I/O addressing Compactlogix L32E

sirhiss2

Member
Join Date
Oct 2003
Posts
109
Hi guys, I'm reading through the manuals and I'm not sure I understand fully what they are trying to say about addressing the I/O using RSlogix5000. Lets say my PLC had the processor first (required) then the power supply, I/p card and o/p card. If I wanted to address, lets say, the third bit on the i/p card. The manual says "Location:Slot:Type.member.submember.bit". So would I be correct in saying "Local:1:I.3". I'm not sure what the member means?!? How would you address an analog card if I had a standard 2 channel analog i/p card after the descrete o/p card in my rack?

I also noticed that the Tag addressing is somewhat different. It says start with Tagname. etc.

Am I correct in saying that If I use Tag Names instead of addresses that the plc will automaticly assign internal addresses to these?

Can someone explain I/o addressing to me and provide a few examples so that i can get the full sense of whats happening here?o_O
 
First assign the cards to the rack in order under I/O Configuration. Once that is done look in 'Controller Tags' and scroll down to the 'local' area. Find the slot and keep opening by clicking on the '+' signs. You should see the points you wish to address. When programming a contact just double click above it to open a selection window. You can scroll down to the appropriate item and select it. No thought about format involved.
 
Just to expand on what Bernie said:

If you have RSLogix5000, just configure your I/O in RSLogix5000. As you add cards to the I/O configuration, tags are automatically added to the controller tags. You do not have to create these tags.

To actually use the I/O in programs, you have bascially 3 options.

Use the tags directly like is common practice in a PLC-5. But the tag names are long and ugly, not a very popular choice.

Alias each I/O point using a descriptive tag name. Pretty popular choice, very similar to using symbols except the alias is actually in the processor.

Map the I/O tags into members of udt structured tags. Also pretty popular, my personal favorite.

The processor takes care of allocating memory for any tags you create. The actual memory address for a tag is not used at all.
 
Thanks guys. That makes things alot easier.(y) I figured there would have to be some way of just selecting the address you want. Just a question, What do Member mean...What are they talking about with regards to this?o_O I was thinking it has to do with the type of data 'bool', integer, etc..
 
sirhiss2 said:
Thanks guys. That makes things alot easier.(y) I figured there would have to be some way of just selecting the address you want. Just a question, What do Member mean...What are they talking about with regards to this?o_O I was thinking it has to do with the type of data 'bool', integer, etc..

From the manual:
Member
An element of a structure that has its own data type and name. Members can also be structures creating nested structure data types.



Basically it means you can have nested UDT's as part of the tag name. For example:

ST.Setup.Number_of_Components (this is a tagname)

'ST' is a UDT (member)
'Setup' is also a UDT (in this case a sub member)
'Number_of_Components' is the bit


Hope this helps.
 

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