Rockwell Automation PLC-5 Fieldbus Solutions for Integrated Architecture User Manual - Manual (Page 47)

Publication 1757-UM006A-EN-P - May 2002
Integrating Fieldbus into Rockwell Automation Logix System 2-3
Fieldbus Interface Modules - The Key to an Integrated System
The 1757-FIM, Fieldbus Interface Module is the key to bringing the
Foundation Fieldbus system into a ProcessLogix system. The FIM has
been designed to operate as a stand-alone Foundation Fieldbus
interface or as a bridge between the ProcessLogix control
environment and the fieldbus devices. It supports both the
publish/subscribe and the client/server communication methods to
communicate with fieldbus function blocks. The control connections
must be downstream only.
The FIM is a doublewide module that plugs into a non-redundant
Controller or remote I/O chassis. It connects up to two Fieldbus H1
links through a companion Remote Termination Panel (RTP). These
independent links each have their own link schedule, link master and
time master functions. The RTP is designed for DIN rail mounting
within an enclosure. It optionally accepts a 24 Vdc input from an
external power supply to provide low-level power to fieldbus devices
on the H1 links.
The Fieldbus Interface Module functions as a dual network bridge
using a dynamic data cache to facilitate the exchange of data between
the ControlNet/Ethernet network and the Fieldbus H1 links. It
supports both publish/subscribe and client/server communications
methods to implement control connections between ProcessLogix
function blocks and fieldbus function blocks.
FIM capability includes converting ProcessLogix value-status structure
to fieldbus value-status by mapping similar fields to one another and
defaulting others. This means ProcessLogix can monitor fieldbus
control functions, fully integrate with control functions, or provide a
combination that includes using fieldbus based control as backup for
selected ProcessLogix control functions.
The FIM uses low and high priority send queues to make sure that
publish/subscribe data normally used for control is processed before
less important display access data. Publish/subscribe requests are
placed in the high priority send queue and client/server requests are
placed in the low one.