Software Modularity

IEC 61131-3 compliant programming tools provide the engineer with the opportunity to develop programs in Statement List, Ladder Logic, Structured Text and Sequential Flow Chart methodologies. Comprehensive built-in libraries of Function Blocks, Protocol Macros and Smart Active Parts (SAPs) greatly simplify the machine software development process, encouraging the re-use of code through Task-based programming.

SFC stands for “Sequential Function Chart” and is a sequential control system language used for machine process flow control. This lends itself to the repetitive control tasks often seen in numerous packaging processes. For a full overview, please see http://www.myomron.com/index.php?action=kb&article=17

Task-based programming greatly facilitates multi-author program development, allowing separate functional parts of the program, perhaps a specific motion control sequence, to be written by different developers, without the fear of conflicts with other parts of the program. Task-based programming offers the additional benefit of reduced PLC cycle time, as tasks may be executed only when required, thereby not adding to the scan time of the PLC whilst they are idle.

Protocol Macros are software ‘modules’ of communication sequences that allow the PLC to communicate with serially-connected devices. As well as a pre-written library covering such devices as Omron temperature controllers, visual inspection systems, RFID systems and modems, the user can develop his own communication sequences to almost any third-party serial device, via RS-232C or RS-422/485 connections. Once the macros have been constructed they can be re-used in the same, or any other program, thus reducing software development time.

Function Blocks (FB) are one of the most important components of the IEC61131-3 standard. Their main purpose is to promote well structured programming, re-use, and to allow complex programs to be built out of smaller and more manageable blocks of code that perform specific tasks. Omron’s extensive Function Block library greatly reduces software development time by providing proven and tested, pre-written software functions for many common control tasks. Function Blocks may be written in ladder or structured text code, and committed to the author’s own library for re-use within the same, or other, programs.