The Foundation protocol is designed to be compatible with the officially sanctioned SP50 standards project of the ISA, as well as the specifications of the International Electrotechnical Committee (IEC). Since its founding, the Fieldbus Foundation has made compliance with the ISA/IEC standards a priority.

The IEC voted to include the Foundation HI and HSE specifications in the IEC 61158 international standard. The CENELEC Technical Bureau added the Foundation H1 specifications to EN 50170 Euronorm. In addition, Foundation technology is the only implementation of the ANSI/ISA-50.02 standard.

The Foundation specifications are also compliant with IEC 61804 (Function Blocks for Process Control and Electronic Device Description Language) and IEC 61508 (Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems).

Both NAMUR (Germany) and JEMIMA (Japan) have voiced support for Foundation technology, and provided input from the end user community that aided in specification development.

Approval and support by key international industry bodies gave users the confidence that their investments in Foundation-compliant solutions were based on recognised global standards and sound best practices from industry groups.

The Foundation specification is based on the ISO/OSI layered communications model consisting of three major functional components: the physical layer, the communication stack and the user layer.

The physical layer corresponds to OSI Layer 1, which receives encoded messages from the upper layers and converts the messages to physical signals on the fieldbus transmission medium and vice-versa.

The communication stack corresponds to layers 2 and 7 in the OSI model. Layer 7, the application layer (AL), encodes and decodes user layer commands. Layer 2, the data link layer (DLL), controls transmission of messages onto the fieldbus through layer 1. The DLL also manages access to the fieldbus through a deterministic, centralised bus scheduler called the link active scheduler (LAS). The LAS is used for scheduling transmissions of deterministic messages and authorising the exchange of data between devices. The fieldbus does not use the OSI Layers 3, 4, 5 and 6.
 

Links