10.1 Fieldbus Technology; Open Communications Architecture; Figure 36 Osi Versus Fieldbus Communication Model; Appendix A - Honeywell Series A User Manual

10.1 Fieldbus Technology

Open communications architecture

F Fieldbus is an enabling technology for dynamically integrating dedicated
OUNDATION
field devices with digitally based control systems. It defines how all "smart" field devices
are to communicate with other devices in the control network. The technology is based
upon the International Standards Organization's Open System Interconnection (OSI)
model for layered communications.
As shown in the following figure, OSI layer 1 is the Physical Layer, OSI layer 2 is the
Data Link Layer, and OSI layer 7 is the application layer or the Fieldbus Message
Specification. A Fieldbus Access Sublayer maps the Fieldbus Message Specification onto
the Data Link Layer. Fieldbus does not use OSI layers 3 to 6, and layers 2 and 7 form the
Communication Stack. Also, the OSI model does not define a User Application, but the
Fieldbus Foundation does.
OSI Model
Application Layer
7
6
Presentation Layer
5
Session Layer
4
Transport Layer
3
Network Layer
2
Data Link Layer
1
Physical Layer

Figure 36 OSI versus Fieldbus communication model.

R400 Experion PKS Series A Fieldbus Interface Module User's Guide
July 2010

10. Appendix A

Fieldbus Model
User Application
Fieldbus Message
Specification
Fieldbus Access
Sublayer
Data Link Layer
Physical Layer
Honeywell
User Application
Communication
Stack
Physical Layer
377