BACnet Error - Request rejected by device. Reason: 9 (Unrecognized service).

I am using TOP Server to communicate with my BACnet device. The BACnet device is responding with BACnet Reject Code 9 in the TOP Server event log, which indicates "Unrecognized Service". What does this error mean and how can I resolve it?

BACnet Reject Code 9 is returned by a device with BACnet support when TOP Server has sent a request specifying a service that is not supported by the target device. All BACnet devices should have a document called a PICS (Protocol Implementation Conformance Statement) that defines which BACnet services it supports.

If you do not have the PICS for your device, you will want to contact the manufacturer or look on their website for this document. TOP Server supports the following BACnet services:

BACnet Service	BIBB*	Initiate	Execute
Who-Is	DM-DDB-A	X
I-Am	DM-DDB-A		X
ReadProperty	DS-RP-A	X
ReadPropertyMultiple	DS-RPM-A	X
WriteProperty	DS-WP-A	X
WritePropertyMultiple	DS-WPM-A	X
SubscribeCOV	DS-COV-A	X
SubscribeCOVProperty	DS-COVP-A	X
ConfirmedCOVNotification	DS-COV-A		X
UnconfirmedCOVNotification	DS-COV-A		X

*BACnet Interoperability Building Block (BIBB). This describes the services supported by a BACnet/IP device or application. For more information, refer to Annex K of the BACnet specification.

Once you have your device PICS, you can compare what TOP Server supports compared to your device to determine which service is being used that your device does not support.

Example:

Let's say your PICS indicates that your BACnet device only supports "ReadProperty" but not "ReadPropertyMultiple".

You would receive this error when using the default TOP Server settings for "Maximum Number of Items Per Request" (Default=16) whenever your client requests more than a single item at a time. You would have to change this setting to "1" to prevent TOP Server from ever requesting multiple items in a single request.

This example is only provided as an illustration of when you might receive this error. This error will be returned if TOP Server is using any of the above supported services that are not listed as supported in the device PICS.

Please contact technical support if you are unsure how to determine what services are supported by your BACnet device. Please be prepared to provide your device PICS and/or full make and model of your device.