ControlLogix 5550 buffer size


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I am trying to read a tag from ControlLogix 5550 which has a size greater than the buffer size of the PLC(511 bytes). Im using the CIP protocol for doing the read. Is there any method by which i can read the tag in one single instruction ? If i need to read the tag using multiple reads, can we do the same via CIP ? As far as i know, we can read a particular element of an array tag using CIP, but i did not find any documentation that says that i can read a range of elements in an array tag using a single read command. I certainly appreciate any pointers in this regard.




You're on the right track, but you aren't going to get around that 500 byte limit for one tag with one instruction. Tips for accomplishing your goal--- moving a large chunk of data--- are in Chapters 14 and 15 of the Common Procedures manual, which you can view at

Hope this helps!

Larry Lawver
Rexel / Central Florida