A-B ControlLogix Data Capture


Thread Starter

David M. Osborn

I need to capture data at a relatively high rate (1 ms or less) in a ControlLogix motion control application. I've found that, for some unknown reason, Rockwell Software has not seen fit to develop the software to do this. There isn't even a white paper or application note available from RS. I've been told that I have to develop my own application with a routine in the controller to gather the data in an array in controller memory, then use RSLinx to pull the data into a spreadsheet. It appears that this will have a limit of about a 3 ms update time, which is much slower than I had hoped for.

Has anyone out there dealt with this situation before? Any advice or guidance? It's probably too much to hope for, but is there a third party software solution that anyone would be aware of to achieve my desired goal?

Dave Osborn
Butech, Inc.
Perhaps Rockwell has not seen a level of interest that justifies the need to develop this particular application. The market is what drives product development after all. If corporations like Rockwell were to develop products for which there was only a minute potential market they would not be in business long.

Peter Nachtwey

My company sells motion controllers that talk to ControlLogix PLCs using Ethernet and soon Profibus DP. The motion controller can gather data ( target, actual , output, status bit )synchronously to its control loop 1024 times a second. This data can then be transfered out of the motion controller using Ethernet to the ControlLogix, RSView, or to Excel using a free ActiveX control. However the RMC motion controller has its own setup software that has plot routines to display and print this data.

Visit http://www.deltacompsys.com

Download the free setup software with on-line manual

Example program using ControlLogix to control the RMC motion controller

Peter Nachtwey
[email protected]

Noticed your question - I dont have a direct resolution when using RS software, however I can recommend a product that does do what you're asking for (But Im sure that switching to another vendor was not at the top of your list). Yaskawa's MP series Machine Control products are ladder based and can update at a rate of 1msec standard, with two separate simultaneous scan rate settings available - High and Low. Essentially the MP products provide you with a Motion Controller and PLC in one box. The data capture can be performed either within the controller (to table registers) or from the programming environment called Motion Works. Yaskawa has just released Motion Works 4.05 which has an enhanced Ladder Editor. Any questions, send me an email.

Bill Faber
[email protected]

richard najres

I would map the data to an array using a counter pulsed every 1ms as the indirect address of the array. copy this data periodically via linx to a spreadsheet. of course the program in the controler will be tiny. enjoy.
> I need to capture data at a relatively high rate (1 ms or less) in a ControlLogix motion control application. << CLIP>>


This limitation is a well known problem with the MotionLogix implementation in the ControLogix architecture. The host processor (PLC) is setup to provide only coarse trajectory information to the MotionLogix board and as such 3msec is exactly what the system was designed to do and you will be hard pressed to improve on it for any length of time (buffers fill up quickly and loss of data is common). When benchmarking the MotionLogix controller, we found it neccesary to connect another motion controller with analog I/O to the encoders signals and analog outputs from the MotionLogix controller and use the second motion controller as a Data Acquisition system. This allowed us to see how good a job the MotionLogix did at managing coordination between two axes and synchronous assignment of I/O with Motion.

Ken Brown
Applied Motion Systems, Inc.

Khris Wright


You failed to mention how many axies you were running. In the Control Logix system, you are limited to about 1ms per axis course update rate. So if you have four axis, you will have roughly a 4ms course update. If you are using a 5550 processor, you will be hard-pressed to have a periodic task run consistantly at 1ms. bacause of the way the systems does backround tasks, 1 out of 10 interupts to that task will take longer than 1ms, 1.5ms is very stable. All of the motion data is available at this rate. If you use the 5555 processor, which runs motion about 30% faster, and array functions over 50% faster, your performance will be much better. NEED TO GO FASTER??? Use Softlogix 5800 and you have a 1ms course update for up to 8 analog axis or 32 SERCOS axis. Your capture speed will only be limited by your computer speed. We have seen programs run 100x faster on real fast PC's.

None of this is rocket science, you just need to understand how the Control Logix works.

BTW, seems like several of those that responded to your message have more interest in selling you something different than helping you. Although there are faster motion controllers out there, show me one that can intergrate everything in one package and provide you the support that AB distributers and Rockwell can!

Write back if you need more info.