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[/] [xulalx25soc/] [trunk/] [rtl/] [cpu/] [div.v] - Rev 118
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/////////////////////////////////////////////////////////////////////////////// // // Filename: div.v // // Project: Zip CPU -- a small, lightweight, RISC CPU soft core // // Purpose: Provide an Integer divide capability to the Zip CPU. // // // Creator: Dan Gisselquist, Ph.D. // Gisselquist Technology, LLC // /////////////////////////////////////////////////////////////////////////////// // // Copyright (C) 2015-2016, Gisselquist Technology, LLC // // This program is free software (firmware): you can redistribute it and/or // modify it under the terms of the GNU General Public License as published // by the Free Software Foundation, either version 3 of the License, or (at // your option) any later version. // // This program is distributed in the hope that it will be useful, but WITHOUT // ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or // FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License // for more details. // // License: GPL, v3, as defined and found on www.gnu.org, // http://www.gnu.org/licenses/gpl.html // // /////////////////////////////////////////////////////////////////////////////// // // `include "cpudefs.v" // module div(i_clk, i_rst, i_wr, i_signed, i_numerator, i_denominator, o_busy, o_valid, o_err, o_quotient, o_flags); parameter BW=32, LGBW = 5; input i_clk, i_rst; // Input parameters input i_wr, i_signed; input [(BW-1):0] i_numerator, i_denominator; // Output parameters output reg o_busy, o_valid, o_err; output reg [(BW-1):0] o_quotient; output wire [3:0] o_flags; // r_busy is an internal busy register. It will clear one clock // before we are valid, so it can't be o_busy ... // reg r_busy; reg [(2*BW-2):0] r_divisor; reg [(BW-1):0] r_dividend; wire [(BW):0] diff; // , xdiff[(BW-1):0]; assign diff = r_dividend - r_divisor[(BW-1):0]; // assign xdiff= r_dividend - { 1'b0, r_divisor[(BW-1):1] }; reg r_sign, pre_sign, r_z, r_c, last_bit; reg [(LGBW-1):0] r_bit; reg zero_divisor; initial zero_divisor = 1'b0; always @(posedge i_clk) zero_divisor <= (r_divisor == 0)&&(r_busy); initial r_busy = 1'b0; always @(posedge i_clk) if (i_rst) r_busy <= 1'b0; else if (i_wr) r_busy <= 1'b1; else if ((last_bit)||(zero_divisor)) r_busy <= 1'b0; initial o_busy = 1'b0; always @(posedge i_clk) if (i_rst) o_busy <= 1'b0; else if (i_wr) o_busy <= 1'b1; else if (((last_bit)&&(~r_sign))||(zero_divisor)) o_busy <= 1'b0; else if (~r_busy) o_busy <= 1'b0; always @(posedge i_clk) if ((i_rst)||(i_wr)) o_valid <= 1'b0; else if (r_busy) begin if ((last_bit)||(zero_divisor)) o_valid <= (zero_divisor)||(~r_sign); end else if (r_sign) begin o_valid <= (~zero_divisor); // 1'b1; end else o_valid <= 1'b0; initial o_err = 1'b0; always @(posedge i_clk) if((i_rst)||(o_valid)) o_err <= 1'b0; else if (((r_busy)||(r_sign))&&(zero_divisor)) o_err <= 1'b1; else o_err <= 1'b0; initial last_bit = 1'b0; always @(posedge i_clk) if ((i_wr)||(pre_sign)||(i_rst)) last_bit <= 1'b0; else if (r_busy) last_bit <= (r_bit == {{(LGBW-1){1'b0}},1'b1}); always @(posedge i_clk) // if (i_rst) r_busy <= 1'b0; // else if (i_wr) begin // // Set our values upon an initial command. Here's // where we come in and start. // // r_busy <= 1'b1; // o_quotient <= 0; r_bit <= {(LGBW){1'b1}}; r_divisor <= { i_denominator, {(BW-1){1'b0}} }; r_dividend <= i_numerator; r_sign <= 1'b0; pre_sign <= i_signed; r_z <= 1'b1; end else if (pre_sign) begin // // Note that we only come in here, for one clock, if // our initial value may have been signed. If we are // doing an unsigned divide, we then skip this step. // r_sign <= ((r_divisor[(2*BW-2)])^(r_dividend[(BW-1)])); // Negate our dividend if necessary so that it becomes // a magnitude only value if (r_dividend[BW-1]) r_dividend <= -r_dividend; // Do the same with the divisor--rendering it into // a magnitude only. if (r_divisor[(2*BW-2)]) r_divisor[(2*BW-2):(BW-1)] <= -r_divisor[(2*BW-2):(BW-1)]; // // We only do this stage for a single clock, so go on // with the rest of the divide otherwise. pre_sign <= 1'b0; end else if (r_busy) begin // While the divide is taking place, we examine each bit // in turn here. // r_bit <= r_bit + {(LGBW){1'b1}}; // r_bit = r_bit - 1; r_divisor <= { 1'b0, r_divisor[(2*BW-2):1] }; if (|r_divisor[(2*BW-2):(BW)]) begin end else if (diff[BW]) begin // // diff = r_dividend - r_divisor[(BW-1):0]; // // If this value was negative, there wasn't // enough value in the dividend to support // pulling off a bit. We'll move down a bit // therefore and try again. // end else begin // // Put a '1' into our output accumulator. // Subtract the divisor from the dividend, // and then move on to the next bit // r_dividend <= diff[(BW-1):0]; o_quotient[r_bit[(LGBW-1):0]] <= 1'b1; r_z <= 1'b0; end r_sign <= (r_sign)&&(~zero_divisor); end else if (r_sign) begin r_sign <= 1'b0; o_quotient <= -o_quotient; end // Set Carry on an exact divide wire w_n; always @(posedge i_clk) r_c <= (r_busy)&&((diff == 0)||(r_dividend == 0)); assign w_n = o_quotient[(BW-1)]; assign o_flags = { 1'b0, w_n, r_c, r_z }; endmodule