Alarm Collection

The default value of [EnEvt] for the Alarm Collection object is FALSE, that is, [EvtSta] transitions are not notified.

An OFFNORMAL alarm is generated when:

  • The following applies to one or more alarm collection members:
  • [EvtSta] <> NORMAL and applies simultaneously for all these members: [StaFlg].Fault = false.

A FAULT alarm is generated when:

  • The following applies to one or more alarm collection members:
  • [StaFlg].Fault = true and therefore is set [Rlb] = UNRELIABLE_MEMBERS.

Analog Input, Analog Value, Analog Output

The Analog Input, Analog Value and Analog Output function blocks all have an identical alarm handling procedure.

The analog output function block also has a feedback value [FbVal]; however, this is not used for alarm monitoring. High and low alarm limits (variables [HiLm] and [LoLm]) are set for the OFFNORMAL alarms of analog objects. An OFFNORMAL alarm occurs either when the high alarm limit is exceeded, or when the current value falls below the low alarm limit. OFFNORMAL alarms are thus subdivided into two subcategories: HIGH_LIMIT and LOW_LIMIT. In addition, the variable [Nz] can be used to define a switching hysteresis for [HiLm] and [LoLm] to prevent over-frequent switching of alarms around the alarm limit.

Alarm response

An OFFNORMAL alarm is generated:

  • [PrVal] has either remained above the high alarm limit specified by the [HiLm] variable for a period of time longer than the period specified in [TiMonDvn]
  • or [PrVal] has remained below the low alarm limit specified by the [LoLm] for a period of time longer than the period specified in [TiMonDvn]

An existing OFFNORMAL (HIGH_LIMIT) alarm will disappear when [PrVal] has remained below the value ([HiLm] + [Nz]) for longer than the time specified in the variable [TiMonDvn].

An existing OFFNORMAL (LOW_LIMIT) alarm will disappear when [PrVal] has remained below the value ([HiLm] + [Nz]) for longer than the time specified in the variable [TiMonDvn].

  • A FAULT alarm is generated as soon as the [Rlb] property of the function block assumes any value other than NO_FAULT_DETECTED. In particular, this is the case when [Rlb] changes from a value not equal to NO_FAULT_DETECTED to another value not equal to NO_FAULT_DETECTED.
  • A FAULT alarm will disappear as soon as the [Rlb] property of the function block changes from a value not equal to NO_FAULT_DETECTED back to the value NO_FAULT_DETECTED.

BACnet Device Info Object

OFFNORMAL alarms

All the alarm-generating objects described so far model specific types of individual data points (physical or virtual). The BACnet device object by contrast, models the properties of an automation station as a complete entity. Alarm-relevant faults which cannot be allocated to a data point can be generated in an automation station (see the examples further below). This is why the BACnet device object includes an alarm mechanism. The alarm state machine and the alarm-related variables are essentially the same as for all the other alarm-generating block types. The difference lies in the possible causes of the alarm:

The alarm conditions described below cause the generation of an OFFNORMAL alarm in the BACnet Device Object:

Battery low

The battery in an automation station is checked periodically. An alarm is generated if the battery voltage is too low, or if the battery itself is missing. When the required voltage level is reached again, the alarm is reset with BATTERY_NOT_LOW.

RAM Pattern failed

This indicates that a memory-check error was found when the automation station was switched on. If no memory-check error is detected when the automation station is next switched on, the alarm will be reset.

Recipient not receivable

A recipient name (e.g., the configured recipient of an alarm) could not be resolved, because, e.g., the network connection to the recipient was interrupted. This causes an alarm to be generated. The alarm is cleared as soon as the subsequent name resolution process succeeds.

Notif. Class ref. missing

Each alarm-generating block includes a reference to a Notification Class block. If the referenced Notification Class block does not exist, the BACnet Device Object generates an alarm.

Life check error

While the life check is in progress, the primary server finds that it is unable to communicate with one or more of its backup servers (e.g., owing to a network failure). This causes an alarm to be generated. The alarm is cleared when, during a subsequent life check, all the backup servers are found again.

Primary server not found

This bit is set when the backup server detects that the primary server is no longer connected to the network. At the same time a notification (data-type STRING) is sent, defining the source, target and reason. The bit is reset as soon as the backup server detects the primary server on the network again.

