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// ============================================================================
//        __
//   \\__/ o\    (C) 2022  Robert Finch, Waterloo
//    \  __ /    All rights reserved.
//     \/_//     robfinch<remove>@finitron.ca
//       ||
//
//      df128Toi.sv
//  - convert decimal floating point to integer
//
// BSD 3-Clause License
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
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//
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//                                                                          
// ============================================================================

import DFPPkg::*;

module df96Toi (rst, clk, ce, ld, op, i, o, overflow, done);
input rst;
input clk;
input ce;
input ld;
input op;                                               // 1 = signed, 0 = unsigned
input [95:0] i;         // float input
output [95:0] o;                // integer output
output overflow;
output done;

wire done1;
reg done2;
assign done = done1 & done2;

wire [95:0] sig;

DFP96U ui;
DFPUnpack96 uunpk1 (i, ui);

wire [95:0] maxInt = op ? {1'd0,{95{1'b1}}} : {96{1'b1}};               // maximum integer value
wire [11:0] zeroXp = 12'h5FF;

reg sgn;                                                                        // sign
always_ff @(posedge clk)
        if (ce) sgn = ui.sign;
wire [11:0] exp = ui.exp;               // exponent

wire iz = i[94:0]==0;                   // zero value (special)

wire [12:0] ovx = exp - zeroXp;
assign overflow  = ovx > 23 && !ovx[12];        // lots of numbers are too big - don't forget one less bit is available due to signed values
wire underflow = exp < zeroXp - 2'd1;                   // value less than 1/2

wire [7:0] shamt = 8'd128 - {(exp - zeroXp),2'd0};      // exp - zeroXp will be <= MSB

wire [128:0] o1 = {ui.sig,33'b0} >> shamt;      // keep an extra bit for rounding
wire [95:0] o2;         // round up
reg [95:0] o3;

DDBCDToBin #(.WID(96)) ub2b1
(
        .rst(rst),
        .clk(clk),
        .ld(ld),
        .bcd({o1[128:1]+o1[0]}),
        .bin(o2),
        .done(done1)
);


always @(posedge clk)
        if (ce) begin
                if (underflow|iz)
                        o3 <='d0;
                else if (overflow)
                        o3 <= maxInt;
                // value between 1/2 and 1 - round up
                else if (exp==zeroXp-1)
                        o3 <= 96'd1;
                // value > 1
                else
                        o3 <= o2;
        end
always @(posedge clk)
        if (ce) done2 <= done1;
                
assign o = (op & sgn) ? -o3 : o3;                                       // adjust output for correct signed value

endmodule