Specifications

PlantScape OPC Support
PlantScape Server and Client Configuration Guide 439
How Items Access Point Parameters of Type enum
Some point parameters are enumerated—they can be represented by both an
integer and a string. Examples are: status point states, modes, and Control
Module Point enumeration parameters.
Two methods of accessing enumerated parameters are supported:
Parameter is written and/or read as text
This requires the item to be built with the enum flag on.
point.parameter /enum
Note If an item is built with /enum for which the enum flag makes no
sense, an empty string is returned.
Parameter is written and/or read as an integer
Enumerated type parameters can also be built without the enum flag. The
server will then read and write the appropriate integer value. It becomes the
responsibility of the client to convert the integer value into text if required.
Update Rates and Deadbands for Items
An update rate and a deadband can be associated with each item or group. The
update rate is the fastest rate at which the OPC Server will notify the OPC Client
of changes in data. The OPC Server will only notify the OPC Client of changes if
the data has changed by more than the deadband. The OPC Client can
automatically determine the update rate and deadband or it might require you to
configure it. You can normally specify any update rate and deadband in your
OPC Client, however, specifying high rates or low deadband values may put a
high load on the PlantScape OPC Server and the connecting network. If the load
is too high the PlantScape OPC Server will not return data at the requested rate.
Point Parameter Data Addressing
The following tables list the name of all parameters (for each point type) that can
be accessed via the PlantScape OPC Server. They also list the OPC type of each
parameter and indicate whether the parameter is read only.
Status Point Parameters
OPC Server Parameter Name OPC Type OPC Access Enumerated?
PV VT_I4 yes
Mode VT_I4 yes
Table 20.4 Status Point OPC Parameter Names and Details
plscpcg.book Page 439 Monday, May 28, 2001 10:11 AM