FAULT alarms

The condition described below causes a FAULT alarm to be generated in the BACnet Device Object:

Flash is full

The automation station checks periodically whether there is at least one free page (64 kB) in the flash memory. This bit is set if the flash memory falls below this value. The bit is reset when the flash memory contains at least one free page again.

Alarm response of the BACnet Device Object is also parameterized or depicted by the number of variables, but the display differs: The BACnet Device Object is not displayed by a D-MAP function block, but rather only visible via BACnet. The variables described are therefore only accessible as properties of the BACnet Device Object.

Binary Input and Binary Value

The alarm handling process is identical for the function blocks Binary Input and Binary Value.

  • An OFFNORMAL alarm occurs when [PrVal] assumes the value specified by the variable [RefVal] for a time period at least equivalent to the delay time specified in the variable [TiMonDvn], [TiMonOff] or [TiMonOn].
  • An existing OFFNORMAL alarm condition will disappear (a) when [PrVal] assumes the value complementary to [RefVal] for a period at least equivalent to the period specified in [TiMonDvn], [TiMonOff] or [TiMonOn] or (b) when [EnAlm] is changed from TRUE to FALSE (see further below).
  • A FAULT alarm is generated when the [Rlb] property of the function block assumes any value other than NO_FAULT_DETECTED. In particular, this is the case when [Rlb] changes from a value not equal to NO_FAULT_DETECTED to another value not equal to NO_FAULT_DETECTED.
  • A FAULT alarm will disappear as soon as the [Rlb] property of the function block changes from a value not equal to NO_FAULT_DETECTED back to the value NO_FAULT_DETECTED.

Binary Output

The alarm handling process in the binary output function block is essentially different from that of the binary input and binary value blocks.

  • An OFFNORMAL alarm occurs when the current values of the variables [PrVal] and [FbVal] differ from each other for a time period at least equivalent to the delay time specified in [TiMonDvn], [TiMonOff] or [TiMonOn].
  • An existing OFFNORMAL alarm will disappear when the current [PrVal] und [FbVal] are again identical and remain so for a period at least equivalent to the time specified in the variable [TiMonDvn].
  • A FAULT alarm is generated when the [Rlb] property of the function block assumes any value other than NO_FAULT_DETECTED. In particular, this is the case when the [Rlb] property changes from a value not equal to NO_FAULT_DETECTED to another value not equal to NO_FAULT_DETECTED.
  • In the case of the binary output, [Rlb] errors may originate both from the [PrVal] (or associated physical output) and from the [FbVal] (or associated physical input).
  • A FAULT alarm will disappear as soon as the variable [Rlb] changes from a value not equal to NO_FAULT_DETECTED back to the value NO_FAULT_DETECTED.

Command Control

An OFFNORMAL alarm is generated:

  • A monitored, referenced object is not enabled
  • A referenced object cannot be enabled

A FAULT alarm is generated when:

  • A referenced object is not found
  • A referenced object is not a commandable object (output object or value object)
  • Invalid priorities are used for the referenced object (valid priorities are Priority 2, 5, 14 and 16)
  • ProgramValue or ExceptionValue are outside the permissible range
  • The referenced objects have a different number of operating modes
  • The function table is empty

Discipline I/Os and Group

Alarm response

Alarm handling is identical for Discipline I/O and Group blocks. These function blocks only support FAULT alarms.

  • A FAULT alarm is generated as soon as the [Rlb] property of the function block assumes any value other than NO_FAULT_DETECTED. In particular, this is the case when [Rlb] changes from a value not equal to NO_FAULT_DETECTED to another value not equal to NO_FAULT_DETECTED.
  • A FAULT alarm will disappear as soon as the [Rlb] property of the function block changes from a value not equal to NO_FAULT_DETECTED back to the value NO_FAULT_DETECTED.

The following conditions cause a FAULT alarm to be initiated:

  • Address conflict:
  • The subsystem fails to recognize the device defined in the [IOAddress] parameter. This alarm is issued by the associated function block.
  • Communications error:
  • The subsystem indicates a communications failure. This can be due to a bus open circuit or a faulty device, or, very rarely, to a communications overload on the bus. These alarms are indicated by the shared function block.
  • The subsystem indicates an inadmissible response from a device e.g. in the case of faulty QAX… room unit. These alarms are indicated by the shared function block.

