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////////////////////////////////////////////////////////////////////////

//

// MCS-4 common useful functions

//

// This file contains a set of useful functions used by other

// MCS-4 emulation modules.

//

// This file is part of the MCS-4 project hosted at OpenCores:

//      http://www.opencores.org/cores/mcs-4/

//

// Copyright © 2021 by Reece Pollack <rrpollack@opencores.org>

//

// These materials are provided under the Creative Commons

// "Attribution-NonCommercial-ShareAlike" (CC BY-NC-SA) Public License.

// They are NOT "public domain", and are protected by copyright.

//

// This work based on materials provided by Intel Corporation and

// others under the same license. See the file doc/License for

// details of this license.

//

////////////////////////////////////////////////////////////////////////

    //

    // Calculate integer ceil(log2(value))

    //

    // This is useful for determining the width of a register

    // required to hold the specified value.

    //

    // The implementation of $clog2() in iSim is FUBAR. This

    // performs the same function, except it actually works.

    //

    function integer clog2 (

        input integer value

    );

        integer bits;

        begin

            value = value - 1;

            for (bits = 0; value > 0; bits = bits + 1)

                value = value >> 1;

            clog2 = bits;

        end

    endfunction

    //

    // Convert Nanoseconds to Cycles

    //

    // This converts nanoseconds to cycles, rounded up. This

    // implementation assumes SYSCLK_TCY is already defined.

    //

    function integer nstocy (

        input integer ns

    );

        begin

            nstocy = (ns + (SYSCLK_TCY - 1)) / SYSCLK_TCY;

        end

    endfunction

    //

    // Calculate a Base-2 ceiling

    //

    function integer ceil2 (

        input integer value,

        input integer step

    );

        begin

            ceil2 = (value + (step - 1)) & ~(step - 1);

        end

    endfunction