Route a signal to RTSI when AO starts output

[cooler]

I would like to route a signal to RTSI when AO starts output using "Route signal.vi".
Now I choose the signal source as "AO update" so that a series of TTL signals are routed to RTSI.
If I would like only to route a signal to RTSI when AO starts output,what option of signal source should I choose??
Thank you for you help!!

[L Aguila]

I will answer you question assuming you have an E Series Board.

The signal that should be routed to the RTSI line is the PFI6/WFTRIG signal. That is AO Start Trigger in the signal source and RTSI line in the signal name of the "Route signal.vi". You can find an explanation of the signal in the E Series User Manual, whose link is: http://digital.ni.com/manuals.nsf/websearch/CA6CAEC450BD7E3786256721007D6A30?OpenDocument&node=132100_US