The only "true" asynchronous notification available on TSU9600 is the TCP/IP socket. Everything else (RS232, Power Sense) has to be polled.
And as Dave says, the asynch is only valid if the unit is not asleep. The way to prevent the unit from going to sleep is to leave it docked 100% of the time or to enter setup and go one step above the 240second backlight limit and specify always on. Note that I'm not sure the remote does not enter sleep mode even with the backlight always on. This would need to be tested.
