Produce and Consume a Tag
Chapter 1
Rockwell Automation Publication 1756-PM011J-EN-P - February 2018
15
Guideline
Details
Consume Integers
Create a user-defined data type that contains these members.
Data Type
Description
DINT
Status
INT[
x
], where
x
is the output size of the
data from the PLC-5C controller. (If you
are consuming only one INT, omit
x
.)
Data produced by
a PLC-5C
controller
Limit the size of the standard tag
to 500 bytes.
If you must transfer more than 500 bytes, create logic to transfer the data in packets.
If the produced tag is over a ControlNet network, the tag may need to be less than 500
bytes.
Important:
Produced and consumed safety tags are limited to 128 bytes.
Use the highest permissible RPI
for your application.
If the controller consumes the tag over a ControlNet network, use a binary multiple of the
ControlNet network update time (NUT). For example, if the NUT is 5 ms, use an RPI of 5,
10, 20, 40 ms, and so forth.
Verify that Compact GuardLogix
5380, CompactLogix 5380,
CompactLogix 5480,
ControlLogix 5580, or
GuardLogix 5580 controller
projects containing multicast
produce tags are configured
correctly.
Take the following steps to make sure consumers of produce tags can connect:
•
For consumers running Logix Designer releases v17 and earlier that are consumers of
a producer from a Compact GuardLogix 5380, CompactLogix 5380, CompactLogix
5480, ControlLogix 5580, or GuardLogix 5580 controller:
•
Verify that all multicast consumed tags of a produce tag are configured with
the same RPI. If they are not, some consumers will fail to connect.
•
For multicast consumers running Logix Designer releases v18 and later, take one of
these steps:
•
Verify that all multicast consumed tags of a produce tag are configured with
the same RPI, or
•
Verify that all multicast consumers are configured to
Allow Consumed Tags
To Use RPI Provided By Producer
.
Combine data that goes to the
same controller.
If you are producing several tags for the same controller, group the data:
•
Into one or more user-defined data types. (This uses fewer connections than producing
each tag separately.)
•
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 and another tag for data
that is not as critical.
When a tag is shared over a ControlNet network, the tag must fit within the
bandwidth of the network.
•
As the number of connections over a ControlNet network increases,
several connections, including produced or consumed tags, may need
to share a network update time (NUT).
•
Since a ControlNet network can pass only 500 bytes in one NUT, the
data of each connection must be less than 500 bytes to fit into the
NUT.
Depending on the size of the system, there may not be enough bandwidth on
the ControlNet network for a tag of 500 bytes. If a tag is too large for the
ControlNet network, make one or more of these adjustments.
Adjust for bandwidth
limitations
