AD9959. We were trying to input an 80 MHz reference clock to our AD9959, but the board cannot recognize the existence of the clock input. We have checked jumper position, and found it correct according to manual. One possibility we are worrying about is that we burnt the reference clock channel by inputting 5 V peak-to-peak clock in the very beginning, which is larger than the maximum allowed input of the reference clock channel. Do you think the channel is damaged? What else do you suggest us to try to make it work? Moreover, what kind of waveform do you suggest as a reference clock, sinusoidal or TTL? Do we need to offsetting the signal to make it non-negative?