Rockwell Automation Logix5000 Controllers Produced and Consumed Tags Programming Manual - Manual (Page 36)

Chapter 2 Produce a Large Array
When the offset value in array_packet[123] is different than the offset value in array_ack[0], the controller has begun to
receive a new packet of data; so the rung checks for the value of -999 in the last element of the packet.
If the last element of the packet equals -999, the controller has received an entire packet of new data and begins the copy
operation.
• The offset value moves from the packet to array_offset.
• The COP instructions copy the data from the packet to the destination array, starting at the offset value.
• The offset value moves to array_ack[0], which signals that the copy is complete.
• Array_ack[1] resets to zero and waits to signal the arrival of a new packet.
If the last element of the packet is not equal to -999, the transfer of the packet to the controller may not be complete; so -999
moves to array_ack[1]. This signals the producer to return the value of -999 in the last element of the packet to verify the
transmission of the packet.
Transferring a large array as smaller packets improves system performance over
other methods of transferring the data.
36 Rockwell Automation Publication 1756-PM011F-EN-P - October 2014