What Are the Limits to Embedded XP?
For some time now, we have used a VxWorks real-time kernel with Windows NT to control five axes of motion. The specs tell us we can use XP Embedded without a third-party kernel, and, as a nice bonus, significantly reduce the memory-gluttony of NT. What does real-life performance experience tell us about whether this is a good idea?
From May 2005 Control Design
ANSWERS:XP Embedded Saves No Memory
We have run XP embedded and Windows NT embedded with the same real-time extension to the operating system. Our TwinCat is compatible without modification from NT Service Pack 1 through XP Service Pack 2. From our experience, XP Embedded requires as much or more memory than NT embedded does. XP Embedded is Binary-compatible to XP Professional and I believe that XP Embedded has the same real-time performance of XP Professional and requires a real-time kernel to run real-time software. We recommend a minimum 128 MB of RAM if Windows Embedded is to be run.
Windows CE has a built-in 1 ms real-time timing scheme, eliminating the need for a real-time kernel. CE also has a much smaller memory requirement. Our CX1000 embedded PC controller, which has been available since 2003, runs real-time XP Embedded or Windows CE. For XP Embedded, we run our real-time kernel. In the case of CE, it is not necessary to run the real-time kernel. The CX1000 controller with TwinCat can coordinate 4-6 axis of coordinated motion via Soft NC control (no motion controller card required). The system can perform 2 ms updates with about 40 us of jitter.
Rob Rawlyk, Applications and Engineering Manager, Beckhoff Automation, Minneapolis
Keep the Kernel
Windows XP Embedded is an excellent choice to use in combination with a real-time kernel, on its own may be a little more difficult especially if you require millisecond or sub-millisecond response times. Microsoft recommends that a third-party extension should be used for a hard real-time application. In my view, a hard real-time solution should be used in motion applications because a hard real-time operating system like B&R's Automation Runtime would guarantee the deterministic response required for todays motion applications.
John Roberts, Distribution Sales Manager, B&R Industrial Automation, Roswell, GA.
Novembers ProblemShould I Learn Object-Based Programming?
Im what some of your articles have referred to as a bit banger. Im a PLC ladder logic guy who knows he needs to get more current. I need a grounded understanding of what advantages I can get from becoming functional in object-based programming. I know reusability is a big plus, but can a few of you summarize its major advantages? How hard is it to learn, by comparison? Any downsides?
Send us your comments, suggestions, or solutions for this problem. Well include them in the November 2005 issue and post in on ControlDesign.com. Send visuals, tooa sketch is fine E-mail us at CDTheAnswer@putman.net or mail to The Answer to Your Problems, CONTROL DESIGN, 555 W. Pierce Rd., Suite 301, Itasca, IL 60143. You can also fax to 630/467-1124. Please include your company, location and title in the response.
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