Rockwell Automation 5720 DriveLogix System - Manual (Page 165)

Publication 20D-UM002C-EN-P - November 2003
Communicating with Devices on a ControlNet Link 7-19
• For a ControlNet bridge module (CNB) in a remote chassis, select the
most efficient communication format for that chassis:.
The Rack Optimization format uses an additional 8 bytes for each slot
in its chassis. Analog modules or modules that are sending or getting
diagnostic, fuse, or timestamp data require direct connections and
cannot take advantage of the rack optimized form. Selecting “None”
frees up the 8 bytes per slot for other uses, such as produced or
consumed tags.
• Separate the tag into two or more smaller tags:
– Group the data according to similar update rates. For example, you
could create one tag for data that is critical and another tag for data
that is not as critical.
– Assign a different RPI to each tag.
• Create logic to transfer the data in smaller sections (packets).
Producing a tag
Produced data must be of DINT or REAL data type or an array or structure.
You can use a user-defined structure to group BOOL, SINT, and INT data to
be produced. To create a produced tag:
1. You must be programming offline.
2. In the controller organizer, double-click the Controller Tags folder and
then click the Edit Tags tab.
3. Select the tag that you want to produce, or enter a new tag, and display
the Tag Properties dialog box.
4. Make sure the tag is controller scope.
5. Select the “Produce this tag” check box. Specify how many controllers
can consume the tag.
You can produce a base, alias, or consumed tag.
Are most of the modules in the
chassis non-diagnostic, digital
I/O modules? Then select this communication
format for the remote
communication module:
yes rack optimization
no none