General sequential function charts editor

Sequential function chart formalism is one of the 5 languages for PLC (programmable logic controller) programming described in the IEC 61161-3 standard. Many PLC vendors integrate their own SFC editor implementation as a part of their development environment. Absence of a universal SFC editor lead to the authors own development. This paper describes some of the features of the developed universal SFC graphical editor, which includes: 1. editor architecture; 2. graphical user interface; 3. SFC schema validation and compilation to various targets; 4. editor customization and integration to development tools of various control systems. REX uses the SFC editor in two ways: 1. a design tool for the ATMT, EATMT and REXLANG function blocks; 2. as an online visualization and debugging tool.