User manual

Publication ENET-UM001I-EN-P - January 2010 95
Interlocking and Data Transfer Between Controllers Chapter 7
Tag Guidelines for
Produced or
Consumed Data
To properly organize tags for produced or consumed data (shared data),
follow these guidelines.
Terminology
A Logix5000 controller can produce (broadcast) and consume (receive)
system-shared tags.
To share produced or consumed tags, two controllers must be attached to the
same
EtherNet/IP subnet. Two controllers cannot bridge produced or
consumed tags over two subnets.
Guidelines for the Organization of Tags
Guideline Details
Create the tags at the
controller scope.
You can share only controller-scoped tags.
Use one of these data types:
· DINT
· REAL
· array of DINTs or REAL
s
· user-defined
• To share other data types, create a user-defined data type that contains the required data.
• Use the same data type for the produced tag and corresponding consumed tag or tags.
Limit the size of the tag
to
≤ 500 bytes.
If transferring more than 500 bytes, create logic to transfer the data in packets.
A size of < 125 DINT words will keep total bytes within 500. This helps reduce the total number of
packets for trans
actions.
Combine data that goes to the same
controller.
If producing several tags for the s
ame controller:
• Group the data into one
or more user-defined data types. This method uses fewer connections
than does producing each tag separately.
• Group the data according to similar update intervals
. To conserve network bandwidth, use a
greater RPI for less critical data.
For example, you could create one tag for data that is critical an
d another tag for data that is not
as critical.
Tag Definitions
Term Definition
Produced tag A tag that a controller makes available for use by other controllers. Mu
ltiple controllers can simultaneously
consume (receive) the data. A produced tag sends its data to one or more consumed tags (consumers) without
using logic. The produced tag sends its data at the RPI of the consuming tag.
Consumed tag A tag that receives the data of a produced tag. The data type of the consumed tag must match the
data type
(including any
array dimensions) of the produced tag. The RPI of the consumed tag determines the period at
which the data updates.