User Manual

Alarm management
Alarm response of the function blocks
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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.