May/June 2010

Automation IT

Unraveling PAC

Programmable Automation Controllers: Finding common ground and determining where there are differences

Fast Forward

  • What is a Programmable Automation Controller (PAC)?
  • How do suppliers define a PAC?
  • What advantages does a PAC provide?

The term Programmable Automation Controller (PAC) has been used for over eight years with a few companies claiming to have invented the term.  The term refers to more powerful controllers, but the term PAC continues to be imprecise since there is no industry standard to use as a benchmark.  InTech asked a number of suppliers to provide their definition of a PAC-to find common ground and determine where there are differences-and for one example of a product the vendor provides that fits their PAC definition.  This is a summary based on the responses. pac11

Opto 22

PACs are the latest generation of industrial controllers that combine the features and capabilities of PC-based control systems with those of traditional programmable logic controllers (PLCs).  PACs fill an increasing need for compact, powerful hardware devices that perform traditional PLC-type functions plus offer data acquisition capabilities.  PACs utilize a variety of standard network interfaces and protocols including wired and wireless Ethernet, TCP/IP, OPC, and SMTP achieving a high degree of enterprise connectivity and integration with enterprise applications and databases.  The PAC is a multi-disciple integrated control and communications platform programmed with flexible, general purpose, and straightforward programming techniques, making PAC programming easier to learn and understand.  PLCs are programmed via different flavors of the IEC 61131-3 languages, some of which remain largely esoteric (e.g., relay ladder logic.)   PACs utilize a single tag name database and global logical memory to identify, map, and address I/O points more easily.

-David Crump, Marketing Communications Manager,

PAC Opto 22 SNAP Programmable Automation Controller

National Instruments

The PAC has the ruggedness of a PLC combined with processing power of a PC.  The PAC is programmed with easy to understand graphical programming.  The PAC has a diverse set of I/O available including high speed I/O particularly analog.  PACs shine at advanced functions including advanced control, predictive maintenance, gauging, vibration analysis, and embedded data logging.  Extremely high speed functions are implemented using FPGA technology in the PAC architecture that is configured with graphical programming.   The PLC is suited to mostly smaller digital applications.  PLCs that simply have more memory or point capacity are not a PAC.  The PAC has significantly more processing power for advanced control and automation.

-Irene Bearly, Product Manager for Industrial Communication,

National Instruments NI cRIO-9025 Programmable Automation Controller


The PAC is the next progression of the PLC, merging all functions in a high performance multi-controller computing platform, programmed using object oriented symbolic software that allows reuse of all or pieces of application programming.  The PAC has greater logic handling capabilities to handle cyclic-events for PLC logic, sequential-events for motion logic, timer-events for communication and data management, interrupt-events for quick response to high-speed inputs, and deterministic-events (down to 250µs) for adaptive position corrections.  PLCs require multiple hardware components for machine control, where one PAC can handle PLC logic, motion control, drive control, motion safety, robotics, and PID control.  Additional functions can be enabled in a PAC simply with software.  Using a PAC greatly reduces panel space, wiring, and simplifies (and sometimes eliminates) field-bus configuration. PLC application programming is not portable since it is tied to the hardware. 

-Zuri Evan, Product Manager, Simotion,

Siemens Simotion D - Programmable Automation Controller

Beckhoff Automation

Beckhoff defines a PAC as an embedded PC programmed with integrated development software.  The PAC is a multi-functional controller with logic, motion, visualization, multiple communications protocols, and data management all handled in one central processing unit (CPU).  A PAC accomplishes its tasks using software and abstracts from the hardware level.  The PAC provides the same functionality as a traditional PLC and then extends functions to deliver a complete solution by adding software modules on top of the base system.  The system becomes platform-independent enabling applications investment to growth with hardware advances removing the fear of hardware obsolescence.  Still some engineers think only PLCs can provide small form factors, but this is not the case anymore with technology to make incredibly small high-performance embedded PC controllers (PAC), incorporating Windows CE as the operating system (which is a real-time OS).

