User Manual

Alarm management
Alarm sources
9
136 | 351 CM110664en_07
● AlarmCollection object
● Discipline I/O
1, 2
● Trend Log / Trend Log Multiple
● Group
1, 2
● Device Info object, which models the properties of an automation station as a complete entity
● Loop object
Key
1
Discipline I/Os, Groups, Time Scheduler and Trend Log Multiple support only system alarms, that is, only alarms of the
FAULT type. Both function blocks can transmit more than one system alarm. The parameters [Rlb] and [MsgTxt] provide
detailed information about the cause of the most recent alarm message. The messages are transmitted in the order in which
they occur, irrespective of the importance of the alarm.
2
These function blocks only exist in Desigo PX.
Only these alarm sources incorporate Intrinsic Reporting, and can thus generate their own alarms. If any
other value of a function block needs to be monitored for an alarm (e.g., the control signal for a controller
block), an Event Enrollment object must be added.
Alarm-generating function blocks include a range of interface variables which can be set as parameters to
determine the alarm response (Input Property) or to supply the relevant alarm state information (Output
Property). These interface variables are described further below. Some of the interface variables are
common to all alarm-generating block types, while others are specific to certain types of alarm-generating
blocks.
Alarm state machine in an alarm-generating function block
Alarm state machine
The response in the event of an alarm is modeled by an alarm state machine. Each alarm-generating block
incorporates an alarm state machine of this type. The alarm-related interface variables can therefore be
used to define the response of this state machine, to simulate state transitions, or to represent the current
status of the state machine itself.
Alarm state event states
The alarm state machine can assume one of three basic states (event states [EvtSta]):
● NORMAL: There is no alarm condition present
● OFFNORMAL: Alarm caused by an OFFNORMAL condition
● FAULT: Alarm caused by a FAULT condition
With analog blocks, the OFFNORMAL state is explicitly subdivided into the sub-states HIGH LIMIT and
LOW LIMIT, which are described in detail further below.
The current state of the alarm state machine in an alarm-generating block is displayed externally in the
form of the output variable [EvtSta] (event state) of the block concerned.