Rockwell Automation Publication 1444-UM001D-EN-P - June 2018 463
CIP Objects Appendix A
Behavior
The Voted Alarm Object provides for logical combinations of up to 4,
referenced, measurement alarms (instance attributes 25...28 refer). The alarm
logic scheme name (and logic description) applies to attributes in order, so
that:
X out of Y (where both X and Y are from 1 to 4) refers to attributes
25...28, unused attributes are ignored.
and for more complicated logic:
1oo2 AND 1oo2 is where the first pair refers to attributes 25 and 26 and
the second pair to attributes 27 and 28.
The alarm type, the measurement alarm behavior that is related to transducer
status (TX OK), determines how TX OK state is integrated into the voting
logic. 2oo2 illustrates an example of how that is reflected in the final logic (so
uses Alarm inputs 0 and 1):
• TX OK Considered - Alarm IF ([Alarm input 0 in alarm] AND
[Associated TX OK] AND [Alarm input 1 in alarm] AND [Associated
TX OK])
• TX OK Monitored - Alarm IF (([Alarm input 0 in alarm] AND [Other
TX Fail]) OR ([Alarm input 1 in alarm] AND [Other TX Fail]) OR
([Alarm input 0 in alarm] AND [Alarm input 1 in alarm]) OR [Both
TX Fail])
• TX OK Not Considered - Alarm IF ([Alarm input 0 in alarm] AND
[Alarm input 1 in alarm])
It is allowable for each measurement alarm to have another behavior that
pertains to transducer status. However, to avoid complicating the example, it is
assumed in the proceeding paragraph that both measurement alarms have the
same type.
Each Voted Alarm Object has up to three outputs, which are individually
enabled when required (Alert, Danger, dedicated TX OK). It is the enabled
outputs of the Voted Alarm Object that provide the 'actual alarms' that can be
assigned to relay outputs.
The (dedicated) TX OK output combines the relevant TX Status results in the
selected logic scheme. It does not pay any attention to measurement alarm type
setting (TX OK Considered, Monitored, or Not Considered).
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