Rockwell Automation Publication 1756-PM011J-EN-P - February 2018
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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.
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Produced data over the ControlLogix backplane is sent in 50 byte
segments.
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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
