Gary.Johnson

Relationship between CIP "implicit messaging" and addresses mapped to nodes in CJ1w-DRM21.

5 posts in this topic

Got a real head scratcher and I'm hoping for some guidance. I've been handed a system that communicates with field devices over Devicenet but instead of reading/writing CIO addresses the PLC and devices are exchanging hex codes via something called "CIP implicit messaging". I've pretty much figured out what CIP messaging is but the OEM didn't bother to provide a map of the specific addresses in use. I'm looking at an overcomplicated chunk of programming that employs multiple levels of indirection (for loops, index registers, pointers, arrays...) and no documentation to explain how everything works. Before I spend days/weeks trying to pry information out of the OEM or reverse engineer the entire system I'm hoping there is some sort of correlation between these CIP message addresses and the CIO addresses allocated to the nodes in CX-Integrator. Any insights?

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I think, similar to my post here you should be able to upload the configuration out of the DRM21, and see how the mapping is done between master and slaves. http://forums.mrplc.com/index.php?showtopic=28671&p=136759

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Thanks PdL, I did that when I was initially handed the system. The device(s) in question are Watlow EZ-Zone temperature controllers. The configuration in the DRM21 allocates four 8 bit registers as polled inputs and four 8 bit registers as polled outputs to each of the Watlow nodes. The EDS file supplied by Watlow shows 80 bytes one way and 84 the other. Some of the controllers are dual channel and require a minimum of 16 bytes in each direction to exchange the minimum information required to operate them. This leads me to believe that the configuration in the DRM21 has no bearing on CIP implicit messaging. I guess the next question I have is does this CIP implicit messaging operate independant of the I/O configuration in the DRM21 and if so, is it possible to (re)configure the devices to operate like normal Devicenet nodes or do I have to figure out how to exchange CIP implicit messages?

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I only used Devicenet for "static" mapping of slave IO to the master, so I don't know really. Where would the CIP messaging be configured, using which tool?

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Got it sorted out. "Implicit messaging" is ODVA's term for mapping memory areas of a given device to Devicenet master allocations. In the case of the Watlow devices it's a list of parameters like presets and temperature readings that are mapped to DRM21 addresses in order of appearance. The first parameter in the list is mapped to the first allocated address and so forth. Watlow provides a piece of software called ASSEMBLY PROGRAMMER for configuring their devices and you have to have it to use their temp controllers. The units as delivered can't be controlled over Devicenet. I suspected this but the manufacturer of the machine I'm working on mucked things up so badly that it was impossible to tell from his code. The fellow I spoke with at Watlow was an expert on their devices and how to configure them but wasn't much help trying to translate that into Devicenet. I had to configure a device, add it to the network and sift through PLC addresses until I stumbled onto the numbers I was looking for. Time consuming but it got the job done. Thanks again. Hope this helps the next guy who runs into these devices.

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