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[/] [amber/] [trunk/] [hw/] [vlog/] [amber25/] [a25_multiply.v] - Rev 36
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////////////////////////////////////////////////////////////////// // // // Multiplication Module for Amber 25 Core // // // // This file is part of the Amber project // // http://www.opencores.org/project,amber // // // // Description // // 64-bit Booth signed or unsigned multiply and // // multiply-accumulate supported. It takes about 38 clock // // cycles to complete an operation. // // // // Author(s): // // - Conor Santifort, csantifort.amber@gmail.com // // // ////////////////////////////////////////////////////////////////// // // // Copyright (C) 2011 Authors and OPENCORES.ORG // // // // This source file may be used and distributed without // // restriction provided that this copyright statement is not // // removed from the file and that any derivative work contains // // the original copyright notice and the associated disclaimer. // // // // This source file is free software; you can redistribute it // // and/or modify it under the terms of the GNU Lesser General // // Public License as published by the Free Software Foundation; // // either version 2.1 of the License, or (at your option) any // // later version. // // // // This source is distributed in the hope that it will be // // useful, but WITHOUT ANY WARRANTY; without even the implied // // warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR // // PURPOSE. See the GNU Lesser General Public License for more // // details. // // // // You should have received a copy of the GNU Lesser General // // Public License along with this source; if not, download it // // from http://www.opencores.org/lgpl.shtml // // // ////////////////////////////////////////////////////////////////// // bit 0 go, bit 1 accumulate // Command: // 4'b01 : MUL - 32 bit multiplication // 4'b11 : MLA - 32 bit multiply and accumulate // // 34-bit Booth adder // The adder needs to be 34 bit to deal with signed and unsigned 32-bit // multiplication inputs. This adds 1 extra bit. Then to deal with the // case of two max negative numbers another bit is required. // module a25_multiply ( input i_clk, input i_core_stall, input [31:0] i_a_in, // Rds input [31:0] i_b_in, // Rm input [1:0] i_function, input i_execute, output [31:0] o_out, output [1:0] o_flags, // [1] = N, [0] = Z output reg o_done = 'd0 // goes high 2 cycles before completion ); wire enable; wire accumulate; wire [33:0] multiplier; wire [33:0] multiplier_bar; wire [33:0] sum; wire [33:0] sum34_b; reg [5:0] count = 'd0; reg [5:0] count_nxt; reg [67:0] product = 'd0; reg [67:0] product_nxt; reg [1:0] flags_nxt; reg sum_acc1_carry = 'd0; reg sum_acc1_carry_nxt; wire [32:0] sum_acc1; // the MSB is the carry out for the upper 32 bit addition assign enable = i_function[0]; assign accumulate = i_function[1]; assign multiplier = { 2'd0, i_a_in} ; assign multiplier_bar = ~{ 2'd0, i_a_in} + 34'd1 ; assign sum34_b = product[1:0] == 2'b01 ? multiplier : product[1:0] == 2'b10 ? multiplier_bar : 34'd0 ; // Use DSP modules from Xilinx Spartan6 FPGA devices `ifdef XILINX_FPGA // ----------------------------------- // 34-bit adder - booth multiplication // ----------------------------------- `ifdef XILINX_SPARTAN6_FPGA xs6_addsub_n #(.WIDTH(34)) `endif `ifdef XILINX_VIRTEX6_FPGA xv6_addsub_n #(.WIDTH(34)) `endif u_xx_addsub_34_sum ( .i_a ( product[67:34] ), .i_b ( sum34_b ), .i_cin ( 1'd0 ), .i_sub ( 1'd0 ), .o_sum ( sum ), .o_co ( ) ); // ------------------------------------ // 33-bit adder - accumulate operations // ------------------------------------ `ifdef XILINX_SPARTAN6_FPGA xs6_addsub_n #(.WIDTH(33)) `endif `ifdef XILINX_VIRTEX6_FPGA xv6_addsub_n #(.WIDTH(33)) `endif u_xx_addsub_33_acc1 ( .i_a ( {1'd0, product[32:1]} ), .i_b ( {1'd0, i_a_in} ), .i_cin ( 1'd0 ), .i_sub ( 1'd0 ), .o_sum ( sum_acc1 ), .o_co ( ) ); `else // ----------------------------------- // 34-bit adder - booth multiplication // ----------------------------------- assign sum = product[67:34] + sum34_b; // ------------------------------------ // 33-bit adder - accumulate operations // ------------------------------------ assign sum_acc1 = {1'd0, product[32:1]} + {1'd0, i_a_in}; `endif always @* begin // Defaults count_nxt = count; sum_acc1_carry_nxt = sum_acc1_carry; product_nxt = product; // update Negative and Zero flags // Use registered value of product so this adds an extra cycle // but this avoids having the 64-bit zero comparator on the // main adder path flags_nxt = { product[32], product[32:1] == 32'd0 }; if ( count == 6'd0 ) product_nxt = {33'd0, 1'd0, i_b_in, 1'd0 } ; else if ( count <= 6'd33 ) product_nxt = { sum[33], sum, product[33:1]} ; else if ( count == 6'd34 && accumulate ) begin // Note that bit 0 is not part of the product. It is used during the booth // multiplication algorithm product_nxt = { product[64:33], sum_acc1[31:0], 1'd0}; // Accumulate sum_acc1_carry_nxt = sum_acc1[32]; end // Multiplication state counter if (count == 6'd0) // start count_nxt = enable ? 6'd1 : 6'd0; else if ((count == 6'd34 && !accumulate) || // MUL (count == 6'd35 && accumulate) ) // MLA count_nxt = 6'd0; else count_nxt = count + 1'd1; end always @ ( posedge i_clk ) if ( !i_core_stall ) begin count <= i_execute ? count_nxt : count; product <= i_execute ? product_nxt : product; sum_acc1_carry <= i_execute ? sum_acc1_carry_nxt : sum_acc1_carry; o_done <= i_execute ? count == 6'd31 : o_done; end // Outputs assign o_out = product[32:1]; assign o_flags = flags_nxt; endmodule
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