Multistate Input and Multistate Value

The alarm handling process is identical for the function blocks Multistate Input and Multistate Value.

  • An OFFNORMAL alarm occurs when [PrVal] assumes one of the values specified under [RefVals] (list of multistate values) and remains at this value for a period at least equivalent to the time specified by the variable [TiMonDvn]. In particular, this applies when [PrVal] changes from one value in [RefVals] to another value in [RefVals].
  • An existing OFFNORMAL alarm condition will disappear either if [PrVal] reverts to a value not contained in the [RefVals] list, and retains this value for a period at least equivalent to the period specified in [TiMonDvn], or if [EnAlm] is changed from TRUE to FALSE (see further below).
  • A FAULT alarm is generated when the [Rlb] property of the function block assumes any value other than NO_FAULT_DETECTED. In particular, this is the case when [Rlb] changes from a value not equal to NO_FAULT_DETECTED to another value not equal to NO_FAULT_DETECTED.
  • A FAULT alarm will disappear as soon as the [Rlb] property of the function block changes from a value not equal to NO_FAULT_DETECTED back to the value NO_FAULT_DETECTED.

Multistate output

The alarm handling procedure for the Multistate Output function block is different from the alarm handling procedure for the Multistate Input and Multistate Value function blocks, but follows the same principles as for the Binary Output block:

  • An OFFNORMAL alarm occurs when the current values of the variables [RwVal] and [FbVal] differ from each other for a time period at least equivalent to the delay time specified in [TiMonDvn].
  • An existing OFFNORMAL alarm will disappear when the current [PrVal] und [FbVal] are again identical and remain so for a period at least equivalent to the time specified in the variable [TiMonDvn].
  • A FAULT alarm is generated when the [Rlb] property of the function block assumes any value other than NO_FAULT_DETECTED. In particular, this is the case when the [Rlb] property changes from a value not equal to NO_FAULT_DETECTED to another value not equal to NO_FAULT_DETECTED. In the case of the multistate output block, [Rlb] errors may originate both from the [PrVal] (or associated physical output) and from [FbVal] (or associated physical input).
  • A FAULT alarm will disappear as soon as [Rlb] changes from a value not equal to NO_FAULT_DETECTED back to the value NO_FAULT_DETECTED.

Power Control

An OFFNORMAL alarm is generated:

  • The UP command is issued but the maximum stage has already been reached
  • The UP command causes MaxPower to be exceeded
  • Table_No is set outside the admissible range

A FAULT alarm is generated when:

  • A referenced object is not found
  • A referenced object is not a multistate value object
  • Object_No. is outside the admissible range
  • StepLimit is outside the range of the referenced object
  • The function table is empty

Pulse Converter

Alarm response

An OFFNORMAL alarm is generated, when [PrVal]:

  • [PrVal] has remained above the high alarm limit specified by the [HiLm] variable for a period of time longer than the period specified in [TiMonDvn] (HIGH_LIMIT)
  • or [PrVal] has remained below the low alarm limit specified by the [LoLm] variable for a period of time longer than the period specified in [TiMonDvn] (LOW_LIMIT)

An existing OFFNORMAL (HIGH_LIMIT) alarm will disappear when [PrVal] has remained below the value ([HiLm] + [Nz]) for longer than the time specified in the variable [TiMonDvn]

An existing OFFNORMAL (LOW_LIMIT) alarm will disappear when [PrVal] has remained below the value ([HiLm] + [Nz]) for longer than the time specified in the variable [TiMonDvn]

  • A FAULT alarm is generated as soon as the [Rlb] property of the function block assumes any value other than NO_FAULT_DETECTED. In particular, this is the case when [Rlb] changes from a value not equal to NO_FAULT_DETECTED to another value not equal to NO_FAULT_DETECTED.
  • A FAULT alarm will disappear as soon as the [Rlb] property of the function block changes from a value not equal to NO_FAULT_DETECTED back to the value NO_FAULT_DETECTED.

Trend Log

Alarm response

The Trend Log function has an intrinsic reporting mechanism, but does not issue OFFNORMAL alarms.

  • A FAULT alarm is generated as soon as the [Rlb] property of the function block assumes any value other than NO_FAULT_DETECTED. In particular, this is the case when [Rlb] changes from a value not equal to NO_FAULT_DETECTED to another value not equal to NO_FAULT_DETECTED.
  • A FAULT alarm will disappear as soon as the [Rlb] property of the function block changes from a value not equal to NO_FAULT_DETECTED back to the value NO_FAULT_DETECTED.

Event message

An event is generated when:

  • The record count exceeds the record count value [RecCnt] set via the notification threshold [NotifThd], that is, the local non-volatile trend memory is overflowing.

Event enrollment

The event enrollment object monitors referenced BACnet properties in other objects. The referenced property can be located in the local device or in another device.

Event algorithms

Monitoring details for a property value are defined by means of event algorithms. An event algorithm has a specific parameter. Event algorithms are the same as for intrinsic reporting. Intrinsic reporting uses a subset of the possible event algorithms of event enrollment.

Event_Type

Event_State

Event_Parameters

Data type

CHANGE_OF_BITSTRING

NORMAL

OFFNORMAL

Time_Delay

Bitmask

List_Of_Bitstring_Values

Unsigned

BIT STRING

list of BIT STRING

CHANGE_OF_STATE

NORMAL

OFFNORMAL

Time_Delay

List_Of_Values

Unsigned

list of BACnetPropertyStates

CHANGE_OF_VALUE

NORMAL

Time_Delay

Bitmask

Referenced_Property_Increment

Unsigned

BIT STRING

choice {BIT STRING, REAL}

COMMAND_FAILURE

NORMAL

OFFNORMAL

Time_Delay

Feedback_Property_Reference

Unsigned

BACnetDeviceObjectPropertyReference

FLOATING_LIMIT

NORMAL

HIGH_LIMIT

LOW_LIMIT

Time_Delay

Setpoint_Reference

Low_Diff_Limit

High_Diff_Limit

Deadband

Unsigned

BACnetDeviceObjectPropertyReference

REAL

REAL

REAL

OUT_OF_RANGE

NORMAL

HIGH_LIMIT

LOW_LIMIT

Time_Delay

Low_Limit

High_Limit

Deadband

Unsigned

REAL

REAL

REAL

BUFFER_READY

NORMAL

Notification_Threshold

Previous_Notification_Count

Unsigned

Unsigned

CHANGE_OF_LIFE_SAFETY

NORMAL

OFFNORMAL

LIFE_SAFETY_ALARM

Time_Delay

List_Of_Alarm_Values

List_Of_Life_Safety_Alarm_Values

Mode_Property_Reference

Unsigned

list of BACnetLifeSafetyState

list of BACnetLifeSafetyState

BACnetDeviceObjectPropertyReference

EXTENDED

Any BACnetEventState

Vendor_Id

Extended_Event_Type

Parameters

Unsigned

Unsigned

Extended_Event_Type

UNSIGNED_RANGE

NORMAL

HIGH_LIMIT

LOW_LIMIT

Time_Delay

Low_Limit

High_Limit

Unsigned

Unsigned

Unsigned

Event notification

An event enrollment object also monitors the status flag property of an object with referenced property. If the FAULT flag of the referenced object is set, the event enrollment object generates a Fault alarm.

Loop object

Alarm response

The Loop object contains intrinsic reporting.

An OFFNORMAL alarm occurs when:

  • [XCtr] exceeds the limit (SetPoint + ErrorLimit) longer than the specified time (HIGH_LIMIT) defined in variable [TiMonDvn]
  • [XCtr] drops below the limit (SetPoint – ErrorLimit) longer than the specified time (LOW_LIMIT) defined in variable [TiMonDvn]

An existing OFFNORMAL alarm (HIGH_LIMIT) disappears again when [XCtr] drops below the value (SetPoint + ErrorLimit – Deadband) longer than the specified time defined in variable [TiMonDvn].

An existing OFFNORMAL alarm (LOW_LIMIT) disappears again when [XCtr] exceeds the value (SetPoint – ErrorLimit + Deadband) longer than the specified time defined in variable [TiMonDvn].

FAULT alarm:

  • A FAULT alarm occurs immediately as soon as [Rlb] of the function block has a value other than NO_FAULT_DETECTED. This is true in particular when [Rlb] changes from a value that is not equal to NO_FAULT_DETECTED to another value that is not equal to NO_FAULT_DETECTED.
  • A FAULT alarm disappears immediately as soon as [Rlb] of the function block changes again from a value that is unequal to NO_FAULT_DETECTED to the value NO_FAULT_DETECTED.