FAQs

1. What is IEC61131-3?
2. What is a POU?
3. What is a PAS POU?
4. What is an APPF?
5. What is a business object?

1. What is IEC61131-3?

During the last ten to fifteen years, many different languages have been used to write programs for industrial control applications and Programmable Logic Controllers (PLCs). This lack of standardization costs technicians, maintenance personnel, system designers, and plant managers both time and money. To correct this problem, a working group within the International Electro-technical Commission (IEC) was set up to look at the overall design of programmable logic controllers, including hardware design, installation, testing, documentation, programming, and communications. The IEC developed the IEC61131 standard to address all aspects of PLC design and IEC61131-3 is becoming the standard PLC programming language worldwide. IEC61131-3 covers the programmable languages Function Block Diagram (FBD), Ladder Diagram (LD), Sequential Function Chart (SFC), Structured Text (ST), and Instruction List (IL).

2. What is a POU?

IEC 61131-3 encourages well structured 'top-down' or 'bottom-up' program development. This standard allows a program to be broken down into functional elements that are referred to as POUs (Program Organization Units). Examples of POUs include functions, function blocks, and programs.

3. What is a PAS POU?

A PAS POU is a library of function blocks that have been developed by Yokogawa to facilitate the programming of control applications. These save users considerable time as the IEC61131-3 function blocks offer only the basic functions used in the IA field. (For example, advanced functions such as bump-less start have to be included in the PID block in the IA field even though the IEC function block does not have this function.) Users can easily construct the regulatory control logic and save time by combining PAS POU function blocks.

4. What is an APPF?

An Application Portfolio (APPF) is a group of Program Organization Units (POUs). These are control programs that have been developed over the years by Yokogawa, a leading vendor in the IA field. With an APPF, control logic can be easily developed and POUs from other user or system integrators can be widely shared. The following APPFs are currently available: PAS (function blocks for distributed control systems), SAMA, Communication (FA-M3, MELSEC, SYSMAC, power monitors, Temperature Controller, Boiler Control, Boiler Auxiliary), RS communication, and Ether communication.

5. What is a business object?

To meet the increasing demand for the sharing of information in real-time, we have developed a business object concept for dealing specifically with business information such as raw materials prices on the VDS and FCN/FCJ. This information is distinctly different from process parameters such as SV and MV. As the first such business object application, we have developed an Econo-Pilot energy saving system, and more such applications are planned.