Echelon i.LON 100 e2 Internet Server - Manual (Page 65)

i. LON 100 Internet Server Programmer’s Reference 5-21
5.2.1.4.2 Requesting Data Points by Type and Last Update Time
You can also reference the data points to be returned by their data point type, and time of
last update. This may be useful if you want to see which data points were updated during a
certain time period, or if you want to read the values of all data points of a certain type.
Table 11 DataServerRead Input Properties
Property Description
<UCPTdataPointType> Enter the type of data point you want to see information for. Enter NVL
for NVL data points, or NVC for NVC data points. Leave this property
empty to see all data point types in the <Result> parameter.
<UCPTstart>
<UCPTstop> Use these fields to specify a range for the last update time to the data
points that will be returned by the function. Both parameters are
optional.
If you only specify a start time, the function will only return the data
points whose value or status has been updated since the time specified.
This is useful when an application only requires the latest updates of
data points, and based on the activity of the data points requested, it
can reduce the size of the response SOAP message.
If you specify a start and stop time only data points whose last update
time is between this interval will be returned by the function. If you only
specify a stop time only data points whose last update time occurs before
the stop time will be returned by the function.
If you do not enter a start or stop time, the function will return all data
points requested, up to the count specified.
The <UCPTstart> and <UCPTstop> properties must be entered as
timestamps in local time, with an appended time zone indicator that
denotes the difference between local time and UTC. For more
information on this format, see Local Times and Coordinated Universal
Time on page 6-12.
<UCPTcount> Use this field to specify the maximum number of data point entries the
function will return. If this property is not filled in, the function will
return all data points requested, or data points whose last update
occurred within the interval defined by the <UCPTstart> and
<UCPTstop> properties.
NOTE: You should not attempt to read more than 100 data points with
a single call to this function.
<UCPTlifeTime> Optional. Use this property to determine whether the values of the data
points requested in the <Data> parameter will be polled before they are
returned. This is described in more detail earlier in the section.
The following example <Data> parameter requests that information for NVL data points
updated in July of 2001 be returned. Because the <UCPTcount> property is set to 20, the
function will include information for no more than 20 data points in the <Result> parameter.
The information contained in the <Result> parameter for each data point returned by the
function is described in the next section of this chapter, DataServerRead Output Properties.