Unsolicited message handling

In the world of controllers and Communication Drivers, it is obvious that a controller will know when a critical event has occurred before the Communication Driver will have a chance to poll for that data. Therefore, it would seem natural that if a critical event occurs, the controller should have the capability to inform the Communication Driver immediately, without having to wait for the Communication Driver to poll it.

This is the role of an unsolicited message. After a controller has determined that a critical condition exists, it can generate a message immediately sent to the Communication Driver without a prior request from the Communication Driver. The unsolicited message implementation requires both the messaging instructions properly programmed in the controller logic and the device group appropriately configured in the Communication Driver.

Note: The use of unsolicited messages requires configuration changes in the controller. Please refer to the related Rockwell Automation documentation for procedures to set up unsolicited messages from the supported controller processors.

The ABCIP Communication Driver supports unsolicited messages from the following processors:

• PLC-5 and SLC 5/04 processors on the Data Highway Plus network.

  The following non-Logix processor configuration does not support unsolicited message handling:
  MicroLogix with 1785-KA5 via ControlLogix Gateway (1756-DHRIO and 1756-ENB).

• Logix5000 and MicroLogix 1100 processors on the Ethernet network.

  The following Logix5000 processor configuration does not support unsolicited message handling:
  CompactLogix going through the EtherNet/IP interface module (1761-NET-ENI).

• Logix5000, PLC-5, and SLC500 processors on the ControlNet network.

  The following SLC500 processor configuration does not support unsolicited message handling:
  SLC500 using 1747-KFC15 interface on ControlNet via the ControlLogix Gateway (1756-CNB and 1756-ENB) to RSLinx on Ethernet.

Configure the ABCIP Communication Driver to receive unsolicited messages

This option is available only to the controllers listed above.

1. Click on the target controller node under the controller branch of the Communication Driver hierarchy.

2. Select the Device Group tab of the configuration view.

3. Add a new device group or select an existing device group.

4. Right-click on the device group name, then select Edit from the shortcut menu.

   The Device Group Parameters dialog box is displayed.

   

5. In the Device Group Parameters dialog box, select the Support Unsolicited Messages check box.

6. Click OK.

   Note: Because the status of Support Unsolicited Messages check box cannot be readily viewed from the Device Groups tab, proper naming of device groups that support unsolicited messages is strongly recommended.

7. If appropriate, you can modify the Update Interval to "0".

8. Click Save to save the configuration change.

   Note: To enhance performance in message handling, the default for the device group is to not provide unsolicited message data; therefore, the Support Unsolicited Messages check box is not checked.
   The setting of this check box is hot-configurable. Unsolicited message handling will take effect in the Communication Driver as soon as the change made in the configuration view is saved.

Target-specific unsolicited messages

The Communication Driver supports target-specific unsolicited messages. This method involves sending messages to its target as specified by a given static IP address.

• Configure the appropriate message instructions in the controller with the proper path (including the destination IP address) for sending unsolicited messages.

• Configure the computer, in which the Communication Driver resides to receive unsolicited messages from the controller, with the corresponding IP address.

• Two instances of target-specific unsolicited messages are generated by the Communication Driver:

  • If the value of "Update Interval" for a topic is 0 (zero), the server will poll this topic only one time at the start. After that, only an unsolicited message will update the data.

  • If the value of "Update Interval" for a topic is >0 (greater than zero), the server will update the data for a particular item immediately upon receiving an unsolicited message for the item. The Communication Driver will also update the data at every Update Interval.

    Note: The Communication Driver requires unsolicited messages to be configured as "Connected" in Logix5000 processors. For details in setting the Allen-Bradley hardware for unsolicited messaging, please refer to the related Rockwell Automation documentation.

Receive unsolicited messages

9. Activate the Communication Driver.

10. Add the items, defined in the controller for unsolicited messages, for updates under the device group set up for receiving unsolicited messages.

Access the settings for device groups

11. Click on the target controller node under the Configuration hierarchy of your Communication Driver.

12. Select the Device Groups tab of the configuration view pane at right.

13. Right-click on the device group name, then select Edit from the shortcut menu.

Note: Unsolicited PLC-5 Typed Write using CIP with Source ID method from the Logix5000 processor is not supported. Instead, configure the message instruction with CIP Data Table Write using the CIP method from the Logix5000 processor.