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Institute Mihailo Pupin
Institute Mihailo Pupin is the leading Serbian R&D institution in the field of Information & Communication Techologies.

Automation & Control Systems Ltd
The Automation & Control Systems Ltd is the core division of the Institute Mihailo Pupin, and the owner of the projects: ATLAS Systems and ATLAS-MAX.

The long list of the Institute's references and customers is the best proof of its high professional and techological achievments.

The other related IMP project: VIEW4 Software Package for control of complex processes

You are here:     ATLAS-MAX System Specification ATLAS-PT PLC Specification
ATLAS-MAX Programmable Logic Control


One of the major advanced ATLAS-MAX feature is its inherent programmable logic control functionality (PLC functionality), which is usually dedicated to other kind of devices and equipment, known as Programmable Logic Controllers – PLCs.  This is a significant step in proper closing of the process control loops, that made a real difference and opened doors for implementation of ATLAS equipment in new process control areas.  These are also the main recognizable characteristics (RTU + PLC functionalities) of the last generation ATLAS Programmable Remote Terminal Systems ATLAS-MAX and ATLAS-MAX/RTL.

PLC data processing presents a complex job that consists of many preparation and control execution tasks:

  • Interactive build-up of control algorithms.
  • Real-time online process data validation and analysis toward implemented control algorithms.
  • Provision and delivery of proper control data.
  • Internal and external data check-ups.
  • Smart control decision making - prevention of wrong doing.
  • Self-testing and online diagnostics.
  • Warning and alerting.

The first, and definitely the most challenging, step presents the interactive build-up of the PLC control algorithm to be implemented.  There are several standardized programming techniques for that purpose – they are known as PLC languages defined within IEC 1131-3 standard.  ATLAS fully complies with the IEC PLC language standard, and supports:

  • Ladder Diagram (LD) - a graphical language based on ladder programming, a technique that has evolved from the electrical wiring diagrams that were used in the car industry for describing relay control schemes.  Nowadays, it is widely used for general PLC programming.  The written programs and the way they are presented resemble to “ladders”, and that is where the name of the LD language came from.
  • Functional Block Diagram (FBD) - another graphical language that contains a large library of functional blocks, starting with simple logical blocks: AND, OR, NO, XOR, FF, COUNTERS, SHIEFTS ..., up to the very complex control blocks.  FBD language allows easy wiring and connection of existing functional blocks and creation of very complex control algorithms.  FBD reminds in many aspects to electrical circuits and electronic schematics designing tools, and similarly include full support for emulation, data validation, functional testing and error detection.
  • Structured Text (ST) - a high level textual Pascal like programming language, which is very flexible and intuitive for writing control algorithms.  It uses “programming operators” such as logical branching, multiple branching, and loops.  Many trained programmers often find ST language as the easiest PLC programming tool to work with.  When symbolic addressing is used, ST programs resemble sentences, making it highly intelligible to beginner users as well.

Whatever PLC programming language is used, the programming procedure itself is performed out of the ATLAS-MAX device.  Once a PLC program is complete, the final compiled PLC control code is uploaded into the ATLAS flash memory and integrated into the overall ATLAS application.  The uploaded PLC code becomes a part of the ATLAS operational firmware until the next PLC reprogramming.  The available dedicated Programming Terminal ATLAS-PT is used for this purpose, and it is fully equipped with tools for mutual PLC language translations and diagram conversions, code compilations and uploads.

The most sophisticated and advanced part of ATLAS-PT software is the ATLAS PLC Programming Tool, the PLC FBD Package that consists of multiple graphical tools, developed and written in TCL on Linux OS platform.  The central piece of the FBD Package is: FBDE (Function Block Diagram Editor), which is a ladder editor compliant with the standard IEC 1131-3.  Other available tools and utilities support: ladder translation into ST code, compilation into ATLAS executable code, ladder simulations, ladder debugging, online testing and application code uploads.

PLC programming is organized within individual PLC projects, with ladder diagrams designed and developed for specific ATLAS units.  Consequently, at the very beginning, FDB Package is invoked with a single mandatory argument, the "PLC Project Name".  Upon successful authentication and authorization procedures, and ATLAS unit selection, the MAIN PLC MENU is opened:


Two of the listed topics are of special interest: