Rockwell Automation 1756-NEX Nexus Module - Manual (Page 94)

G-2 Glossary
Publication 1756-UM524B-EN-P - December 2008
Transaction A process within an application program (User Transaction) or a
system (System Transaction). Every transaction is identified by a unique Trans-
action Code (TCD).
Transaction Code (TCD) A unique number assign to each transaction (transac-
tion identifier). It is included in each ADP PDU header. The User Transaction
TCD range is from 1 to 59999. The System Transaction TCD range is from
60000 to 65534.
User Transaction A transaction within an application program. A TCD,
assigned by the user, is provided to ADP along with a message to be transmitted
and is included in a header of the PDU containing this message.