Omron CJ1W-EIP21 Operation Manuals page 216

8 Message Communications
Request Path (IOI)
In the CIP world, each device is modeled as a collection of objects. An Object abstractly represents the
specific configuration elements of a device.
Object
Object
Device
In the CIP Common Specification, "Object," "Class," "Instance," "Attribute," and "Service" are defined as
follows: (Source: CIP Common Specification)
Term
Object
Class
Instance
Attribute
Service
You use the Class ID, Instance ID, and Attribute ID to access an object.
You specify these three IDs to designate an object in a device. When you make a request from an
external device for a service, you must specify the Class ID, Instance ID, and Attribute ID. (The
Instance ID and Attribute ID are not required for some services.)
Example: Reading the Name of a Device
Service Request
Get_Attribute_
Single
Response
Product Name
These are called Internal Object Identifiers (IOI) because they identify the Class ID, Instance ID, and
Attribute ID within the device. Refer to 8-3 CIP Objects Sent to the EtherNet/IP Unit for the class ID,
instance ID, attribute ID, and service code for each object.
8-10
External request
(example: read)
Service
Object
An abstract representation of a particular component within a device.
A set of objects that all represent the same kind of system component.
A specific and real (physical) occurrence of an object.
A description of an externally visible characteristic or feature of an object.
A request from an external object (e.g., to read data).
(Identity Object Class ID = 01)
Destination
Class: 1
Instance: 1
Attribute: 7
CJ-series EtherNet/IP Units Operation Manual for NJ-series CPU Unit (W495)
Data
Attributes
Data
Data
Processing
Data
Object Instance
Definition
Class ID = 1
Instance ID = 1
Instance ID = 1
Attribute 1
Attribute 6
Attribute 7
Attribute = 7
Device
Class ID = 2