Logix Tags / Connections

plc noob

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When using control/compact logix i see that produced and consumed tags use 1 connection each ( ETHERNET ) to the processor. Which is overloading me on conections.

Now moving this same tag data into a message instruction seems to free up those conections and seems to be about the same speed.

Speaking with AB they say produced/consumed is faster and that tags in message instructions use on connection per tag also.

I have to disagree as this is not what i see.

What is the max amount of dta / tags that can be transfered withone message instruction?

How many connections does a message instruction consume?
 
plc noob said:
When using control/compact logix i see that produced and consumed tags use 1 connection each ( ETHERNET ) to the processor. Which is overloading me on conections.

Now moving this same tag data into a message instruction seems to free up those conections and seems to be about the same speed.

Speaking with AB they say produced/consumed is faster and that tags in message instructions use on connection per tag also.

I have to disagree as this is not what i see.

What is the max amount of dta / tags that can be transfered withone message instruction?

How many connections does a message instruction consume?
Click to expand...
Publication 1756-PM0011-EN-P, logix 5000 controllers common procedure (Chapter 11) has the answers for all your questions.
By the way have tried to use an array as a produced tag or consumed, may be this will solve your connection problem.
 
In my previous reply, the subject, or title said to package the data into arrays. When the message text said see subject, that's what I was referring to. You can and should minimize the number of connections used when using produced/consumed tags by blocking them off into arrays. My statement was that of my opinion that doing this, even when not necessary, is good practice.
 
I have never setup the udt's in logix.

I do have different data types.

Anyone have any tips on UDT'S?

How many tags per udt? Only one connection per udt?

Are udt's faster or slower than produced consumed?

The message instructions i am using as temp fix seem to only use 1 connection but will this increase if i add more tags to the message instruction.

Are udt's better than the message instruction?
 
UDTs do not have anything to do with communication, so they are not faster or slower than messages or produced/consumed. UDT stands for User-defined Data Type. You are creating your own type of data, which is a collection of the basic data types, like DINT, STRING, FLOAT, and so on.

UDTs are useful to group related values of different data types. If you have a motor, you might want to know it's speed in RPM, it's temperature, etc. You can create a UDT that contains tags for this information all in a single place instead of creating multiple individual tags.

This website can explain what UDTs are and how they are used pretty well: http://www.plcdev.com/user_defined_data_types_udts_and_oop
 
Pandersen is right

pandersen said:
UDTs do not have anything to do with communication, so they are not faster or slower than messages or produced/consumed. UDT stands for User-defined Data Type. You are creating your own type of data, which is a collection of the basic data types, like DINT, STRING, FLOAT, and so on.

UDTs are useful to group related values of different data types. If you have a motor, you might want to know it's speed in RPM, it's temperature, etc. You can create a UDT that contains tags for this information all in a single place instead of creating multiple individual tags.

This website can explain what UDTs are and how they are used pretty well: http://www.plcdev.com/user_defined_data_types_udts_and_oop
Click to expand...


PLC Noob: Please download same manual as recommended before ( Publication 1756-PM001I-EN-P ) but this time read chapter 2.
 
Depending on the application, another advantage of Produced tags, is that they can be consumed by multiple clients. I still generally avoid them though, and go with the straight MSG instructions, mainly to avoid having to cross-populate my IO tree with processors.

And you have never used a UDT? They can be just about anything in makeup, and virtually any size. Using a UDT data type in a Produced/Consumed tag or a MSG instruction will send/receive everything contained in the UDT.

You can even include UDT's as members of UDT's (just not recursively).
 
rdrast said:
And you have never used a UDT? They can be just about anything in makeup, and virtually any size. Using a UDT data type in a Produced/Consumed tag
Click to expand...

A Produced tag is limited to 500 bytes of data...

500 SINTs
250 INTs
125 DINTs
62 LINTs
6 STRINGs
??? UDTs - depends on the individual UDT size
 

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