I can run the AD9625 in 8 lane mode (Fs=1400 MHz) and 4 lane mode (Fs=700MHz) without any problems. If I try running in 2 lane mode ( Fs= 350 MHz) with no changes to the hardware setup other than changing the clock speed, I get all zeroes as the data, with an occasional non-zero value. Both 8 lane and 4 lane mode show the correct analogue signal.
In all cases, the AD9625 is first reset then configured using the quick config register for all modes, with any unused lanes disabled and then a SYNC is issued to the ADC. The transmitter link is disabled prior to the setup of the AD9625 and then re-enabled prior to the sync being issued. The Rx side of the serial link runs at the same speed for all three modes so never changes and needs only to be reset . All clocks are running and stable prior to adjusting the AD9625.
The FACI characters (/A/ and /F/) are clearly visible with the correct periods and are present only in the lanes that I expect them to be but data is all zeroes in between, despite an analogue signal being present at the ADC input.
Is there something required in addition to setting the quick config register and lane enables to get the 2 lane mode to work?