Introduction
Introduction Get started Hello UVM example UVM Phases Part 1 UVM Phases Part 2 UVM Base Classes UVM Object and Core Methods UVM Components
Building a Testbench
UVM Transaction UVM Sequence UVM Sequencer UVM Driver UVM Monitor UVM Scoreboard UVM Agent UVM Environment UVM Test
Other Components
Coverage Collector
Execution Model
UVM Phases Objections
Communication
TLM Basics TLM Blocking Put Port TLM Non-Blocking Put Port TLM Blocking Peek Port Analysis Ports TLM FIFO
Configuration
UVM Factory UVM Config DB
Runtime Control
UVM Plusargs Seeds & Reproducibility Verbosity Control Debug Runtime Controls
Advanced
Virtual Sequences Virtual Sequencer
UVM RAL
Intro Abstraction Flexibility Comparison Coverage Minimum Requirements Learning Path Register Types First Implementation Register with 2 Fields Register with Reserved Bits Access Policies Part 1 Access Policies Part 2 Access Policies Part 3 Access Policies Part 4 Memory Modeling Register Block Adapter Introduction Adapter Methods Adapter Example Predictor Types Desired and Mirror Values Register Methods Desired Value Mirror Value

UVM TLM Blocking Put

Blocking put is a fundamental UVM TLM communication mechanism where a producer sends a transaction and waits until the consumer finishes processing it before continuing execution.

Learning Objectives

  • Understand blocking communication in UVM TLM
  • Learn the roles of port, export, and implementation
  • Understand how transactions are routed between components
  • Run and analyze a working example

What is Blocking Put?

In blocking put communication, the sender calls the put() method and waits until the receiver completes the operation. The sender resumes execution only after the consumer finishes processing the transaction.

Blocking behavior guarantees ordered and synchronized transaction transfer.

Architecture Overview

Blocking put communication is built using three TLM elements. Each element has a specific responsibility in the communication chain.

Producer (Port) → Export (Forwarding) → Implementation (Consumer)

TLM Components

Blocking Put Port

The port belongs to the producer and initiates the transaction transfer. It declares the put() interface but does not implement it. 

uvm_blocking_put_port #(packet) put_port;
  • Owned by the sender
  • Calls put()
  • Contains no implementation logic
Blocking Put Export

The export forwards the transaction to another component. It enables hierarchical connections without adding behavior. 

uvm_blocking_put_export #(packet) put_export;
Blocking Put Implementation

The implementation resides in the consumer and contains the actual put() task that processes the transaction. 

uvm_blocking_put_imp #(packet, consumer) put_imp;
The producer remains blocked until this implementation finishes.

Connections and Code Behavior

p.put_port.connect(c.put_export);
c.put_export.connect(c.put_imp);

Connections are established during the connect_phase. When the producer calls put(), UVM routes the call through the connected chain until it reaches the implementation.

Port → Export → Implementation → put()

Because the call is blocking, execution returns to the producer only after the consumer's put() task completes.

Execution Flow

  1. Producer calls put(transaction)
  2. Call is forwarded through export
  3. Consumer implementation executes
  4. Method returns to producer
Blocking duration depends entirely on the execution time of the consumer’s put() task.

Verification Insight

Blocking put is commonly used between drivers, reference models, and scoreboards where transaction completion and ordering must be guaranteed.

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