ProSoft Technology 5201-DFNT-BACNET - Manual (Page 27)

BACnet ♦ ProLinx Gateway BACnet Protocol Configuration
BACnet/IP Client Edition 2 Protocol Manual
ProSoft Technology, Inc. Page 27 of 52
November 24, 2010
Write commands have a special feature, as they can be set to execute only if the
data area associated with the write command changes. If the register data values
in the command have not changed since the command was last issued, the
command will not be executed. If the data in the command has changed since
the command was last issued, the command will be executed. Use of this feature
can lighten the load on the network. In order to implement it, set the Enable
parameter for the command to C
ONDITIONAL
. Care should be taken when using
this option, as the UDP protocol does not guarantee the delivery of each
message. Therefore, after the write message is executed and after its retry count
has expired, it will not be sent out again until the data changes in the gateway's
database. The remote device may never receive the write message. Because of
this problem, this option should only be utilized on networks where the message
is guaranteed to get through and be processed by the server.
The gateway supports numerous commands, allowing it to interface with a wide
variety of devices.
3.3.2 Commands Supported by the Gateway
The format of each command in the list is the same for all operations. The first
part of the record contains information relating to the communication gateway,
and the second part contains information required to interface with the BACnet
server device. The Client supports the two basic functions: read and write. Within
each of these, a single or multiple point function is also supported.
Care must be taken to configure the command list parameters to allow the
commands to interface with the server device and its database. The commands
will execute properly only if these parameters are set correctly.