Fwd: Re: [sv-bc] Re: implicit instantiation of top-level modules?

From: Stefen Boyd (stefen@boyd.com)
Date: Thu Jul 10 2003 - 22:51:48 PDT

  • Next message: Steven Sharp: "Re: [sv-bc] Re: implicit instantiation of top-level modules?"

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    >Date: Thu, 10 Jul 2003 10:43:14 -0700
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    >: Non-member submission from [Greg Jaxon <Greg.Jaxon@synopsys.com>]
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    >Date: Thu, 10 Jul 2003 10:42:43 -0700
    >From: Greg Jaxon <Greg.Jaxon@synopsys.com>
    >Organization: //Synopsys/ICBU/HDL Compiler
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    >Cc: Shalom Bresticker <Shalom.Bresticker@motorola.com>,
    > Dave Rich <David.Rich@synopsys.com>, sv-bc@eda.org, etf@boyd.com
    >Subject: Re: [sv-bc] Re: implicit instantiation of top-level modules?
    >References:
    ><200307072349.h67NnaZJ009789@server.eda.org>
    ><5.1.0.14.2.20030708085821.00a8b9f0@pophost.synopsys.com>
    ><3F0B75CF.1020101@synopsys.com>
    ><3F0BBD68.77AE7AE5@motorola.com>
    ><16140.15471.133845.747601@gargle.gargle.HOWL>
    ><3F0C5274.9010809@synopsys.com> <3F0D2B87.13B5E355@motorola.com>
    ><16141.40510.337835.72428@gargle.gargle.HOWL>
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    >
    >Michael McNamara wrote:
    >
    > > [T]his allows is an additional fairly powerfull
    > > capability: Easy reference to a sibling.
    > >
    > > Let us say you have a module, implementing a Flip Flop:
    > >
    > > module ff (input D, CLK, output reg Q, Q_)
    > > always @(CLK) Q = D;
    > > assign Q_ = ~Q;
    > > endmodule
    > >
    > > Then say you want to reuse this module to define the JTAG
    > > version. Using upward relative references you could:
    > >
    > > module jtag_ff(input D, CLK, JTAG_D, JTAG_C, output Q, Q_)
    > > ff flip_flop (D, CLK, Q, Q_);
    > > add_jtag jt (JTAG_D, JTAG_C);
    > > endmodule
    > >
    > > module add_jtag(input JTAG_D, JTAG_C);
    > > always @(JTAG_C) ff.Q = JTAG_D;
    > > endmodule
    > >
    > > The difference here is that the add_jtag doesn't need to know the
    > > instance name of the ff it is mucking with: the rules of 12.4 require
    > > the simulator to find the nearest neighbor up the hierarchy that
    > > instanticate an 'ff' module. It does not affect every 'ff' module,
    > > just the first one found using the upwards relative refernecing rules
    > > defined in 12.4.1
    > >
    > > -mac
    >
    >I could not find the 12.4 "nearest neighbor" prescription - which document
    >are you citing? In 1364-2001 section 12.5 says:
    >
    >"It shall only search in higher enclosing modules for the name, not
    >instances."
    >
    >I understand the use of upward references to module_names to be analogous to
    >C++ class references: i.e. something you'd use only to reach static data,
    >typedefs,
    >local functions, or other entities shared by all instances of the module.
    >
    >Greg

    --------------------
    Stefen Boyd Boyd Technology, Inc.
    stefen@BoydTechInc.com (408)739-BOYD
    www.BoydTechInc.com (408)739-1402 (fax)

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