User manual

IEC61131 User and Reference Manual
April 22, 2008
493
generates unsolicited events for that Class. If unsolicited responses are enabled the controller
generates unsolicited events for that Class if its value or state exceeds a defined threshold. Valid
selections are:
 Enabled
 Disabled
Note that the controller does not transmit collected unsolicited messages (or responses) to a master,
even after the Hold Time or Hold Count conditions have been met, unless its 'Enable Unsolicited
Responses on Start Up' field is set to 'Yes' or the master triggers this transmission.
To configure a master to control unsolicited message transmission from a remote, see the Master
Poll configuration panel.
The Hold Time parameter is used only when unsolicited responses are enabled for a Class. This
parameter defines the maximum period (in seconds) the RTU will be allowed to hold its events
before reporting them to the DNP master station. When the hold time has elapsed since the first
event occurred, the RTU will report to the DNP master station all events accumulated up to then.
This parameter is used in conjunction with the Hold Count parameter in customizing the unsolicited
event reporting characteristics. The value used for the Hold Time depends on the frequency of event
generation, topology and performance characteristics of the system. The valid values for this
parameter are 0 - 65535. The default value is 60 seconds.
The Hold Count parameter is used only when unsolicited responses are enabled for a Class. This
parameter defines the maximum number of events the RTU will be allowed to hold before reporting
them to the DNP master station. When the hold count threshold is reached, the RTU will report to
the master, all events accumulated up to that point. This parameter is used in conjunction with the
Hold Time in customizing the unsolicited event reporting characteristics. To guarantee an
unsolicited response is sent as soon as an event occurs, set the Hold Count parameter to 1. The valid
values for this parameter are 1 - 65535. The default value is 10.
The Enable Unsolicited Responses on Start Up parameter enables or disables unsolicited responses
on startup. This affects the default controller behaviour after a start-up or restart. Some hosts require
devices to start up with unsolicited responses enabled. It should be noted this is non-conforming
behaviour according to the DNP standard. Valid selections are:
 Yes
 No
The default selection is Yes.
The Send Initial Unsolicited Response on Startup parameter enables or disables Send Initial
unsolicited responses on startup. This parameter controls whether an initial unsolicited response with
null data is sent after a start-up or restart. Valid selections are:
 Yes
 No
The default selection is No.
The Resend unreported events after parameter enables or disables the retransmission of events
after all attempts to report the events have failed.
Many communications networks experience occasional communications failures. In such networks,
even when message retries are used, there is a chance that some messages will fail – meaning there is