Once RX register Debug Status bit 3 has asserted, data transmission has started.
Understanding of the JESD204 specification at this point resolves most data issues.
This article includes tips and tricks for particular devices and set-ups.
Debugging Data Transmission Issues:
K-characters in data
One common occurrence in data transmission is a high amount of K-characters being inserted into the data stream. This is due to alignment character insertion. When repetitive data is seen, alignment characters are inserted to ensure proper DC balancing.
K-characters are inserted to balance the voltage and the protocol understands the purpose of these characters. The other end of the receiver properly views the data.
With TI ADCs or DACs, it is very important that the correct control parameter is selected. If this is not the case, devices can show very subtle data errors.
On a waveform, this could show up as subtle jitter at the peaks of a wave.
If a sync signal cycles up and down, the link gets through the CGS and ILAS stages, but most likely a framing parameter is off (parameter mismatch).
Check for framing parameters on both ends of the link and ensure that they are matched (in particular, F, K, L and M).