I have a board that outputs an i2s signal (mclk at 49Mhz) using normal fliflops at output. Works perfectly when connected with short connections.
If I try connecting a cable at 10cm or more, I have some noise comming into the system.
My question is, should I use a buffer after the FFs to correct this ?
At 49MHz, a 10 cm cable becomes a long line and needs to be terminated to avoid signal reflections. The problem is that termination works well on point-to-point connections, and not so well on buses.
If your connection is unidirectional P2P, I would try to source-terminate all signals at the transmitter's side. Otherwise, you'll have to look at your signals with a scope to see what kind of noise you're getting exactly and what could be done to deal with it.
