Siemens SIMATIC S7-1500 Automation System System Manual page 151

Threshold mechanism for time error OB request
The OB parameter "Enable time error" is used to specify whether the time error interrupt
should be called when a specific overload level is reached for similar events.
If yes (check box selected), you use the OB parameter "Event threshold for time error" to
specify the number of similar events in the queue at which the time error interrupt should be
called. If this parameter has the value 1, for example, the event DW#16#0002:3502 is
entered once in the diagnostics buffer and the time error interrupt is requested when the
second event occurs. Additional diagnostic buffer entries of the event DW#16#0002:3502
that refer to this event source are suppressed until all events from this source have been
post-processed.
In the event of an overload, you therefore have the option of programming a reaction well
before the limit is reached for similar events and thus before the events are discarded.
The following value range applies to the "Event threshold for time error" parameter: 1 ≤
"Event threshold for time error" ≤ "Events to be queued".
S7-1500 Automation System
System Manual, 01/2013, A5E03461182-01
Basics of program processing
13.2 CPU overload behavior
151