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

//        __

//   \\__/ o\    (C) 2013,2015  Robert Finch, Stratford

//    \  __ /    All rights reserved.

//     \/_//     robfinch<remove>@finitron.ca

//       ||

//

// 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 3 of the License, or     

// (at your option) any later version.                                      

//                                                                          

// This source file 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 General Public License for more details.                             

//                                                                          

// You should have received a copy of the GNU General Public License        

// along with this program.  If not, see <http://www.gnu.org/licenses/>.    

//

//

// Thor Superscaler

// Thor_divider.v

//  - 64 bit divider

//

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

//

module Thor_divider(rst, clk, ld, abort, sgn, isDivi, a, b, imm, qo, ro, dvByZr, done, idle);

parameter WID=64;

parameter DIV=3'd3;

parameter IDLE=3'd4;

parameter DONE=3'd5;

input clk;

input rst;

input ld;

input abort;

input sgn;

input isDivi;

input [WID-1:0] a;

input [WID-1:0] b;

input [WID-1:0] imm;

output [WID-1:0] qo;

reg [WID-1:0] qo;

output [WID-1:0] ro;

reg [WID-1:0] ro;

output done;

output idle;

output dvByZr;

reg dvByZr;

reg [WID-1:0] aa,bb;

reg so;

reg [2:0] state;

reg [7:0] cnt;

wire cnt_done = cnt==8'd0;

assign done = state==DONE||(state==IDLE && !ld);

assign idle = state==IDLE;

reg ce1;

reg [WID-1:0] q;

reg [WID:0] r;

wire b0 = bb <= r;

wire [WID-1:0] r1 = b0 ? r - bb : r;

initial begin

    q = 64'd0;

    r = 64'd0;

    qo = 64'd0;

    ro = 64'd0;

end

always @(posedge clk)

if (rst) begin

        aa <= {WID{1'b0}};

        bb <= {WID{1'b0}};

        q <= {WID{1'b0}};

        r <= {WID{1'b0}};

        qo <= {WID{1'b0}};

        ro <= {WID{1'b0}};

        cnt <= 8'd0;

        dvByZr <= 1'b0;

        state <= IDLE;

end

else

begin

if (abort)

    cnt <= 8'd00;

else if (!cnt_done)

        cnt <= cnt - 8'd1;

case(state)

IDLE:

        if (ld) begin

                if (sgn) begin

                        q <= a[WID-1] ? -a : a;

                        bb <= isDivi ? (imm[WID-1] ? -imm : imm) :(b[WID-1] ? -b : b);

                        so <= isDivi ? a[WID-1] ^ imm[WID-1] : a[WID-1] ^ b[WID-1];

                end

                else begin

                        q <= a;

                        bb <= isDivi ? imm : b;

                        so <= 1'b0;

                        $display("bb=%d", isDivi ? imm : b);

                end

                dvByZr <= isDivi ? imm=={WID{1'b0}} : b=={WID{1'b0}};

                r <= {WID{1'b0}};

                cnt <= WID+1;

                state <= DIV;

        end

DIV:

        if (!cnt_done) begin

                $display("cnt:%d r1=%h q[63:0]=%h", cnt,r1,q);

                q <= {q[WID-2:0],b0};

                r <= {r1,q[WID-1]};

        end

        else begin

                $display("cnt:%d r1=%h q[63:0]=%h", cnt,r1,q);

                if (sgn) begin

                        if (so) begin

                                qo <= -q;

                                ro <= -r[WID:1];

                        end

                        else begin

                                qo <= q;

                                ro <= r[WID:1];

                        end

                end

                else begin

                        qo <= q;

                        ro <= r[WID:1];

                end

                state <= DONE;

        end

DONE:

        state <= IDLE;

endcase

end

endmodule

module Thor_divider_tb();

parameter WID=64;

reg rst;

reg clk;

reg ld;

wire done;

wire [WID-1:0] qo,ro;

initial begin

        clk = 1;

        rst = 0;

        #100 rst = 1;

        #100 rst = 0;

        #100 ld = 1;

        #150 ld = 0;

end

always #10 clk = ~clk;  //  50 MHz

Thor_divider #(WID) u1

(

        .rst(rst),

        .clk(clk),

        .ld(ld),

        .sgn(1'b1),

        .isDivi(1'b0),

        .a(64'd10005),

        .b(64'd27),

        .imm(64'd123),

        .qo(qo),

        .ro(ro),

        .dvByZr(),

        .done(done)

);

endmodule