Controllogix Details

[robertus]

Rockwell supplies 'canned' logic for configuring communication between CN2FF modules and a controllogix plc. I have done this, all is working, however I am trying to get breakdown of the *_status and *_quality words.
They are both 8 bit words. the status word is generally 0 if all is healthy and the quality word is -128, -124 when healthy.
I am wondering if there is anyone out there who has details weather they are bit level or integer values to translate the words.
I've had no luck with either suppliers of instruments or with Rockwell.
I would imagine these words are a fieldbus standard and not specific to instruments, however I may be wrong.

[Heather Santos]

Hello robertus,

Status is part of the FF specifications, in particular you will find status defined in the FF-890-1.6 Function Block Application Process (Part 1) specification.

All input and output parameters have a value and status associated with them. Status validates the data and is propagated through the linked function blocks. The status is 8bits (1 octet), which is spilt into three parts, (2bits) quality, (4bits) sub-status, (2bits) limit. Quality indicates whether a value is good (non-cascade), good (cascade), uncertain, or bad. The sub-status bits indicate what caused the quality to change, for instance an active block alarm or fault state active. The sub-status is listed in Table 3 of FF-890-1.6.

If you have further questions, please contact me at heather.santos@fieldbus.org

[rkelly]

It seems like there are a few different ways to integrate Foundation Fieldbus into ControlLogix PLCs. There are two linking devices that I've seen - the 1757-FFLD (using RSFieldbus) and the 1788-CN2FF (using NI-FBUS configurator).

If anybody has some end user experience with FF on ControlLogix then I'd be interested to hear your thoughts - was it useful or is the engineering complex and time consuming?

[BruceB]

was it useful or is the engineering complex and time consuming?

I did a project with the FFLD and it is very time consuming and tedious to get everything working. I'd consider this software user vicious since at one point the PC's virus scanner kicked in for its daily scan and the RSFieldbus software crashed and deleted my project file! They describe using templates to shorten configuration but we were never able to make this work. All of the device configuration is done from the various Block sheets, Transducer Block, Resource Block, etc. so you need to understand a lot about the device before you start configuring it. I seem to recall that I also had to put each of the blocks in Auto to get them to run. Hopefully they've done a better job with the ControlNet version.

Bruce Brandt, P.E.
Engineering Team Manager
Bay-Tec Engineering, Inc.