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FS-8700-19_Metasys_N2 Driver Manual Page 12 of 51
FieldServer Technologies 1991 Tarob Court Milpitas, California 95035 USA Web:www.fieldserver.com
Tel: (408) 262-2299 Fax: (408) 262-2296 Toll_Free: 888-509-1970 email: support@fieldserver.com
Driver Data_Type
MN2_Type values
Point Type Known Value
2
Suggested Value
3
AI 1
AO 2
BI 3
BO 4
ADF 5
ADI 6
BD 7
If a large number of points are to be monitored, optimal efficiency is achieved by
using the COS mechanism instead of reading each individual point directly. An
N2Open device responds to a COS poll with a change record if a change has taken
place. On startup the device will report the state of all its points when it receives a
COS poll.
Three kinds of Map Descriptors are required for every node that is to be monitored
using COS:
• A COS initialization Map Descriptor with Function set to ARS and
MN2_Function set to COS_Enable. This Map Descriptor enables COS polling
of those points on the VMA for which Passive Map Descriptors exist.
• A COS polling Map Descriptor with Function set to rdbc and MN2_Function set
to COS.
• A Passive (i.e. Function set to Passive) Map Descriptor for every point on that
node that is to be monitored. Any COS records received will be stored to the
matching Map Descriptor data location.
See example in Section 4.4.5
Using Override and Release - VMA
It is normally not necessary to use the Override command explicitly as the
FieldServer automatically uses this command when the Current Value attribute of a
point is written. For any other attribute it uses the Write command. It will sometimes
be necessary to send a Release command to an overridden point, however. To do
this, a Map Descriptor must be configured with Function set to wrbx and
MN2_Function set to Release. Then, when any value is stored to the Map
Descriptor data location, the Release command will be sent to the VMA point
specified by the Map Descriptor.
Note: The VMA Release function only works for analog and binary inputs (AI and
BI). Outputs may be restored to their original value using an explicit write command.
2
For information only. Do not use Driver type for these, but specify AI, AO, BI or BO directly in the Data_Type field.
3
These values are believed to be correct for the corresponding point types, but no guarantee can be given at this time.