NTX Logic


NTX Logic is a programming application that runs on the NTX Series substation controllers to provide powerful and sophisticated capability for running local control processes.  It combines ladder logic capability with powerful function blocks to give you the simplicity of a PLC with the performance of a high-end process controller.  


The NTX Logic programming environment  is based on the industry standard Application Workbench from ISaGRAF ( and supports all of the standard IEC 61131-3 languages, as well as Flow Chart.  This flexibility enables the user to choose the language that best suits their knowledge, style and the nature of the application. Tools are provided for editing, debugging, code generation, documentation, library management, archiving, on-line monitoring, off-line simulation and on-line changes.  The application provides powerful and intuitive graphical and textual editors, including docking toolbars and resizable split windows, drag-and-drop and cut-and-paste to enhance ease of use.


NTX Logic supports the following IEC 61131-3 languages:

  • SFC: Sequential Function Chart 
  • FBD: Function Block Diagram 
  • LD: Ladder Diagram 
  • ST: Structured text 
  • IL: Instruction List 
  • FC: Flow Chart



Sequential Function Chart (SFC) 

Sequential Function Chart (SFC), the core language of the IEC 61131-3 standard, divides the process cycle into a number of well-defined steps, separated by transitions. The other languages are used to describe the actions performed within the steps and the logical conditions for the transitions. The SFC has a Graphic User Interface (GUI) to color-coded chart elements in an easy-to-use grid for element insertion, selection and movement. During the development, the chart is automatically rearranged to provide a clean display. 


Function Block Diagram (FBD) 

Function Block Diagram (FBD) is a graphical language that allows the user to build complex procedures by taking existing function blocks from the library, and wiring them together on screen. The diagrams are color-coded and can be zoomed into view the whole diagram or specific areas in more detail.


Ladder Diagram (LD)

The Ladder Diagram (LD) is one of the most familiar methods of representing logical equations and simple actions. Contacts represent input arguments and coils represent output results. The Quick LD editor provides the best compromise between high-level graphic capabilities and easy-to-use keyboard driven programming. Each block in the selection list has a description text with the option for manual text input from the keyboard. The user can mix LD and FBD programming in the same chart.


Structured Text (ST) 

Structured Text (ST) is a high-level structured language with a syntax similar to Pascal but more intuitive to the automation engineer. This language is primarily used to implement complex procedures that cannot be easily expressed with graphical languages (e.g. IF / THEN / ELSE, FOR, WHILE...). The ST Editor guides the user to the correct syntax and punctuation. 


Instruction List (IL)

The Application Workbench also includes Instruction List (IL), a low-level Boolean language similar to the simple textual PLC languages that are programmed at the register level.


Flow Chart  

The Flow Chart is an easy to read decision diagram where actions are organized in a graphic flow. Binary decisions are used to control the flow. The Flow Chart Editor has full support for connectors and sub-programs. Actions and tests can be programmed in LD, ST or IL. The graphical editor allows each symbol to be resized independently, and automatically arranges the chart during development.


More Information

For more information call 800.831.7223 or contact This email address is being protected from spambots. You need JavaScript enabled to view it.