ProSoft Technology MVI56-101S - Manual (Page 150)

Reference MVI56-101S ♦ ControlLogix Platform
User Manual IEC 60870-5-101 Slave Communication Module
Page 150 of 193 ProSoft Technology, Inc.
August 2, 2011
Example - Event Priority
If the module is configured with the example values above, and the event queue
contains the events generated in the following order:
Event Order ASDU
1 M_SP_NA
2 M_SP_NA
3 M_DP_NA
4 M_ST_NA
5 M_DP_NA
6 M_SP_NA
Then, the module will respond to a Class One data request from the controlling
station by returning the data in the event queues in the order shown in the
following table.
Packet Order Content
1 M_DP_NA events 3 and 5
2 M_SP_NA events 1, 2 and 6
3 M_ST_NA event 4
WARNING: Events from the higher priority (lower-numbered) queues are always reported first,
when present, before lower priority (higher-numbered) queues. If careful planning is not exercised
when deciding how to configure Event Priority queues, or if large volumes of events occur events in
the lower queues may be lost due to buffer overflow.
When using Event Priority, events from the highest priority queues, when
present, will always be reported before events from lower priority queue.
Therefore, if large volumes of events are generated, events in the lower priority
queues may be lost due to event buffer overflows.
If the Set Priority Queue parameter is set to NO, this feature is not utilized.
Events will be reported based on their order of occurrence, as determined by the
event's timestamp. Multiple events will be assembled into message packets for
transmission. This methodology limits the likelihood of a buffer overflow and still
maximizes the bandwidth usage on the communication channel.