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Course contents

  • Start Here6
  • SystemVerilog Language Foundations28
  • Object-Oriented SystemVerilog for Verification30
    • Classes, Objects & Handles
    • Inheritance and Polymorphism
    • Static, Encapsulation & Parameterized Classes
    • Virtual Interfaces: the Class-to-Pins Bridge
      • Why Virtual Interfaces Exist
      • Declaring & Binding a vif
      • Driving & Sampling via Clocking Blocks
      • vif Configuration Patterns
      • Multi-Instance & Parameterized vifs
    • Events, Semaphores, Mailboxes and Processes
    • OOP Patterns for Testbenches
  • Constraint Randomization — Interview-Critical Deep Dive36
  • SystemVerilog Assertions — Interview-Critical Deep Dive40
  • Functional Coverage in SystemVerilog22
  • Testbench Architecture in SystemVerilog23
  • Advanced Language & Integration25
  • Senior & Interview Preparation21
  • Principal-Level Verification28
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‹Object-Oriented SystemVerilog for Verification
  1. Topics
  2. SystemVerilog
  3. Object-Oriented SystemVerilog for Verification
  4. Virtual Interfaces: the Class-to-Pins Bridge

Part 2 · OOP for Verification · Intermediate

Virtual Interfaces: the Class-to-Pins Bridge

Virtual interfaces bridge classes and pins: binding, clocking drives, config, multi-port vifs.

  • 5topics
  • 5lessons

Classes are created at runtime with no pins. Interfaces are elaborated before time zero with real signals. A virtual interface is the one reference that connects them.

Two worlds and one bridge: the vif is a reference from a class object to a real interface instance.

Side

Lifetime

How it reaches pins

Static world (modules, interfaces)

Elaborated before time zero

Owns the real signals at fixed paths

Dynamic world (classes)

Created by new() at runtime

No hierarchy and no pins of its own

Virtual interface

Bound top-down after elaboration

Class property referencing one interface instance

Lesson

You will build…

Why Virtual Interfaces Exist

The static-vs-dynamic binding problem and what a vif reference stores.

Declaring & Binding a vif

Constructor binding, top-down handoff, and guards against the null-vif crash.

Driving & Sampling via Clocking Blocks

Race-free drives and samples through vif.cb, plus modport-selected vifs.

vif Configuration Patterns

Constructor chaining, one central config object, and what config_db does.

Multi-Instance & Parameterized vifs

Vif arrays for multi-port DUTs and strategies for parameterized widths.

Check yourself A driver class must touch DUT pins, but classes have no hierarchy. What bridges the two, and which way does binding flow?

A virtual interface: a class property holding a reference to one elaborated interface instance. Binding flows top-down: tb_top hands the instance into the classes, and classes never reach up for it.

Interview

“What does a virtual interface store?” expects one word: a reference. Follow-ups: null until bound, retargetable without class changes, and class drives go through vif.cb.

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See also

  • Classes, Objects & Handles
  • Inheritance and Polymorphism
  • Static, Encapsulation & Parameterized Classes