Technologies Computer Driver Instruction Manual
FS-8700-16 BACnet PTP Serial Driver Manual        Page 17 of 20 
FieldServer Technologies 1991 Tarob Court Milpitas, California 95035 USA Web: www.fieldserver.com 
Tel: (408) 262-2299 Fax: (408) 262-9042 Toll Free: 888-509-1970  email: support@fieldserver.com 
Appendix C.  Troubleshooting Tips 
Appendix C.1.  Debugging a BACnet connection – Hints and Tips 
•  Disconnect the FieldServer from the BACnet network when transferring images to the BCU. 
•  If duplicate object instances are accidentally configured in the FieldServer, the second call of 
the instance will overwrite the first one. This may cause a BACnet Object to be “lost.” 
•  If “Virtual_BCU_…” is not being indicated as the device description for the FieldServer on the 
BACnet SCADA system, then the FieldServer is not communicating with the SCADA system. 
If the present value’s name is being indicated, but the present value shows question marks, 
then it is most likely that the Client side of the FieldServer is not communicating. 
•  When  new  points  are  added  to  the  FieldServer  it  is  important  to  restart  the  Summit 
Workstation or BCU, otherwise these new points may not be seen by the FieldServer. 
• 
Polling BACnet  addresses  that  are  not configured for  Lieberts  systems may cause  the 
connection to fail in older versions of Lieberts.  Please contact your Lieberts supplier for 
more information.
• 
When a BACnet_PTP connection is established, and the connection is broken abruptly 
(for instance a power down), the BCU might not know immediately that this happened. If 
the FieldServer is the powered up again, it might take several seconds (up to 60 
seconds) before polling will start again. 
• 
Extra  memory  is  required  to  store  Map  Descriptors  that  have  the  active/inactive  text 
parameters specified.  If the defaults are appropriate, do not specify these parameters. 
This will save memory and allow more Map Descriptors to be created
•  McQuay Units are shipped with a default Device instance of the last 6 digits of the McQuay 
Serial number. 
Trane Specific Tips 
•  When new points are added to the FieldServer it is important to restart Summit Workstation 
or BCU, otherwise these new points may not be seen by the FieldServer.  
•  Disconnect the FieldServer from the BACnet network when transferring images to the BCU 
Appendix C.2.  BACnet Specific Statistics 
Stat  Description  Resolution 
Link Control 
A  who-is  link  control  message  was 
send or received. 
It  is  normal  to  receive  a  few  link  control 
messages.    If  the  number  is  higher  than 
the transmit/receive messages, there may 
be a problem with lost communications. 
Unsupported 
Properties 
A  request  for  an  unsupported 
property was received. 
This is not an error.  BACnet clients often 
poll  all  properties  of  a  particular  object  to 
determine which properties are supported. 
Segmentation 
Not Supported 
Data  was  requested  but  the 
response  would  have  exceeded  the 
maximum  size  of  the  APDU  and 
could  not  be  sent  using  an  un-
segmented message. 
This is not an error - the BACnet client will 
use  a  different  method  to  read  data  from 
the FieldServer. 
Sequence Error 
Invoke  ID  of  a  reply  did  not  match 
the Invoke ID of the poll. 
You  should  not  see  this  message.    It 
normally indicates a configuration error. 
Write  Access 
Denied 
Writing to an object was denied. 
This typically happens when trying to write 
to  an  Input  Object  that  is  not  Out-Of-
Service.  It is not possible to write to Input 
Objects. 
Exception 
Errors 
A  BACnet  Service  was  denied 
because it is not supported 
This  may  be  a  problem  on  the  Client 
system.    Consult  the  PIC  statement  to 
determine what services are supported. 










