Get Single Attribute

Use this section while Defining a trigger for a Rockwell unsolicited message when you select Get Single Attribute command.

Unsolicited Logix Listener Get Single Attribute Command payload parameters

The following parameters are displayed on the trigger definition panel when the Get Single Attribute command is selected. The values entered in these parameters must match the values that were entered while defining the unsolicited message in the RSLogix 5000 software.

Parameter	Description
Class (Hex)	The type or class of object to which the service is to be sent.
Instance	The instance of the object to which the service is to be sent.
Attribute (Hex)	The attribute of the object to which the service is to be sent.
The Class, Instance, and Attribute parameters are used by the Rockwell driver as values to compare against a received Get Single Attribute unsolicited message. A trigger that matches all of these parameters will be run. The message will be dropped if there is no match.
Output Length	This is the total number of bytes of data the Rockwell driver will send back to the ControlLogix device to complete the unsolicited message.
Output Data Type	Select the data type that matches the data the unsolicited message is expecting.

As part of the trigger execution, the data to be returned to the Logix device must be specified. This is done by populating the Event.Variable.Data variable defined as a destination or output parameter in a trigger action. An example of this would be defining the Event.Variable.Data variable within the Destination parameter of a Set action.

When the trigger ends its status and the data set in the Event.Variable.Data will be sent back to the PLC. The MSG instruction “DN” or “ER” bit will be set. The “DN” bit will be set if the trigger completes successfully. Triggers that complete in an error state will return an error code to the Logix PLC’s ladder logic. The MSG instruction could complete with errors and this is signaled by the ER bit set.

Input Variables

Event Variable	Data type	Description
Attribute	UINT2	Attribute ID of the CIP Class Object found in the CIP message
Class	UINT2	Class ID within the CIP message of the Object
Instance	UINT2	The Instance value of the object in the CIP message
IP Address	STRING length of 32	The IP Address of the PLC that sent the message
Service Code	UINT1	The Service code associated with the CIP message

Output Variables

Event Variables	Data Type	Description
Data	Varies depending upon selection	The data sent by the PLC. The data type can be either 1, 2, 4 or 8 Byte, Integer data, or 4 byte floating point data, or String data. The length divided by the size of one item, will indicate the number of elements sent in the message. For example if the data length is 100 and the user is sending 4 byte integers, the message contains 25 items.
ResultStatus	UINT1	Return code to send back to the PLC. By default a value of 0 will be returned to the PLC.