Echelon i.LON 100 e2 Internet Server - Manual (Page 54)

5.2.1.1 DataServerList
Use the DataServerList function to retrieve a list of data points that you have added to the
i. LON 100 Data Server. The Data Server List function accepts an empty string as the
contents of its parameter. If you supply an empty string as the parameter,
the list returned by the function will contain an entry for every data point in the Data
Server.
Alternatively, you can specify a subset of data points to be listed by filling the properties
described in Table 9 into the parameter you supply to the function.
Table 9 DataServerList Input Properties
Parameter Description
Enter the type of data point to be listed in the return string (NVL or
NVC). Leave this property empty to display all data point types.
Optional. Enter a string of 16 comma-separated Boolean values. This
string will be compared to the string defined for
each data point. If at least one set bit in this string matches the
string defined for a data point, then that data point
will be included in the list returned by the function.
The property for a data point is defined when it is
added to the Data Server, and can be written to with the
DataServerSet function, which is described later in this chapter.
Enter the index number of the first data point to be listed in the
return string.
Enter the maximum number of data points to be included in the
return string.
The example below requests that the function return a list of up to 50 NVL data points,
starting with index number 0.
In this example, the function returns a element at the beginning of the return
string, because the requested in the input is NVL. This contains
global information about the data point type requested in the list. Or, if the property had
been filled in as NVC, a element would have been returned. Each of these
elements includes the following child elements:
• and . Child elements identifying the major and minor
version numbers of the firmware implementation the Data Server application is using.
• . A timestamp indicating the last time the Data Server was written
to. This timestamp is expressed in UTC format, as per the ISO 8601 standard.
• . This property defines how old (in seconds) the value of a data
point of the specified type can be before the Data Server retrieves a new data value
from the driver when an application requests the value of a given data point. If this
parameter is set to 0, the values of the data points will be copied from the i. LON 100
Data Server when an application requests them, and no update will be requested
from the driver. If this parameter is set to a positive value, the i. LON 100 Data
Server will poll the driver for the current value of a data point each time an
application requests it, and the time interval defined by the property has expired.
i. LON 100 Internet Server Program 5-10 mer’s Reference