National Instruments BridgeVIEW 用户手册

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Appendix A
HMI Function Reference
A-16
© National Instruments Corporation
error indicates that an error occurred when executing Read Alarm Tag, or 
that the value returned by Read Tag Alarm is not valid.
shutdown indicates that the BridgeVIEW Engine is shutting down. In this 
case, the Read Tag Alarm VI no longer waits for a change in the tag alarm 
state
 and returns immediately with both timeout and shutdown TRUE. 
You can use shutdown to exit any loop that uses the Read Tag Alarm VI. 
changed? is TRUE when Read Tag Alarm returns a new alarm state from 
the Real-Time Database. If changed? is FALSE, the Read Tag Alarm VI 
probably timed out before the tag alarm state was updated. 
alarm message is the user defined string message displayed along with the 
alarm notification for a discrete tag. Notice that this output is not valid for 
any tag type other than discrete.