FBM233 FOXBORO
addition,PLC has increased sufficient internal resources such as timers,counters,internal relays,registers,and storage areas,bringing great convenience to programming.
programming language
IEC61131-3
Due to the differences in instruction systems and different user requirements for programming methods among PLC manufacturers,IEC has developed the Windows based programming language standard IEC61131-3(International Standard IEC1131 for Programmable Controllers issued by IEC in 1993)
specifies five programming languages:Instruction List(IL),Ladder Diagram(LD),Sequential Function Diagram(SFC),Function Block Diagram(FBD),and Structured Text(ST).This includes both textual programming(IL,ST)and graphical programming(LD,FBD),while SFC can be used in both programming languages.IEC Technical Committee(TC65)has come to carry out
The IEC61499 project extends IEC61131-3,which is a standard for the architecture of modular distributed systems interconnected through
communication internetworking,and will improve IEC61131-3.This is a standardized document based on digital technology for programmable logic control devices to move towards openness at a high level,and is a major trend in the development of PLC.
Development Trends
One or more PLCs are connected to a PC computer to form a system,which serves as the original programmer and human-machine interface operation station.This new trend in the 1990s brought business opportunities for system integration.At the same time,programming software,human-machine interface software(monitoring software or configuration software),and software interfaces(or driver software)have also been developed.
PLC manufacturers have gradually added various communication interfaces and provided a complete communication network on the basis of providing physical layer RS232/422/485 interfaces on the original CPU template.Due to the rapid development of data communication technology,users have strong requirements for openness,and the synchronous development of fieldbus technology and Ethernet technology,the PCS system composed of PLC is slightly better than the current situation of DCS’s openness.Rockwell AB has formed a multi-layer structure system,including Ethernet Net,Control Net,Device Net