-Graham Harris, President,

Beckhoff CX1010 and CX1020 Series Programmable Automation Controller

Ascon Corporation

Ascon defines a PAC as a cross between a PLC and PC, bringing together the processing capability of a PC with the industrial uses of a PLC. In addition, the PAC adds stronger process control that typically a PLC does not have.  A PLC is more specialized in digital functions with some added capability for analog processing.  Ascon's PAC is specialized in analog processing capability with included functions for digital and sequence control (logic).  Select a PAC if the user needs stronger process control over just digital I/O functions of a PLC. PAC products have powerful PID, auto-tune, and math capabilities that might not be available in a PLC, or available only in very high-end PLC and distributed control system products.

-Steve Rakers, President,

ASCON microPAC Programmable Automation Controller


Advantech defines a PAC as a controller, which utilizes open technologies (many of which are de-facto standards) for hardware and software designs. For example, PAC hardware often includes popular CPUs from leading providers like Intel.  PAC software choices are vast as programmers can choose between IEC 61131-3, Visual Studio.NET, Embedded Visual C++, and many other third party development environments, all while using the same PAC open standards hardware. PACs provide more tools to integrate various aspects of the application including strong communication connectivity, best in class CPU performance, and easy enterprise integration with open standard technologies.  The PAC integrates control, information processing, and networking in a single platform and can provide dual controllers for different tasks with deterministic performance.  All these features make PACs more reliable, scalable, and flexible, satisfying various complicated control and automation applications.

-Chuck Harrell, Direct Marketing,

Advantech APAX-5000 series Programmable Automation Controller

Rockwell Automation

The PAC is an evolution of the PLC that is a controller platform that encompasses hardware and software.  It is a multidiscipline controller integrating control disciplines including discrete, motion control, and process control, plus integrating all forms of network communication. PAC software has a single tagged-based software environment that supports multiple control languages.  It provides scalability and application portability within an open, modular architecture all designed to work seamlessly.  This architecture provides a single, multi-disciplined control platform for applications that span the entire plant floor, all within with a single hardware and software platform.

-Scott Tenorio, Marketing Manager, Controls & Visualization Business; Dennis Wylie, Product Manager,

Rockwell Automation ControlLogix L7 Programmable Automation Controller

B&R Automation

A PAC encompasses the functionality of a PLC, motion controller, CNC/robotics controller, Visualization/HMI capability, and communication capabilities.  A PLC is just one part of the functionality contained in a PAC.  The additional functional areas mentioned here would typically be handled with separate hardware in a traditional PLC architecture.  A PAC combines these capabilities into a single piece of hardware.

-Corey Morton, Engineering Manager, B&R North America,

B&R APC810 Automation PC  Programmable Automation Controller

GE Intelligent Platforms

PACs are powered by a single, portable control engine; handle multi-disciplined control logic, motion control, HMI, and process control; and support distributed I/O through standards-based communications.  PACs use a single integrated programming environment for development of multiple applications, significantly reducing the amount of time and effort needed to synchronize multiple programs.  Users choose the hardware and programming language that best suits each particular application. A PAC's functionality is rooted in its portable control engine with each application interfacing independent of the deterministic operating system of choice, enabling the platform to grow and change as rapidly as user needs demand.  Few changes are required to move applications from system to system.  PACs employ de facto standards for network interfaces and languages to allow data exchange as part of a networked multi-vendor system. 

-Tyler Croft , Product Marketing Manager,

GE Intelligent Platforms RX3i Programmable Automation Controller


The term PAC is simply a marketing term that was created in an attempt to differentiate hardware due to the commoditization of the "traditional" PLC. I don't know that it benefits the engineering community to classify controller hardware/software with another buzz word.  Currently PLCs are categorized by I/O sizes, nano: 32, micro: 33 -128, small: 129-512, and large, over 512 I/O as PLC vendors try to distinguish the products within these categories.  Let the controls engineer define what he or she needs rather than try to define and market PLCs based on I/O count and consequently size or price. Controls Engineers are more than capable of defining their application needs and selecting an appropriate control platform.  Small footprint, low cost PLCs now have the power and I/O count of a large PLC and powerful specialty modules including functions like stepper control, power measurement, and vibration analysis.

