Allen Bradley EthernetIP specifics

[michael.lewchuk 0]

Hello. Is there any info out there for the specific EIP classes and operations supported by Allen Bradley PLCs? Allen Bradley PLCs "support CIP and EIP" but I find that a lot of what they do goes outside of the standard CIP/EIP classes. Generally I'm interested in commands that: * Browse the PLC's list of programmer-defined variables and modules with accessable I/O points * Demand read and write data * Subscribe to data updates if possible * Check PLC status Currently I'm having a problem with CIP return code 6. I'm querying the PLC and getting back "Partial transfer". How do I tell it to continue the transfer (i.e. request another page of data)? I find that there is a LOT of documentation on EIP, CIP, and so on, but when you look at it all, there's no real vendor-independent mandatory supported functionality for basic data access. Thanks.

[paulengr 44]

That's because the ODVA part of the CIP protocol is concerned with devices, not PLC's per se. All the questions you asked have to do with PLC's directly. AB has a document on their web site detailing how to do PCCC over Ethernet/IP. The "rabbit hole" you seek is in fact PCCC. PCCC is the Ethernet variant of DF-1, which is also well documented on their web site. They have also added a supplemental document explaining how to read/write the symbolic names that the ControlLogix family uses instead of using the "PLC-5 mapping" function. Through this function you will not be able to browse the tag database or utilize publish/subscribe but you can definitely poll variables and check PLC status. The one function I find most intriguing is the PLC-based alarm/event reporting system that thus far is only accessible through Allen Bradley's crappy OPC driver (RS-Linx). Beyond these basic functions it gets progressively more difficult. Part of this is so that Allen Bradley does not box themselves into a corner from a software point of view. A lot of what goes on in the ControlLogix processors is built into the compiler which is actually contained inside RS-Logix 5000. The Logix 5000 processor firmware is still very much in flux and is seeing new major firmware updates about once a year minimum. I have been using Rev 17. I recently had the pleasure of working on a Rev 15 system and several features were noticeably missing, but the Rev 10 processor was hard to recognize as the exact same equipment. Even the I/O cards are flash upgradeable, though most are only up to a major revision of 2 or 3 at the most.

[Arun Opto 22 0]

Perhaps you can try ODVA (www.odva.org). The full EIP specification is available there, but for purchase. They are supposedly vendor neutral so their documentation may have the vendor-neutral information you're looking for. FYI, FORM 1770 from Opto 22 (www.opto22.com), may be useful to you...though it specifically addresses EIP class accessability as related to using Opto SNAP I/O attributes over EIP.