FieldServer LonWorks FS-8700-21 - Manual (Page 31)

FS-8700-21 LonWorks Manual Page 31 of 72
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Appendix A.7. Node Status Operation
When binding network variables on the FieldServer, the node status will be on-line before binding as well as after
un-binding network variables. A Node will go off-line only when a bound network variable of that node goes off-
line (e.g. is disconnected).
When using a network tool to commission the FieldServer (implicit addressing), the FieldServer LonWorks Node
must be placed ONLINE on the LonWorks network before it will pass data with other bound network variables. The
following messages may appear on the driver screen when using Ruinet which indicates that the FieldServer has
not been put into the ONLINE state yet:
"Not sending NV msg for [variable name], Node OFFLINE!"
To set the FieldServer to ONLINE using LonMaker:
Right-click on the FieldServer device and select Manage.
On the Devices Tab, click the ONLINE button.
The FieldServer LonWorks Node is always ONLINE when using explicit addressing.
Note: The FieldServer Node_Status function (refer to the FieldServer Configuration Manual) looks at the Node_ID
configured in order to monitor Node status. In implicit applications this may not be the real Node_ID since
Node_ID is allocated by the network manager.
Appendix A.8. Working with Binary Data
When sending binary data on a LonWorks network, there are two SNVT’s that are most commonly used, namely
SNVT_State and SNVT_Switch.
SNVT_State is a 16 bit integer that allows the user to send 16 data bits to the remote device. To do this, the 16
data bits need to be packed into an integer word. If this packing is already done when the value is transferred into
the FieldServer, then the SNVT need only be linked to the relevant Data Array offset for transfer out of the
FieldServer. However, if the FieldServer is picking up 16 separate bits from another network for this variable, then
the FieldServer Packed_Bit function can be used to achieve the packing. See the FieldServer Configuration manual
for more details on the Packed_Bit function.
SNVT_Switch is a two byte value consisting of an analog value in the left hand byte (VALUE portion), and a binary
state in the right hand byte (STATE portion). LonMark guidelines for this SNVT stipulate that the VALUE portion
has a range from 0-100%, and that the STATE portion can assume a value of 1 or 0. However, since the raw data
type for these two values is byte (a value ranging from 0-255), care needs to be taken when transferring values
into this SNVT to make sure the source values are within the legal range. If a value is placed into one of these
bytes that is deemed out of range, then a -1 value will be sent on the LonWorks network to indicate out of range.
Also note that when sending binary status in a SNVT Switch, some devices expect the VALUE portion to change
when the STATUS portion changes, so an analog value that changes in sympathy with the binary state may be
necessary.