pyquesta 2.5.1

A link between Questa and Python

License

© 2022 Siemens.

This material may only be used with products of Siemens Industry Software Inc. or its affiliates, and for no other purpose.

License continued below

pyquesta module

*pyquesta provides resources for Python programmers using Questa. The first resource released is SVconduit

SVConduit

The SystemVerilog Conduit system with the SVConduit module allows a Python testbench writer to exchange an object with SystemVerilog. This allows the Python programmer to leverage Questa's advanced constraint-solver, and functional coverage and the UCDB.

SVconduit introduction

The first step to using SVConduit is to define a class using YAML. The system will generated modules that define a Python version of the class and a SystemVerilog version of the class.

Define the communication class

For example, here is a transction class (ALUCommand) that sends instructions to the TinyALU, which has two 8-bit legs and four operations.

ALUCommand:
  A:
   uchar
  B:
   uchar
  op:
   uchar

The gen_svconduit_pkgs program reads this YAML file and generates a Python module and SystemVerilog package that define the class in those languages along with the serialization methods to pass it between Python and SystemVerilog.

Commuinate with SystemVerilog from Python

This snippet of test code creates a cmd using the SystemVerilog constraint-solver and writes the command into a SystemVerilog covergroup:

from pyquesta import SVConduit
from ALUCommand import *

<snip>
    for _ in range(2):
        cmd = SVConduit.get(ALUCommand)  # get random command
        SVConduit.put(cmd)  # put in coverage
<snip>

SVConduit.get() class method knows where to get the object based on the ALUCommand class passed to it. The SVConduit.put() class method knows where to send the object based on its type.

Populate the SystemVerilog functions

The ALUCommand.sv file defines a package named ALUCommand. This package defines sv_put() and sv_get() which define the SystemVerilog behavior associated with ALUCommand objects.

The sv_get() function uses the constraint solver to randomize an ALUCommand object and return it to Python:

function string sv_get();
    ALUCommand obj;
    string obj_str;
    obj = new();
    // Insert user to populate obj
    void'(obj.randomize() with {op inside {[1:4]};});
    // User code ends. You must have populated obj
    obj_str = obj.serialize();
    return obj_str;
endfunction

The sv_put() function gets a handle to a singleton containing a covergroup and samples the command:

function void sv_put(ALUCommand_buf_t byte_buf);
    ALUCommand obj;
    obj = new(byte_buf);
    // Replace with user code for put function
    cov = Coverer::get();
    cov.A = obj.A;
    cov.B = obj.B;
    cov.op = obj.op;
    cov.op_cov.sample();
    // User code ends. You have used data from obj
endfunction

Now the Python code can get objects and send objects to the SystemVerilog package.

Learn more about SVConduit

You can get a copy of the example used in this README.md file as well as read a tutorial and documentation about SVConduit at the Verification Academy.

Full license

© 2022 Siemens.

This material may only be used with products of Siemens Industry Software Inc. or its affiliates, and for no other purpose.

If you have a signed license agreement with Siemens for the product with which this Software will be used, your use of this Software is subject to the scope of license and the software protection and security provisions of that agreement. If you do not have such a signed license agreement, your use is subject to the Siemens Universal Customer Agreement, which may be viewed at https://www.sw.siemens.com/en-US/sw-terms/base/uca/, as supplemented by the electronic design automation (EDA) specific terms which may be viewed at https://www.sw.siemens.com/en-US/sw-terms/supplements/.

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