Echelon SmartServer 2.2 - Manual (Page 262)

SmartServer 2.2 User’s Guide 263
Max Send Time
(Heartbeat) This property applies to output data points. You can enter the maximum
period of time (in seconds) that may elapse without an output data point
receiving an updated value from the SmartServer. If this time period
expires without the output data point receiving an updated value, the
SmartServer will automatically send the output data point an updated
value even if the value has not changed.
For example, if the value of a SNVT_temp data point is changing 1º every
10 seconds, but this property is set to 2 seconds, the SmartServer will
update the data point every 2 seconds—regardless of the fact that the
value is not changing more than once every 10 seconds.
An input data point connected to this output data point can use this value
as a heartbeat, as it will be able to detect a failure if it does not receive an
update within the specified time.
The default value is 0, which means that the SmartServer will only update
the output data point when its value changes. In addition, this default
value disables the functionality of the Max Receive Time property.
Note: The heartbeat should be approximately a fourth of the MaxReceive
Time of any bound input data point located downstream. For example, if
the heartbeat of the output data point is 5 seconds, the MaxReceiveTime
of any bound input data point should be 20 seconds. This allows for lost
messages.
Min Send Time
(Throttle) This property applies to output data points. You can enter the minimum
period of time (in seconds) that must elapse between updates transmitted
by the output data point. Setting this property reduces network traffic by
limiting the number of data point updates that are sent by the output data
point.
For example, if the value of a SNVT_temp data point is changing 1º every
0.5 seconds, but this property is set to 2 seconds, the data point will only
transmit the updated value every 2 seconds—regardless of the fact that the
data point value is changing more frequently than that.
If the data point value changes more frequently that the specified throttle,
only the first and last updates are propagated to the network. For example,
if the throttle is set to 5 seconds, and 4 updates occur within a 5-second
period, only the first and fourth updates will be propagated to the network.
The default value is 0, which means that output data point will send an
update every time its value changes.
Max Receive Time
(Offline) This property applies to bound input data points. You can set the
maximum period of time (in seconds) that may elapse without the input
data point receiving additional updates from the data point to which it is
connected. If this time period expires before the input data point receives
another update, the input data point will use its default value and its status
will be set to AL_OFFLINE. You can have an Alarm Notifier send an
alarm notification any time this occurs. See Alarming in Chapter 7 for
more information on how to do this.
The default value is 0, which means that a bound input data point will not
use its default value and its status will not be set to AL_OFFLINE if it
does not receive additional updates.
Note: The MaxReceiveTime of an input data point should be
approximately four times the heartbeat of any bound output data point
located upstream. For example, if the MaxReceiveTime is 20 seconds,