Omron NJ501-1300 - Preparing Derivative Data Types to Use CIP Communications Instructions

8-9
8 Message Communications
NJ-series CPU Unit Built-in EtherNet/IP Port User’s Manual (W506)
8-2 Using CIP Message Communications
8
8-2-5 Preparing Derivative Data Types to Use CIP Communications Instructions
In the CIP Common Specification, “Object,” “Class,” “Instance,” “Attribute” and “Service” are defined as
follows: (Source: CIP Common Specification)
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.)
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 Built-in EtherNet/IP Port for the
class ID, instance ID, attribute ID, and service code for each object.
To use CIP communications instructions, you must prepare derivative data type variables to input com-
munications parameter settings in advance. Refer to the
NJ-series CPU Unit Software User’s Manual
(Cat. No. W501) for the specifications and setting procedures for the variables that are described in this
section.
A CIP communications instruction combines all of the objects in a request path into a single structure
variable.
z Creating Structure Variables
To input a value into the structure variable of a CIP communications instruction, you must create a
user-defined variable with the same configuration in advance.
Term Definition
Object An abstract representation of a particular component within a device.
Class A set of objects that all represent the same kind of system component.
Instance A specific and real (physical) occurrence of an object.
Attribute A description of an externally visible characteristic or feature of an object.
Service A request from an external object (e.g., to read data).
8-2-5 Preparing Derivative Data Types to Use CIP Communications
Instructions
Providing the Structure Variables to Input Request Paths
.....
Example: Reading the Name of a Device
(Identity Object Class ID = 01)
Service Request
Get_Attribute_
Single
Destination
Class: 1
Instance: 1
Attribute: 7
Response
Product Name
Instance ID = 1
Attribute = 7
Device
Class ID = 1
Instance ID = 1
Attribute 7
Attribute 6
Attribute 1
Class ID = 2