The Evolution of Function Blocks in Industrial Automation
Discover the history and legacy of this Brazilian technology.
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The Evolution of Function Blocks in Industrial Automation: From the Configurable Structure of the Smar CD600 to the Open Global Standard O-PAS
The history of industrial automation is marked by the continuous transition from proprietary and rigid systems to open, modular, and interoperable architectures. At the epicenter of this evolution, the Brazilian company Smar, founded in 1974, played a fundamental role in introducing concepts that would shape international process control standards. The technological trajectory of the Function Blocks, developed by Smar, begins with the CD600 multi-loop controller, is consolidated through the distributed architecture of the System302, and culminates in an unprecedented contribution to the global industry: the transfer of its algorithm library for the composition of the O-PAS (Open Process Automation Standard), under the aegis of the Open Group. This evolution reflects not only the progress of computing applied to control, but also a philosophical paradigm shift in engineering, where the value of software is enhanced by its ability to run on hardware-independent platforms.
The Technological Foundation: The CD600 Multi-Loop Digital Controller
The emergence of the Smar CD600 in the 1980s represented a watershed moment for process control in Brazil and worldwide. At a time when most controllers were dedicated
to a single control loop, the CD600 introduced the ability to simultaneously process up to four complex loops with a single piece of hardware. The architecture of this equipment was built on the innovative concept of "free blocks," a library of pre-programmed algorithms that could be interconnected according to the user's control strategy needs.
Software Architecture and the Free Block Concept
Programming the CD600 did not require in-depth knowledge of low-level programming languages. Instead, the user configured the controller through an interface of functional blocks residing in the equipment's non-volatile memory (NVRAM). Programming consisted of uploading these blocks to working memory, establishing links between them, and adjusting characterization parameters to adapt them to specific applications.
Each functional block in the CD600 had a control function composed of mathematical or logical operations that related its inputs to its outputs. The inputs were identified by letters (A, B, C...) and the outputs by numbers, which functioned as unique memory addresses. The link parameter (L) was key to connectivity: assigning an output number to an input link parameter (such as LIA, LIB, or LIC) created a virtual data link between the blocks. This logical structure allowed the creation of highly sophisticated control strategies that previously would have required the physical wiring of multiple analog instruments.
Versatile Application and Advanced Control
The CD600 was designed to replace a wide range of panel instruments, including single-loop controllers, manual stations, setpoint programmers, and flow computers. With over 120 control blocks available, the device was capable of executing strategies such as:
- Three-element boiler level control (water, steam, and level);
- Cross-limit combustion control;
- Control of distillation columns;
- Feed-forward and ratio control strategies.
The interface with the physical world occurred through analog and digital input and output blocks, directly linked to the terminals of the controller's terminal block. For example, analog input block #001 processed the signal coming from the corresponding physical terminal, digitizing it for use in the internal strategy. This modularity allowed a single unit to replace up to eight traditional controllers, drastically reducing panel space and cabling complexity.
Configuration Tools and Interface
To manage this vast library of blocks, Smar developed software such as CONF600 and, later, CONF600Plus. These tools provided a graphical interface that facilitated the visualization of the control strategy, allowing fine-tuning of PID parameters, time constants, and alarm limits. Adjustments could also be made directly from the controller's front panel, which featured an 8-digit alphanumeric display and an integrated alarm station, ensuring that the operator had complete control over the process even without the aid of a computer.
The Transition to Distributed Automation: The Emergence of System302
With the evolution of communication technologies and the strengthening of the Foundation Fieldbus protocol in the 1990s, Smar began migrating its expertise in function blocks to a fully distributed architecture: the System302. While in the CD600 the blocks were centralized in a single piece of hardware, in the System302 the control came to reside in the field devices themselves, such as transmitters and positioners.
Field Control and Interoperability
The System302 was designed as a Fieldbus control system where time-critical functions were primarily performed on field devices. This paradigm shift allowed measurement, control, and actuation tasks to be distributed throughout the industrial plant, reducing reliance on central controllers and increasing system robustness.
Interoperability became the central pillar of this phase. Thanks to the use of Device Description (DD) technology, Smar devices could communicate seamlessly with equipment from other manufacturers on the same Fieldbus network. The function block library was expanded and adapted to meet Fieldbus Foundation specifications, including blocks such as Analog Input (AI), PID, and Analog Output (AO), which underwent rigorous interoperability testing.
Enhancements to the Function Block Library
Smar did not limit itself to following basic standards; it developed "Advanced" and "Enhanced" blocks to fill functional gaps identified in the field. The technical evolution of these blocks in the System302 included:
An innovative feature introduced in System302 was the dynamic instantiation and deletion of blocks. Unlike systems where the number of blocks was fixed by hardware, the System302 user could define which and how many blocks would be created on each device at the time of configuration, optimizing memory usage and instrument processing capacity.
