output wire [WORD_COUNTER_WIDTH-1:0] ab_addr; // index of current A and B words + output wire [WORD_COUNTER_WIDTH-1:0] n_addr; // index of current N word + output wire [WORD_COUNTER_WIDTH-1:0] d_addr; // index of current D word + output wire d_wren; // store current D word now + + input wire [ 31:0] a_din; // A + input wire [ 31:0] b_din; // B + input wire [ 31:0] n_din; // N + output wire [ 31:0] d_dout; // D = (A - B) mod N + + + // + // Word Indices + // + reg [WORD_COUNTER_WIDTH-1:0] index_ab; + reg [WORD_COUNTER_WIDTH-1:0] index_n; + reg [WORD_COUNTER_WIDTH-1:0] index_d; + + /* map registers to output ports */ + assign ab_addr = index_ab; + assign n_addr = index_n; + assign d_addr = index_d; + + + // + // Subtractor + // + wire [31: 0] sub32_d; + wire sub32_b_in; + wire sub32_b_out; + + subtractor32_wrapper subtractor32 + ( + .clk (clk), + .a (a_din), + .b (b_din), + .d (sub32_d), + .b_in (sub32_b_in), + .b_out (sub32_b_out) + ); + + + // + // Adder + // + wire [31: 0] add32_s; + wire add32_c_in; + wire add32_c_out; + + adder32_wrapper adder32 + ( + .clk (clk), + .a (sub32_d), + .b (n_din), + .s (add32_s), + .c_in (add32_c_in), + .c_out (add32_c_out) + ); + + + // + // FSM + // + + localparam FSM_SHREG_WIDTH = 2*OPERAND_NUM_WORDS + 5; + + reg [FSM_SHREG_WIDTH-1:0] fsm_shreg; + + assign rdy = fsm_shreg[0]; + + wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_inc_index_ab = fsm_shreg[FSM_SHREG_WIDTH - (0 * OPERAND_NUM_WORDS + 1) : FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 0)]; + wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_inc_index_n = fsm_shreg[FSM_SHREG_WIDTH - (0 * OPERAND_NUM_WORDS + 2) : FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 1)]; + wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_store_dif_ab = fsm_shreg[FSM_SHREG_WIDTH - (0 * OPERAND_NUM_WORDS + 3) : FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 2)]; + wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_store_dif_ab_n = fsm_shreg[FSM_SHREG_WIDTH - (0 * OPERAND_NUM_WORDS + 4) : FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 3)]; + wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_store_data_d = fsm_shreg[FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 4) : FSM_SHREG_WIDTH - (2 * OPERAND_NUM_WORDS + 3)]; + wire [OPERAND_NUM_WORDS-1:0] fsm_shreg_inc_index_d = fsm_shreg[FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 5) : FSM_SHREG_WIDTH - (2 * OPERAND_NUM_WORDS + 4)]; + + wire fsm_latch_msb_borrow = fsm_shreg[FSM_SHREG_WIDTH - (1 * OPERAND_NUM_WORDS + 2)]; + + wire inc_index_ab = |fsm_shreg_inc_index_ab; + wire inc_index_n = |fsm_shreg_inc_index_n; + wire store_dif_ab = |fsm_shreg_store_dif_ab; + wire store_dif_ab_n = |fsm_shreg_store_dif_ab_n; + wire store_data_d = |fsm_shreg_store_data_d; + wire inc_index_d = |fsm_shreg_inc_index_d; + + always @(posedge clk or negedge rst_n) + // + if (rst_n == 1'b0) + // + fsm_shreg <= {{FSM_SHREG_WIDTH-1{1'b0}}, 1'b1}; + // + else begin + // + if (rdy) fsm_shreg <= {ena, {FSM_SHREG_WIDTH-2{1'b0}}, ~ena}; + // + else fsm_shreg <= {1'b0, fsm_shreg[FSM_SHREG_WIDTH-1:1]}; + // + end + + + // + // Borrow & Carry Masking Logic + // + reg sub32_b_mask; + reg add32_c_mask; + + + always @(posedge clk) begin + // + sub32_b_mask <= (index_ab == WORD_INDEX_ZERO) ? 1'b1 : 1'b0; + add32_c_mask <= (index_n == WORD_INDEX_ZERO) ? 1'b1 : 1'b0; + // + end + + assign sub32_b_in = sub32_b_out & ~sub32_b_mask; + assign add32_c_in = add32_c_out & ~add32_c_mask; + + + + // + // Borrow & Carry Latch Logic + // + reg sub32_borrow_latch; + + always @(posedge clk) begin + // + if (fsm_latch_msb_borrow) sub32_borrow_latch <= sub32_b_out; + // + end + + + // + // Intermediate Results + // + reg [32*OPERAND_NUM_WORDS-1:0] d_ab; + reg [32*OPERAND_NUM_WORDS-1:0] d_ab_n; + + always @(posedge clk) + // + if (store_data_d) begin + // + d_ab <= {{32{1'bX}}, d_ab[32*OPERAND_NUM_WORDS-1:32]}; + d_ab_n <= {{32{1'bX}}, d_ab_n[32*OPERAND_NUM_WORDS-1:32]}; + // + end else begin + // + if (store_dif_ab) d_ab <= {sub32_d, d_ab[32*OPERAND_NUM_WORDS-1:32]}; + if (store_dif_ab_n) d_ab_n <= {add32_s, d_ab_n[32*OPERAND_NUM_WORDS-1:32]}; + // + end + + + // + // Word Index Increment Logic + // + always @(posedge clk) + // + if (rdy) begin + // + index_ab <= WORD_INDEX_ZERO; + index_n <= WORD_INDEX_ZERO; + index_d <= WORD_INDEX_ZERO; + // + end else begin + // + if (inc_index_ab) index_ab <= WORD_INDEX_NEXT_OR_ZERO(index_ab); + if (inc_index_n) index_n <= WORD_INDEX_NEXT_OR_ZERO(index_n); + if (inc_index_d) index_d <= WORD_INDEX_NEXT_OR_ZERO(index_d); + // + end + + + // + // Output Sum Selector + // + wire mux_select_ab_n = sub32_borrow_latch; + + + // + // Output Data and Write Enable Logic + // + reg d_wren_reg; + reg [31: 0] d_dout_reg; + wire [31: 0] d_dout_mux = mux_select_ab_n ? d_ab_n[31:0] : d_ab[31:0]; + + assign d_wren = d_wren_reg; + assign d_dout = d_dout_reg; + + always @(posedge clk) + // + if (rdy) begin + // + d_wren_reg <= 1'b0; + d_dout_reg <= {32{1'bX}}; + // + end else begin + // + d_wren_reg <= store_data_d; + d_dout_reg <= store_data_d ? d_dout_mux : {32{1'bX}}; + // + end + + +endmodule + + //------------------------------------------------------------------------------ // End-of-File -//------------------------------------------------------------------------------
+//------------------------------------------------------------------------------ |