Appendix A
HMI Function Reference
©
National Instruments Corporation
A-63
Write Tag
Use the Write Tag VI to update the Real-Time Database with a new value for memory, output,
and Input/Output tags. The value also is sent to the server if it is an output or Input/Output
tag. If the tag is an input only tag, the Write Tag VI causes a system error because input tags
only can be updated by servers. If the tag is configured as an Input/Output tag, the tag value
is passed to the server when Write Tag VI is called but not written to the RTDB. The RTDB
is updated with the new value when the server polls it and passes it back to the BridgeVIEW
Engine. This maintains correct time synchronization in the RTDB.
tag name is the name of the output tag.
value is the value to be written to the output tag.
generate event (F) determines whether a user change event is generated
for the write operation on the tag. If the tag is configured with event logging
on, this tag event can be displayed in the Event History Display in your
HMI and logged to a .
evt
file. By default, generate event is FALSE.
status returns the current status of the value written in the Real-Time
Database. If status is greater than or equal to 0, the Write operation was
successful. If status is less than 0, either the device server has reported an
error indicating there is a problem with the tag, or BridgeVIEW has
reported an error indicating there is a problem using the tag.
error indicates that an error occurred when executing the Write Tag VI, or
that the status of the tag is bad. See status for the specific error condition.
shutdown indicates that the BridgeVIEW Engine is shutting down. In this
case, Write Tag no longer waits for tags to be updated and returns
immediately with both timeout and shutdown TRUE. You can use
shutdown to exit any loop that uses the Write Tag VI.