The DFI302 Platform
The nerve center of System302 was the DFI302 distributed field interface. This device acted as a network master and multifunctional controller, capable of integrating protocols such as Foundation Fieldbus, Profibus, Modbus, and HART. The DFI302 allowed complex control strategies to be configured by interconnecting function blocks from different devices into a single logical strategy, consolidating the "ONE PLANT, ONE SYSTEM" vision.
The mathematical processing in these blocks evolved to support high-precision calculations. For example, the arithmetic block (ARTH) allowed the implementation of flow compensation formulas using scientific notation and complex operators:
Where:
- Q comp is the compensated flow rate.
- K is the constant of proportionality.
- D P is the measured differential pressure.
- P is the absolute pressure.
- T is the absolute temperature.
These formulas were encapsulated in easy-to-use function blocks, abstracting the mathematical complexity for the automation engineer.
Technological Expansion: Licensing and Supply to other Manufacturers
A crucial step in Smar's trajectory was the transition from a hardware manufacturer to a technology provider for the global market. During the consolidation of System302 and Fieldbus networks, Smar began supplying and licensing its "Communication Stack" (FBStack) and its library of functional blocks to other automation companies and instrument suppliers.
Through flexible licensing models—ranging from the use of object libraries to source code buyouts—competing manufacturers were able to incorporate Smar's proven technology into their own products. This allowed third-party instruments to natively execute the control algorithms and communication protocols developed in Brazil, ensuring agility in the development of new solutions and strengthening the interoperability ecosystem. This model of collaboration and technological openness was the direct precursor to the culture that would lead Smar to contribute its library to the foundation of the global O-PAS standard.
The Era of Open Automation: Contribution to the O-PAS
The evolution culminated in a historic move in the 2020s: the integration of Smar technology into the O-PAS (Open Process Automation Standard). O-PAS is a standard developed by the Open Process Automation Forum (OPAF), which aims to create an open, secure, and interoperable reference architecture, allowing components from different vendors to work together natively.
The Role of Smar in Setting the Standard
Smar has actively participated in the definition and validation activities of O-PAS from the beginning. In an unprecedented gesture of technical cooperation, the company contributed its proven library of function blocks for the development of the new technology, serving as the basis for the standard blocks of the O-PAS standard.
This concession means that the control algorithms, refined over decades since the CD600 and System302, have become the foundation for global interoperability between controllers from different manufacturers. The O-PAS standard uses Smar's function block information model to ensure that a control strategy developed in one system is perfectly portable to another, without the need for re-engineering.
O-PAS Architecture and the Distributed Control Node (DCN)
The O-PAS architecture introduced the concept of the Distributed Control Node (DCN), which acts as the basic unit of control and I/O. The DCN is responsible for acquiring process inputs, executing regulatory control through function blocks, and communicating via open protocols such as OPC UA.
In Smar's view, the System302 architecture, based on DFI302, was already fully compatible with the concepts proposed by O-PAS. The transition involved decoupling the hardware and control software, allowing the logic of the function blocks to run in containers (such as Docker) on standard operating systems, such as Linux.
The NOVA O-PAS Line
To materialize this new reality, Nova Smar launched the NOVA line, designed specifically under the O-PAS principles. This Smar brand line includes:
- NOVA DCN: A high-performance hardware solution equipped with Intel Atom® x6200FE processors, which acts as a distributed control node and gateway for legacy networks such as Foundation Fieldbus, HART, and Profibus;
- NOVA ENGINE: The function block execution software that allows you to run control strategies on virtual platforms or third-party hardware;
- NOVA FB: The library of standardized function blocks, inherited from over 40 years of field use, is now compatible with O-PAS information models;
- NOVA CSB: A web-based configuration tool that uses AutomationML (AML) files to describe plant topology and control logic, ensuring full application portability.
Technical Details of the O-PAS Block Library (SmarFB)
The library of function blocks provided by Smar and integrated into O-PAS, commercially known as SmarFB, is categorized according to its function within the control strategy. Each block has a standardized data structure that includes process values, status, configuration parameters, and limits.
Input and Output Blocks
Process interface blocks are fundamental for digitizing analog signals and managing discrete states. Compliance with O-PAS ensures that these blocks maintain the same behavior regardless of the hardware on which they are executed.
Control and Calculation Blocks
This category contains the system's "intelligence." The PID block, for example, follows the information model defined in O-PAS Part 6.4, including critical parameters such as the current error, engineering units, and range limits.
