Rockwell Automation 1734-AENTR EtherNet/IP Network Configuration User Manual - Manual (Page 74)

74 Rockwell Automation Publication ENET-UM001L-EN-P - March 2014
Chapter 6 Interlocking and Data Transfer between Controllers
Connections for Messages Messages transfer data to other modules, such as other controllers or operator
interfaces. Each message uses one connection, regardless of how many modules
are in the message path. To conserve connections, you can configure one message
to read from or write to multiple modules.
These connected messages can leave the connection open (cache) or close the
connection when the message is done transmitting.
Cache Message Connections
Use the message’s execution rate to determine whether to cache a connection
or not.
Table 15 - Message Connections
Type of Message Communication Method Used Connection Used
CIP data table read or write CIP Yes
PLC-2, PLC-3, PLC-5, or SLC (all types) CIP No
CIP with Source ID No
DH+ Yes
CIP generic CIP Your choice
(1)
(1) You can connect CIP generic messages, but for most applications we recommend you leave CIP generic messages unconnected.
Block-transfer read or write Yes
Table 16 - Guidelines for Caching Message Connections
Message Execution Instruction Configuration
Repeated Cache the connection.
Important: Caching keeps the connection open and optimizes execution time.
Opening a connection each time the message executes increases execution time.
Infrequent Do not cache the connection.
Important: Not caching closes the connection upon completion of the message,
freeing up the connection for other uses.