TABLE OF CONTENTS We will now review the main models and concepts defined in IEC 61499 to gain a general overview of the Function Block Standard. It is advisable to have some understanding of the material in this chapter before proceeding to any of the following chapters where we will review specific features of IEC 61499 in more detail.
Topics covered in this chapter include:
the system, device and resource models for distributed control systems
models for representing distributed applications
characteristics of function blocks and their execution
type specifications for different forms of function block
service interface function blocks to provide interfaces into hardware and operating systems
adapters for sharing block interfaces
textual syntax for defining IEC 61499 entities.
Before we proceed to look at the many models and concepts introduced by IEC 61499 in detail, let us reconsider the scope of the IEC 61499 standard as first discussed in the introductory chapter. Surprisingly the primary purpose of IEC 61499 is not as a programming methodology but as an architecture and model for distributed systems. There is no intention that the standard, as defined, will be used directly by programming tools. Instead, IEC 61499 provides a set of models for describing distributed systems that have been programmed using function blocks. This is an important distinction and must be understood to avoid many of the misunderstandings about IEC 61499.
If it does not let you program a distributed control system, how can it be of any use? IEC 61499 provides terminology, models and...