The flexibility of these blocks allows for cascaded control implementation with automatic synchronization between master and slave blocks. When a PID block sends a signal to an AO block, they perform a digital "handshake":
- The AO block reports its state through the BKCAL_OUT parameter;
- The PID block receives this information in the BKCAL_IN parameter;
- This ensures that if the output device is in manual mode, the control block stops accumulating integral error (preventing reset windup) and maintains a smooth transition to automatic mode.
Transducer and Resource Blocks
For complete lifecycle management of industrial assets, Smar has incorporated hardware diagnostic and configuration blocks. The Resource Block (RS) describes the specific characteristics of the physical device, while the Transducer Block (TRD) manages the interface with pressure, temperature, or valve positioner sensors. Advanced diagnostics are provided by the Diagnostic Transducer (DIAG), which monitors block runtime and network link integrity.
Strategic Implications and Quality Attributes
The adoption of Smar's function block technology by the O-PAS standard was driven by 23 essential quality attributes for modern automation. These attributes define the added value of an open system compared to proprietary solutions of the past.
Interoperability and Interchangeability
Interoperability is the ability of two or more systems to exchange information and use the exchanged data. In the context of function blocks, this means that a PID block from one manufacturer can receive the value of a process variable from an AI block from another manufacturer via the OCF (O-PAS Connectivity Framework) network, using the OPC UA protocol as a carrier.
Interchangeability goes a step further: it's the ability to replace a hardware component with an equivalent one from a different vendor without needing to modify the control strategy. This protects the end-user's investment against forced obsolescence and allows for the selection of the best components from each category to compose the final solution.
Portability and Modularity
One of the biggest challenges solved by standardizing Smar function blocks in O-PAS was configuration portability. Through the use of neutral languages such as AutomationML (IEC 62714), control strategies can be exported from one engineering tool and imported into another.
Modularity ensures that changes to one system component have minimal impact on the others. Thanks to the function block structure, it is possible to update the control algorithm of a specific loop without affecting the processing of other loops running on the same DCN.
Cybersecurity and Sustainability
In a world where connectivity is ubiquitous, cybersecurity (securability) has become mandatory. The O-PAS standard incorporates the IEC 62443 standard to guide the secure operation of automation systems. The function blocks operate within this secure environment, where data access is authenticated and communications are encrypted via OPC UA.
From a sustainability perspective, the O-PAS CapEx model, adopted by Smar, proposes a lower initial investment with frequent incremental improvements. Unlike traditional systems that require lengthy shutdowns for complete upgrades ("rip and replace"), the O-PAS-based system allows for continuous improvements without significant process interruptions.
From Field to Cloud: The New Frontier of Automation
The journey of Smar's function blocks doesn't end with standardization. It expands to the new frontiers of Industry 4.0 and the Industrial Internet of Things (IIoT).
Virtualization and Edge Computing
With Smar's NOVA line, function blocks are no longer prisoners of proprietary hardware. Through the "flex blocks" concept, users can download customized control applications for Smar controllers, similar to downloading apps on smartphones. These blocks can run on local servers (on-premise) or even in cloud instances, allowing for remote monitoring and management of globally distributed assets.
Ethernet-APL (Advanced Physical Layer) technology complements this evolution, bringing the high speed of Ethernet directly to field devices in classified areas. This removes the communication bottlenecks that limited the complexity of function block strategies in the past, enabling the massive transmission of diagnostic data and process variables in real time.
Education and Technological Dissemination
Recognizing that the transition to open systems requires a new technical mindset, Smar invested in the development of the world's first portable O-PAS educational kit. This kit allows engineers and academics to train with the real tools of the future—DCNs, gateways, and SmarFB libraries—facilitating a practical understanding of interoperability and function block-based configuration.
Furthermore, Smar's O-PAS Integrated Operations Center serves as a "living lab" where users can test integration scenarios between legacy systems and new open technologies, ensuring a safe and efficient migration to future standards.
Conclusions on the Trajectory of Block Technology
An analysis of Smar's technological evolution reveals a consistent pattern of innovation that prioritizes functionality over hardware rigidity. The CD600 controller established the logical foundation with its "free blocks," proving that industrial complexity could be tamed through software modularity. The System302 expanded this logic to the field, demonstrating the benefits of distribution and network interoperability.
The culmination of this process in O-PAS is perhaps the most transformative event in contemporary industrial automation. By contributing its library of function blocks, Smar not only contributed to the creation of a global standard, but also redefined its role in the market: from a controller manufacturer to a supplier of universal control technology.
The function blocks, now standardized in the O-PAS standard, are the result of four decades of field experience, millions of operating hours, and the continuous refinement of algorithms for the most severe process conditions. They represent the guarantee that the accumulated knowledge in Brazilian control engineering now benefits the entire global industry, supporting a vision of automation that is, by definition, open, safe, and without borders.
ADRIANO MARCELO CORTEZE
NOVA SMAR S/A
23/JAN/2026
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