as soon as you hit 7700 it will transmit, it won't wait to be interrogated by primary radar...is this correct?
I am sure that is wrong.
Also, extended squitter returns data only when interrogated.
If you set 7700, nobody might see you for x seconds, where x is the period of the radar(s). In fact they might not see you for 2x if they have spurious squawk suppression which they probably do because with the "knob" transponders one can set 7700 momentarily.