Rockwell Automation Logix5000 Controllers Produced and Consumed Tags Programming Manual - Manual (Page 31)

Chapter 2
Produce a Large Array
The Logix5000 controller can send as many as 500 bytes of data over a single
scheduled connection. This corresponds to 125 DINT or REAL elements of an
array. To transfer an array of more than 125 DINTs or REALs, use a
produced/consumed tag of 125 elements to create a packet of data. You can then
use the packet to send the array piecemeal to another controller.
When you send a large array of data in smaller packets, you must be sure that the
transmission of a packet is complete before the data is moved into the destination
array.
• Produced data over the ControlLogix backplane is sent in 50 byte segments.
• Data transmission occurs asynchronous to a program scan.
The logic that this section includes uses an acknowledge word to make sure that
each packet contains new data before the data moves to the destination array. The
logic also uses an offset value to indicate the starting element of the packet within
the array.
Because of the offset and acknowledge elements, each packet carries 123 elements
of data from the array, as shown in the following.
Introduction
Rockwell Automation Publication 1756-PM011F-EN-P - October 2014 31