I am working on positioning my org to move from RS500 to RS5000 and from RSView to FT SE sometime in the future before our next upgrade shuts us down.
Our PLC5s and SLCs have few symbols so I am working on an integrated tag structure.
When I first read the e-mail, I thought I had already written a post on this subject, but I went back and looked and I had really only discussed wire labeling and UDTs.
First, for those of you unfamiliar with Allen-Bradley products and what George is doing, he is converting programs written for SLCs and PLC5s (older, register-based platforms) into Control Logix programs written with RSLogix 5000.The Control Logix platform is tag based, there are no registers that you can see, just a big database full of text addresses for each data value.In the image at the top of this screen, the clip in the upper right is from a SLC500, it shows the Symbol and Description for an N7 (signed integer) register.While the address can be typed into the program either as N or TOT_060_FT52, only the address of N is present in the PLC processor.The symbol is kind of a “short cut” or mnemonic to make it easier to find and organize things.
RSLogix 5000 has a utility that converts SLC or PLC programs into Control Logix programs.It uses the symbol as the new tag name if a symbol is used, otherwise it converts to a name like “N7_40″ which isn’t very descriptive at all. It is just the part of the tag after the period or dot.A few limitations: SLC symbols can be only 20 characters in length, whereas Control Logix tags can contain 40 alphanumeric characters, not counting the dotfield. As George mentioned in his email, an AOI or Add On Instruction uses dotfields as part of it’s data definition, as does a UDT.Since the SLC is register based, it has no dotfields outside of those built into the data type, such as the preset for a timer (T. The clip to the left side in the image above shows a UDT called “Cake Recipe” which I used to create the elements Flavor, Lbs Flour etc. This tag list is part of the advanced course I talked about a few weeks ago.So these are a few of the constraints that will need to be followed when converting the programs; tag lengths will all be 20 characters or less (though they can be modified easily in Logix5000) and they won’t use UDTs unless you build new ones. And some AOIs may have to be built anyway since several instructions such as SCP (Scale w/ Parameters and DCD (Decode) are not present in the Control Logix.As far as naming conventions, I have used a lot of different ones in the past depending on the industry and who the customer was.