VerilogA - command: $root

Hi,

One way to obtain votlages, current and other parameters is to use the $cds_get_analog_value command. Also aliased to $cgav for short.

Unfortunately you are not able to use the $root with $cgav. So instead, you can take advantage of the string manipulation commands available to you in VerilogA to retrieve the hierarchical path which can then be used in the $cgav.

Here is an example of the code you could use;

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

module getDiff1 ( );
real vdiff;

string instPath, instPath_1, instPath_cgav;
integer pn1;

    //////////////////////////////////////////////////
    //include functions needed for string manipulation
    //////////////////////////////////////////////////
    `include "shdl_strings.vams"


initial begin
    

    ///////////////////////////////////////////////////////////////////
    //Retrive the instance path to where this instance is in the design
    ///////////////////////////////////////////////////////////////////
    $swrite(instPath, "%m");

    $strobe("Path is %s", instPath);

    ///////////////////////////////////////////////////////////////////////////
    //Find the index for where the last "." was in the extracted instance path
    //////////////////////////////////////////////////////////////////////////
    //pn1=shdl_strrchr(instPath, ".");
    pn1=shdl_strrchr("%m", ".");

    ////////////////////////////////////////////////////////////////////////
    //Extract the substring from the instance path for the level above this
    ///////////////////////////////////////////////////////////////////////
      instPath_1=instPath.substr(0,pn1-1);

    $strobe("Path -1 is %s", instPath_1);
    
    ///////////////////////////////////
    //Construct the string for the cgav
    ///////////////////////////////////
    $swrite(instPath_cgav, "%s.I0.vdiff", instPath_1);

//    vdiff=$cgav("I0.vdiff", "potential");
//    $strobe("Vdiff is %f\n", vdiff);
end


always #0.5 begin

    //////////
    //Use cgav
    //////////
    vdiff=$cgav(instPath_cgav, "potential"); ;;<-- FOR CURRENT YOU CAN USE "flow" HERE
    $strobe("Vdiff is %f\n", vdiff);

end

endmodule

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

As you can see in my comments the use of the $cgav can be used to get the current by switching out the "potential" to "flow";

$cgav(instPath_cgav,"flow")

More details of using the $cds_get_analog_value can be seen in the documentation.

Kind regards

Marcel