Hollywood Hype and EDS

HollywoodThere’s a lot of hype in Hollywood. Lots of people are drawn into a theater to see a new movie with hype like this: “It will alter the way Hollywood makes movies. It is the coolest movie in years, and the hottest movie in decades.” It’s “Spectacular!” and “Life-affirming!” “No one will ever be the same after watching it.” And it goes on and on.

EDS (Electronic Data Sheets) files are sometimes hyped like that. EDS files are the ASCII files that describe an Adapter device to the network. (Scanners can have them too but they’re of little importance there.) The EDS files describe what the device is, its model number, revision and most importantly, the size of the I/O Assemblies. It also describes all the Objects in the Adapter, what attributes exist, if they are readable or writable and, if the vendor wants to be complete, the range of values for each of these attributes.

The concept of an EDS file got customers excited back when EtherNet/IP was new. It looked like this file would move the heavy lifting of providing a configuration tool. And since everyone using EtherNet/IP has RSLogix, EtherNet/IP vendors, integrators and end users all thought that there would be a common configuration tool for Adapters built into RSLogix.

Well, that never happened. The truth was that until a few years ago, an EDS file was necessary for the Conformance Test Lab but was actually of little use in the field. I had to explain this over and over to lots of customers in the last 10 years –many more times than I wanted.

EDS files are very important and a key component of an EtherNet/IP Adapter device. I really like how EDS files are handled by the Logix tools. Rockwell has done a pretty good job on this. There is a network browse facility that can search for EtherNet/IP devices on the network and let you automatically add those Adapters to the PLC scanlist. Rockwell Automation calls this Automatic Device Configuration which makes it sound a lot more sophisticated than it is.

EtherNet/IP Adapter devices fall into a couple of different categories depending on the level of sophistication of their EDS files:

ADAPTERS WITH NO EDS FILE – These devices typically come from third-party vendors with no relationship to Rockwell Automation. The EDS may not exist or not be available. Nothing you can do for these devices. It can find the device on the network and automatically capture the TCP/IP Address, but that’s all. The I/O Assembly Sizes for these devices must still be entered manually. The I/O Assemblies must be manually assigned to simple blocks of some data type (Ints, Dints, Floast…etc). And the Configuration data, the block of data that a ControlLogix PLC sends to an Adapter with the EtherNet/IP Forward Open, must be entered manually.

THIRD-PARTY ADAPTERS WITH AN EDS FILE – Rockwell calls these devices EDS AOP where AOP means Add On Profile. Besides populating the IP Address, it can now also automatically populate the I/O Assembly Sizes. And instead of manually selecting the assembly data types, they can get populated from the EDS file. (A vendor has to make that information available in the EDS file.) Configuration data is still entered manually, and there is no way to access the I/O Assemblies other than as an array of raw data.

ADAPTERS FROM AOP PARTNER EDS FILES – Rockwell provides special functionality for devices from vendors accepted into its AOP program. They call this functionality Add On Profiles (AOPs as opposed to EDS AOPs). AOPs allow RSLogix to not only find and load the IP Address and Assembly Sizes, but also to define the Assemblies as a series of Tags for ease of use in the Controller. Configuration data can be defined for loading when the Forward Open is issued. A configuration wizard exists to walk the user through configuration of the Adapter.

ADAPTERS FROM CLOSE PARTNERS’ EDS FILES – This is the “gold standard” for Adapters. These devices work identically to Rockwell devices. They are known devices; you can simply use the pull down to select them, just like a Rockwell Automation device. Only the closest of close partners to Rockwell get this service.

EDS files are important to EtherNet/IP. They’ve been around forever, and you can have really simple ones or really sophisticated ones. It’s up to the vendor of the EtherNet/IP Adapter.
An EDS is like one of those movies that you should see, but aren’t really looking forward to because you don’t think it will be all that great. EDS files are exactly like that. They are just something you’ll have to deal with when you do EtherNet/IP.