Rockwell Automation Publication 1756-PM020F-EN-P - January 2019 17
Segment Type Value Byte Order Representation of Attribute ID Value (low byte first)
0 1 … n n+1
8-bit Attribute ID 0x30 Value N/A N/A N/A N/A
16-bit Attribute ID 0x31 00 Low High N/A N/A
See also
CIP services on page 13
Segment Encoding on page 16
CIP defines a way to reference items by their symbolic name. The segment
used is the ANSI Extended Symbol Segment defined in the CIP Networks
Library, Volume 1, Appendix C.
The Read/Write tags services can use these segments in the request path to
indicate which target tag to operate on. When addressing an arrayed tag, the
Logical Segment for Element ID is also used with the Symbolic Segment.
Segment Type Value
Byte Order Representation (low byte first)
0
1
… N N+1
ANSI Extended Symbolic 0x91 Length 1st char … Nth Char (1)
See also
Segment Encoding on page 16
All CIP services follow the Message Router Request/Response format
defined in the CIP Networks Library, Volume 1, Chapter 2. For complete
descriptions, see the CIP Networks Library. All requests take this form.
Message Request Field Description
Request Service Indicates to the object referenced in the request path to perform a task. The CIP or the
device manufacturer define these tasks. Most of the services covered in this manual are
defined by the Rockwell Automation vendor-specific objects, and are not found in the CIP
Networks Library.
Request Path Size A byte value that indicates the number of 16-bit words in the Request Path.
Request Path A variable sized field that consists of one or more segments. The path references the item
that services operate on in the controller. The path contains Logical or Symbolic segments
or both.
Request Data The service-specific data that is delivered to the object referenced in the Request Path. This
field only appears in the message frame if a service has service-specific data.
This same form is used for ControlNet and EtherNet/IP communication
CIP-based networks. Requests received through the serial port use another
protocol.
CIP Service Request/Response
Format
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