Controllogix wire numbering methods


Thread Starter

T. Connolly

I am doing my first Control-Logix system. So far I am OK with it. What I typically would do with PLC-5 and SLC-500 systems is identify my wires by the plc address assigned to it. I am just curious, since the traditional I:00/00 or O:01/00 addressing does not really apply to the control logix PLC what are others doing for wire identification? A tag such as Local:2:I.DATA.0 seems a bit long for a wire ID.
I/O can also be identified by the slot of which the module resides, such as: An input module in slot zero I:0/0 for the first module in slot zero

Steve Myres, PE

Still numbering slot and bit, although I use the old TI "XY" notation. So a 32 point discrete module in slot 2 has X200 through X231. I even use this in applications where small PLC's are being used for remote I/O, as in X6100 = node 6, local I/O address X100.

Bouchard, James [CPCCA]

I have never liked the practice of using the PLC address as a wire number. When you need to change the address in the PLC you have to go out and change wire numbers on the devices ( we just had to do that because we had to move a module from one position to another ) the best approach is to assign numbers for the PLC devices just like you do for everything else otherwise you have two systems to maintain. Rockwell has proposed a numbering scheme for control logix but it is complicated and if you change the tag you have to go out and change the numbers on all the wires. Also when you eventually want to change the PLC to another brand or type ( ie PLC5 to CLX ) then you would have to change all the wire numbers. ( we have changed PLC's fortunately they did not use the address as a wire number in that case )

Sorry about the rant.

James Bouchard
As a panel builder, I find that the I/O address works the best ie: Ixx:yy/zz (I = in or out, x = rack, y = slot, z = point). Regardless of what you choose to do within the program the addressing of the card should not change once it has been wired. The norm is to design the panel around the program not vice versa, that way the changes needed to be done in the field are minimal.
You can use a tag such as "DI01"(DINT data type) Alias Local:2:I.DATA So you can get the DI01.0 to DI01.15 wire label.
In the program you can alias "motor_run" to DI01.0 again. In my project use the wire numbering method. (about 2000 points)

Tag Name (motor_run)
Alias For (DI01.0)
Base Tag (Local:2:I.DATA.0)

C. Thomas Wiesen

I worked on an assembly line with multiple stations along a conveyor 3 Controllogix processors and 8 DeviceNet Scanners
There was a large master set of drawings for power and global control stuff with individual drawing sets for each station.

I used the format: <Station Number>_<Sheet Number><Line Number>

Station Example: 12000_3562

We chose this since the hardware address had little meaning. All inputs were buffered to program tags, all outputs were aliased to program tags. The wire number was used in the buffered/aliased tag description. This provided a cross reference to the actual wire, the schematics, and the program.

C. Thomas Wiesen
Hello Mr Connolly:
I use a numbering system that I have not had any problems with when switching between instruments or motor control wiring. The following letters should come from the instrument letter designation table used by 99% of industry eg. A=analyzer B=burner etc. so everyone recognizes the cable by it's identifier, the same as a loop L-109 is a level loop. Note E is
already used in the inst table so I use Q
First assign a letter for electrical cables eg. Q
Second assign a letter for instr cables eg. I
or a letter for thermocouple cables eg. T
Now start at cable eg. Q00001/01----50 which is cable (elect) 00001 with conductors 1 to 50
The same applies to instrument cables
These cable numbers c/w destination (to & from), cable size , number of conductors etc should be maintained on a spreadsheet to avoid duplication
with only say 2 people with access to give out Numbers
If you change the equipment number or the instrument number or the module number and use the old cable no field re- numbering will ever be required.
Just change the cable numbers on the drawing / equipment number or what ever is required.
Make a quick schematic/loop and make some changes to see it works. This works for any PLC or Inst loop or motor control drawing.
Sorry for the babbling.
PS when you start your spreadsheet start with at least 0000 (max 9999 cables) or (00000) max 99999 cables They add up quickly so don't be shy.