RSLogix 5000 data file advice/preference

[bobwithdana]

To answer your question as to why we do the analog scaling with the PLC logic is again a standard. We have over 200 PLC systems here and every Analog card is scaled from 0 to 100. Anytime I need to replace an analog card I just scale it from 0-100 and the PLC scales it for the device. Look at the Analog UDT. Everything, Scaling, alarm values etc are there.Im not saying this is the best way to program, Its not as important how you structure your logic as it is to make them all the same. Could you imagine training a new PLC Tech or even your graveyard electrcian on troubleshooting over 200 PLC systems that are all different. Indirect addressing and such.

 

[TConnolly]

What will happen if you add to the UDT. For example, a UDT has 30 bools and 12 DINTs. Then 10 bools and 4 DINTs are added. Would this be a problem?

Look down at the bottom of the window when the UDT editor is open. You will see a move up and a move down button. You can select any UDT element and move it around within the UDT with thse buttons to group Bools together or re-arrange elements as seems logical.

In your particular example as it is stated, you can leave the original 30 bools grouped together and then group the new ten together for the same memory footprint as grouping all 40 together. This is because bools 0 to 31 will consume 4 bytes. Then next 32 to 63 bools will consume 4 more bytes. Your ten extra bools will cross the word boundary after you add the second new bool anyways.

If however you were adding just one BOOL instead of ten and failed to group the BOOLS then your UDT would be four bytes larger than a grouped UDT.

Clear as mud?

 

[automatic]

I tend to use ISA standards for my tagname convention.

Can you please provide the standard number? I searched the ISA website and only could find some tag naming guidelines for PackML applications.

 

[TConnolly]

ANSI/ISA-S5.1-1984(R1992)

You can find a simplified table here:
http://www.plctalk.net/qanda/showpost.php?p=158326&postcount=9