The REF-clock is distributed by an AD9508, also the Master-Sync_out signal is distributed by an AD9508.
The IO-Update signal is synced with the Master-Sync-Clock via D-FlipFlops and is applied to all DDS simultaneously all the time.
All traces are length-matched. The REF-Clock-signals are in phase, also the Sync-in signals are in phase.
I do the sync procedure described in AN-1254.
Everytime i do the sync sequence, i get the same fixed phase offsets between the 4 channnels.
The phase offsets are constant.
I tried to change the the SYNC_OUT delay on the Master (Reg 0x1B [5:3]) to sync the REF-Clock to the SYNC-IN but i always get phase-offsets between the output signals.
If i skip step 5 (AN-1254) "set the CAL with SYNC-bit (Reg 0x1B )" and perform another DAC CAL to each device, i get random-phase-offsets.
I think, there is some kind of synchronisation, but i always get these fixed phase-offsets.
Unfortunately i cannot check the SYNC-Clock outputs of all four DDS-devices.
Is my setup in general correct?