VHDL verilog mixed design, strange problem

Discussion in 'VHDL' started by Akshaye, Feb 6, 2004.

  1. Akshaye

    Akshaye Guest

    Hi,

    I had this wierd issue with vhdl-verilog co-simulation.

    I have a net which is driven in VHDL and is used as an input to 2
    verilog designs which are instantiated in this VHDL block.

    |-----
    |----->|verilog A
    | |-----
    VHDL ----|
    | |-----
    |----->|verilog B
    |-----

    The net is directly used on ports on the verilog modules. Now if i
    assign this internal net in "verilog A" module via PLI, a strange
    thing happens in the simulator. The net inside verilog A is assigned
    this value, the net inside verilog B is assigned this value(wierd?)
    but the top level net in VHDL does not get this value!

    I have no issue with the VHDL net not getting the assigned
    value(because its direction is opposite), but what complicates
    debugging is that it is assigned in verilog B.

    Is this some optimisation in the simulator which moves this net node
    from VHDL to verilog possibly to reduce VHDL to verilog boundary
    signals? Can somebody provide an expaination for this? is it simulator
    dependent?

    Thanks in advance.
     
    Akshaye, Feb 6, 2004
    #1
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  2. Akshaye

    Hemant Gupta Guest

    This should be simulator dependent.

    regards,

    Akshaye wrote:

    > Hi,
    >
    > I had this wierd issue with vhdl-verilog co-simulation.
    >
    > I have a net which is driven in VHDL and is used as an input to 2
    > verilog designs which are instantiated in this VHDL block.
    >
    > |-----
    > |----->|verilog A
    > | |-----
    > VHDL ----|
    > | |-----
    > |----->|verilog B
    > |-----
    >
    > The net is directly used on ports on the verilog modules. Now if i
    > assign this internal net in "verilog A" module via PLI, a strange
    > thing happens in the simulator. The net inside verilog A is assigned
    > this value, the net inside verilog B is assigned this value(wierd?)
    > but the top level net in VHDL does not get this value!
    >
    > I have no issue with the VHDL net not getting the assigned
    > value(because its direction is opposite), but what complicates
    > debugging is that it is assigned in verilog B.
    >
    > Is this some optimisation in the simulator which moves this net node
    > from VHDL to verilog possibly to reduce VHDL to verilog boundary
    > signals? Can somebody provide an expaination for this? is it simulator
    > dependent?
    >
    > Thanks in advance.
     
    Hemant Gupta, Feb 9, 2004
    #2
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