-Dean Norton, Marketing Manager,

WAGO 750-841 Programmable Automation Controller

Phoenix Contact

PACs combine the best of the PLC world with the best of the PC world. They combine secure PLC control functions with PC-based performance, capacity, and connectivity features. Many PACs feature local I/O expansion options with direct connection to a modular I/O system. PACs with integrated Ethernet ports support popular protocols such as MODBUS TCP or EtherNet/IP. 

-Bjoern Falke, Product Marketing Lead Specialist for Automation,

Phoenix ILC 170 Programmable Automation Controller

Schneider Electric

PACs offer the advantages of PLC deterministic machine or process control with the flexible configuration and enterprise integration strengths of PC-based systems supporting functions including coordinating remote monitoring, data acquisition simple interfaces with HMIs, Ethernet,TCP/IP, web services, and SNMP.  The PAC is a single reliable platform running a real-time operating system that can control motion, drive, logic, and process control all on one platform.  The PAC is easily networked with automation devices, other PACs, and existing enterprise infrastructure.   The PAC often provides inherent algorithms for tackling modern control scenarios such as PID and process loops.  PACs utilize off-the-shelf components common to commercial PC equipment such as cabling and memory cards to setup, upgrade, and maintain the system.

-Robert Konermann, Product Marketing Manager - Drives, Soft-Starts, Motion & HMI,

Schneider Modicon M340 Programmable Automation Controller

Mitsubishi Electric

The term PAC refers to a manufacturing platform.  Mitsubishi Electric offers a PAC Manufacturing Platform that supports all control disciplines such as Sequence, Motion, Robot, CNC, and PC.  Customers can pick and choose the best control disciplines for each application while leveraging the same software, I/O, communication interfaces, power supplies and backplanes.  The backplane of a PAC should have a direct connection for the HMI without the need of additional network components and last but probably the most important; a PAC has to have the ability to connect directly to the information technology (IT) assets without leveraging middleware like OPC/visualization software and gateway computers.  Any PAC that does not provide this flexibility is really nothing more than a legacy PLC or motion controller with a couple of new features. Superior performance, improved maintainability, and significant cost savings are all realized by PAC Manufacturing Platforms from Mitsubishi Electric.

-Sloan Zupan, Product Marketing Manager,

Mitsubishi MES Interface IT Module

Conclusions and thoughts

The major benefits of a PAC appear to be integration of multiple control functions on a powerful hardware platform with object oriented symbolic programming and open communications. 

The PAC term is not precise, but it does seem to define a more powerful category of controllers that have grown beyond simple PLCs.  PACs are certainly not a generally open architecture with a de facto operating system and standard hardware architecture like the PC (Windows; PCI bus).  It should be noted there are some PAC vendors with products that support PCI and PCI Express standard architecture.
The reuse of software was put forward as a strength, but this is only possible when a user commits to a specific vendor's architecture or where vendors adhere to software standards that enable portability.  The only open standard for interchange of symbolic control programs is the PLCopen XML interchange standard.

One way to leverage the advantages of PAC architecture is to standardize on a product from one particular PAC vendor that has a strong offering and native interfaces to open networks important in your applications.  Networks may include Modbus, DeviceNet, PROFIBUS, EtherNet/IP, PROFINET, ASi, EtherCAT, POWERLINK, SERCOS, Foundation Fieldbus, HART, and safety networks.  The alternative to native interfaces is to use network protocol gateways.

Success in an application is still primarily tied to the engineer's definition of the requirements and selection of hardware and software that will do the job.  Control requirements in many cases have broadened  to include optimization, diagnostics, and enterprise data interchange.  The good news is there are more powerful options at lower cost.

Source: This article was complied by Bill Lydon (, InTech's chief editor.  Please share your thoughts and experiences with PACs.