User Manual

Alarm management
Alarm response of the function blocks
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● 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: