block

Discussion in 'VHDL' started by Mike Treseler, Apr 8, 2004.

  1. "Steve" <> wrote in message news:<c516s3$96f$>...

    > Why do people use the block command in VHDL? For example:
    >
    > state_machine : block
    > etc
    > etc


    It would allow you to limit the scope of
    signals and other declarations that would
    otherwise span the architecture.

    I find it less trouble to use a variable
    in process scope for this purpose.

    I have never seen a block statement
    used outside of a textbook except
    as a band-aid for vhdl-87 generate statements.

    I expect that someone has found a good use for it.

    -- Mike Treseler
    Mike Treseler, Apr 8, 2004
    #1
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  2. Mike Treseler

    Steve Guest

    Hi,

    Why do people use the block command in VHDL? For example:

    state_machine : block
    etc
    etc

    I've done a search in google but can find no answers. I was wondering what
    affect it has on the code.

    Thanks,
    Steve, Apr 8, 2004
    #2
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  3. Mike Treseler

    Jim Lewis Guest

    Block statement in its simple form creates a
    logical level of hierarchy in the VHDL code.
    With synthesis commands you can force this to become
    an actual level of hierarchy. I have used this
    to partition logic that ran into synthesis issues.

    Realistically I only use it reactively for
    troubleshooting.

    Cheers,
    Jim

    --
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Jim Lewis
    Director of Training mailto:
    SynthWorks Design Inc. http://www.SynthWorks.com
    1-503-590-4787

    Expert VHDL Training for Hardware Design and Verification
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Steve wrote:
    > Hi,
    >
    > Why do people use the block command in VHDL? For example:
    >
    > state_machine : block
    > etc
    > etc
    >
    > I've done a search in google but can find no answers. I was wondering what
    > affect it has on the code.
    >
    > Thanks,
    >
    >
    Jim Lewis, Apr 8, 2004
    #3
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