Rockwell Automation Ethernet Design Considerations Reference Manual - Manual (Page 63)

Rockwell Automation Publication ENET-RM002C-EN-P - May 2013 63
EtherNet/IP Protocol Chapter 4
CIP Connection Message Types
CIP connections use one of the following CIP connection message types:
• Implicit
• Explicit
Implicit connections are time critical in nature. This includes I/O and
produced/consumed tags. Implicit refers to information (such as source address,
data type, or destination address) that is implied in the message but not
contained in the message.
Explicit connections are non-time critical and are request/reply in nature.
Executing a MSG instruction or executing a program upload are examples of
explicit connections. Explicit refers to basic information (such as source address,
data type, or destination address) that is included in every message.
CIP Connection Types
CIP connection types determine how CIP connections transfer data on the
network. The CIP connection types determine whether a connection is
established between devices. If a connection is established between devices, the
connection type determines if that connection remains open after data is
transferred.
There are two CIP connection types:
• Connected—Available with both implicit and explicit messages.
• Unconnected—Available with only explicit messages.
Table 10 describes how CIP connections are used with implicit and explicit
messages.
IMPORTANT CIP connections are further defined by these additional connection
parameters:
• CIP Connection Message Types
• CIP Connection Types