Echelon LNS - Manual (Page 256)

LNS Programmer's Guide 242
resource file. See Chapter 6 for more detailed information on program IDs and scope
selectors.
The
FormatSpec
object contains a
Scope
property, a
ProgramId
property, an
Index
property, a
FormatName
property, and a
FormatType
property. To use these properties
to change the base type of a monitor point or data point, follow these steps:
1. Access the
FormatSpec
object for the monitor point or data point whose
base type you want to change.
Dim MyFormatSpec as LcaFormatSpec
Set MyFormatSpec = MyNvMonitorPoint.FormatSpec
2. Set the
Scope
and
ProgramId
properties to reference the device resource
files containing the definition of the base type you want to use.
MyFormatSpec.Scope = lcaResourceScopeMfg
MyFormatSpec.ProgramId = “8000010000000000”
3. Set the
Index
property if you want to identify the new type by its index
value within the resource file. Or, set the
FormatType
and
FormatName
properties if you want to identify the type by its name. Note that the
FormatType
property must be set to
lcaFormatTypeNamed
if you want
to identify the type by its name.
MyFormatSpec.FormatType = lcaFormatTypeNamed
MyFormatSpec.FormatName = “UNVT_color”
NOTE: If you pass an invalid type name to the FormatName property,
and then pass the FormatSpec object back to a data point or monitor
point, no exception will be thrown, although the FormatSpec object will
not reference a valid type. The LNS Object Server will use the previous
setting of the FormatName property to determine the data point or
monitor point’s type. You should note that if you read the FormatSpec
object in this situation, the FormatName property will still return the
invalid type name.
4. The FormatSpec object is not passed by reference. So, you must pass the
modified
FormatSpec
object back to the data point or monitor point for
the changes made in steps 2 and 3 to take effect.
Set MyNvMonitorPoint.FormatSpec = MyFormatSpec
Reading the FormatSpec Object
The
FormatSpec
object contains several properties you can use to determine how the
data stored in your data points or monitor points will be displayed. For example, you can
use the UnitsAdder and UnitsMultiplier properties to determine how the scaled
value of the data point or monitor point will be unit-converted for display as a formatted
value when your application reads the FormattedValue property. These factors can also
be used to determine how the formatted value units differ from the base units associated
with the data point type.
Table 9.5 introduces the other properties of the
FormatSpec
object. These properties are
read-only, and are set based on the type the FormatSpec object represents. See the LNS
Object Server Online Reference for more detailed information on these properties.