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Using strings in constraints to randomize data

PSAM

Hi,

 I am using a constraint that uses a string var to randomize a random variable(data). But xcelium give me an error:

Constraint:

constraint data {
    sel_string inside {"A"} -> data[0] == 1;}

Error:

xmvlog: *E,WOUPYR (): As a temporary implementation restriction, string is not permitted in this context.
 |     sel_string inside {"A"} -> data[0] == 1,

Any suggestions, how to get around this?

Thanks,

Preethi

  • One way to work around this is to convert the string variable to a SystemVerilog enumeration. The following code snippet illustrates this.

    typedef enum {A, B} sel_string_e;

    class foo;
    rand sel_string_e sel_string;
    rand bit [2:0] data;
    constraint data_c {
        //sel_string == A -> data[0] == 1;}
        sel_string inside {A} -> data[0] == 1;}
    function void printme();
        $display("sel_string is : %s", sel_string.name);
        $display("data[0] is : %d",data[0]);
    endfunction
    endclass

    module test;
      initial begin
        foo foo_i = new();
        void'(foo_i.randomize());
        foo_i.printme();
      end
    endmodule

    The following article talks about this in more detail.

    https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1Od0000000nTeVEAU&pageName=ArticleContent&sq=

    "Using strings in constraints results in ncsim: *E,RNCTYP: A 'string type' cannot be used within a constraint expression"

  • in reply to muffi

    Hi,

    Thanks for this solution. The compilation error is gone.

    Thanks,

    Preethi

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