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// ============================================================================

//        __

//   \\__/ o\    (C) 2018-2022  Robert Finch, Waterloo

//    \  __ /    All rights reserved.

//     \/_//     robfinch@finitron.ca

//       ||

//

//      DFPSqrt96.sv

//    - decimal floating point square root

//    - parameterized width

//    - IEEE 754 representation

//

//

// BSD 3-Clause License

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// modification, are permitted provided that the following conditions are met:

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// 1. Redistributions of source code must retain the above copyright notice, this

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// ============================================================================

import DFPPkg::*;

module DFPSqrt96(rst, clk, ce, ld, a, o, done, sqrinf, sqrneg);

parameter N=25;

input rst;

input clk;

input ce;

input ld;

input DFP96 a;

output DFP96UD o;

output done;

output sqrinf;

output sqrneg;

// registered outputs

reg sign_exe;

reg inf;

reg     overflow;

reg     underflow;

wire sign = 1'b0;

wire so;

wire [13:0] xo;

wire [(N+1)*4*2-1:0] mo;

// constants

wire [13:0] infXp = 12'hBFF;    // infinite / NaN - all ones

// The following is a template for a quiet nan. (MSB=1)

wire [N*4-1:0] qNaN  = {4'h1,{N*4-4{1'b0}}};

// variables

wire [13:0] ex1;        // sum of exponents

wire ex1c;

wire [(N+1)*4*2-1:0] sqrto;

// Operands

reg sa;                 // sign bit

reg [11:0] xa;  // exponent bits

reg [N*4-1:0] siga;

reg a_dn;                       // a/b is denormalized

reg az;

reg aInf;

reg aNan;

wire done1;

wire [7:0] lzcnt;

wire [N*4-1:0] aa;

DFP96U au;

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

// - decode the input operand

// - derive basic information

// - calculate exponent

// - calculate fraction

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

DFPUnpack96 u01 (a, au);

always @(posedge clk)

        if (ce) sa <= au.sign;

always @(posedge clk)

        if (ce) xa <= au.exp;

always @(posedge clk)

        if (ce) siga <= au.sig;

always @(posedge clk)

        if (ce) a_dn <= au.exp==12'd0;

always @(posedge clk)

        if (ce) az <= au.exp==12'd0 && au.sig==100'd0;

always @(posedge clk)

        if (ce) aInf <= au.infinity;

always @(posedge clk)

        if (ce) aNan <= au.nan;

assign ex1 = xa + 1'd1;

assign xo = ex1 >> 1'd1;

assign so = 1'b0;                               // square root of positive numbers only

assign mo = aNan ? {4'h1,aa[N*4-1:0],{N*4{1'b0}}} : sqrto;      //(sqrto << pShiftAmt);

assign sqrinf = aInf;

assign sqrneg = !az & so;

wire [(N+1)*4-1:0] siga1 = xa[0] ? {siga,4'h0} : {4'h0,siga};

wire ldd;

delay1 #(1) u3 (.clk(clk), .ce(ce), .i(ld), .o(ldd));

// Ensure an even number of digits are processed.

dfisqrt #((N+2)&-2) u2

(

        .rst(rst),

        .clk(clk),

        .ce(ce),

        .ld(ldd),

        .a({4'h0,siga1}),

        .o(sqrto),

        .done(done)

);

always @*

casez({aNan,sqrinf,sqrneg})

3'b1??:

        begin

                o.sign <= sign;

                o.nan <= 1'b1;

                o.exp <= 12'hBFF;

                o.sig <= {siga,{N*4-4{1'b0}}};

        end

3'b01?:

        begin

                o.sign <= sign;

                o.nan <= 1'b1;

                o.exp <= 12'hBFF;

                o.sig <= {4'h1,qNaN|4'h5,{N*4-4{1'b0}}};

        end

3'b001:

        begin

                o.sign <= sign;

                o.nan <= 1'b1;

                o.exp <= 12'hBFF;

                o.sig <= {4'h1,qNaN|4'h6,{N*4-4{1'b0}}};

        end

default:

        begin

                o.sign <= 1'b0;

                o.nan <= 1'b0;

                o.exp <= xo;

                o.sig <= mo;

        end

endcase

endmodule

module DFPSqrt96nr(rst, clk, ce, ld, a, o, rm, done, inf, sqrinf, sqrneg);

parameter N=25;

input rst;

input clk;

input ce;

input ld;

input  DFP96 a;

output DFP96 o;

input [2:0] rm;

output done;

output inf;

output sqrinf;

output sqrneg;

wire DFP96UD o1;

wire inf1;

wire DFP96UN fpn0;

wire done1;

wire done2;

DFPSqrt96      #(.N(N)) u1 (rst, clk, ce, ld, a, o1, done1, sqrinf, sqrneg);

DFPNormalize96 #(.N(N)) u2(.clk(clk), .ce(ce), .under_i(1'b0), .i(o1), .o(fpn0) );

DFPRound96     #(.N(N)) u3(.clk(clk), .ce(ce), .rm(rm), .i(fpn0), .o(o) );

delay2      #(1)   u5(.clk(clk), .ce(ce), .i(inf1), .o(inf));

delay2          #(1)   u8(.clk(clk), .ce(ce), .i(done1), .o(done2));

assign done = done1&done2;

endmodule